20130618_2_reindex_concurrently_v27.patch

*** a/doc/src/sgml/mvcc.sgml
--- b/doc/src/sgml/mvcc.sgml
***************
*** 863,870 **** ERROR:  could not serialize access due to read/write dependencies among transact
  
          <para>
           Acquired by <command>VACUUM</command> (without <option>FULL</option>),
!          <command>ANALYZE</>, <command>CREATE INDEX CONCURRENTLY</>, and
!          some forms of <command>ALTER TABLE</command>.
          </para>
         </listitem>
        </varlistentry>
--- 863,871 ----
  
          <para>
           Acquired by <command>VACUUM</command> (without <option>FULL</option>),
!          <command>ANALYZE</>, <command>CREATE INDEX CONCURRENTLY</>,
!          <command>REINDEX CONCURRENTLY</> and some forms of
!          <command>ALTER TABLE</command>.
          </para>
         </listitem>
        </varlistentry>
*** a/doc/src/sgml/ref/reindex.sgml
--- b/doc/src/sgml/ref/reindex.sgml
***************
*** 21,27 **** PostgreSQL documentation
  
   <refsynopsisdiv>
  <synopsis>
! REINDEX { INDEX | TABLE | DATABASE | SYSTEM } <replaceable class="PARAMETER">name</replaceable> [ FORCE ]
  </synopsis>
   </refsynopsisdiv>
  
--- 21,27 ----
  
   <refsynopsisdiv>
  <synopsis>
! REINDEX { INDEX | TABLE | DATABASE | SYSTEM } [ CONCURRENTLY ] <replaceable class="PARAMETER">name</replaceable> [ FORCE ]
  </synopsis>
   </refsynopsisdiv>
  
***************
*** 68,76 **** REINDEX { INDEX | TABLE | DATABASE | SYSTEM } <replaceable class="PARAMETER">nam
        An index build with the <literal>CONCURRENTLY</> option failed, leaving
        an <quote>invalid</> index. Such indexes are useless but it can be
        convenient to use <command>REINDEX</> to rebuild them. Note that
!       <command>REINDEX</> will not perform a concurrent build. To build the
!       index without interfering with production you should drop the index and
!       reissue the <command>CREATE INDEX CONCURRENTLY</> command.
       </para>
      </listitem>
  
--- 68,88 ----
        An index build with the <literal>CONCURRENTLY</> option failed, leaving
        an <quote>invalid</> index. Such indexes are useless but it can be
        convenient to use <command>REINDEX</> to rebuild them. Note that
!       <command>REINDEX</> will perform a concurrent build if <literal>
!       CONCURRENTLY</> is specified. To build the index without interfering
!       with production you should drop the index and reissue either the
!       <command>CREATE INDEX CONCURRENTLY</> or <command>REINDEX CONCURRENTLY</>
!       command. Indexes of toast relations can be rebuilt with <command>REINDEX
!       CONCURRENTLY</>.
!      </para>
!     </listitem>
! 
!     <listitem>
!      <para>
!       Concurrent indexes based on a <literal>PRIMARY KEY</> or an <literal>
!       EXCLUDE</>  constraint need to be dropped with <literal>ALTER TABLE
!       DROP CONSTRAINT</>. This is also the case of <literal>UNIQUE</> indexes
!       using constraints. Other indexes can be dropped using <literal>DROP INDEX</>.
       </para>
      </listitem>
  
***************
*** 139,144 **** REINDEX { INDEX | TABLE | DATABASE | SYSTEM } <replaceable class="PARAMETER">nam
--- 151,171 ----
     </varlistentry>
  
     <varlistentry>
+     <term><literal>CONCURRENTLY</literal></term>
+     <listitem>
+      <para>
+       When this option is used, <productname>PostgreSQL</> will rebuild the
+       index without taking any locks that prevent concurrent inserts,
+       updates, or deletes on the table; whereas a standard reindex build
+       locks out writes (but not reads) on the table until it's done.
+       There are several caveats to be aware of when using this option
+       &mdash; see <xref linkend="SQL-REINDEX-CONCURRENTLY"
+       endterm="SQL-REINDEX-CONCURRENTLY-title">.
+      </para>
+     </listitem>
+    </varlistentry>
+ 
+    <varlistentry>
      <term><literal>FORCE</literal></term>
      <listitem>
       <para>
***************
*** 231,236 **** REINDEX { INDEX | TABLE | DATABASE | SYSTEM } <replaceable class="PARAMETER">nam
--- 258,376 ----
     to be reindexed by separate commands.  This is still possible, but
     redundant.
    </para>
+ 
+ 
+   <refsect2 id="SQL-REINDEX-CONCURRENTLY">
+    <title id="SQL-REINDEX-CONCURRENTLY-title">Rebuilding Indexes Concurrently</title>
+ 
+    <indexterm zone="SQL-REINDEX-CONCURRENTLY">
+    <primary>index</primary>
+    <secondary>rebuilding concurrently</secondary>
+    </indexterm>
+ 
+    <para>
+     Rebuilding an index can interfere with regular operation of a database.
+     Normally <productname>PostgreSQL</> locks the table whose index is rebuilt
+     against writes and performs the entire index build with a single scan of the
+     table. Other transactions can still read the table, but if they try to
+     insert, update, or delete rows in the table they will block until the
+     index rebuild is finished. This could have a severe effect if the system is
+     a live production database.  Very large tables can take many hours to be
+     indexed, and even for smaller tables, an index rebuild can lock out writers
+     for periods that are unacceptably long for a production system.
+    </para>
+ 
+    <para>
+     <productname>PostgreSQL</> supports rebuilding indexes without locking
+     out writes.  This method is invoked by specifying the
+     <literal>CONCURRENTLY</> option of <command>REINDEX</>.
+     When this option is used, <productname>PostgreSQL</> must perform two
+     scans of the table for each index that needs to be rebuild and in
+     addition it must wait for all existing transactions that could potentially
+     use the index to terminate. This method requires more total work than a
+     standard index rebuild and takes significantly longer to complete as it
+     needs to wait for unfinished transactions that might modify the index.
+     However, since it allows normal operations to continue while the index
+     is rebuilt, this method is useful for rebuilding indexes in a production
+     environment.  Of course, the extra CPU, memory and I/O load imposed by
+     the index rebuild might slow other operations.
+    </para>
+ 
+    <para>
+     In a concurrent index build, a new index whose storage will replace the one
+     to be rebuild is actually entered into the system catalogs in one transaction,
+     then two table scans occur in two more transactions.  Once this is performed,
+     the old and fresh indexes are swapped in. During this phase the concurrent
+     index is marked as valid, is then swapped and marked as invalid. An exclusive
+     lock is taken at this phase. Finally two additional transactions are used to
+     mark the concurrent index as not ready and then drop it.
+    </para>
+ 
+    <para>
+     If a problem arises while rebuilding the indexes, such as a
+     uniqueness violation in a unique index, the <command>REINDEX</>
+     command will fail but leave behind an <quote>invalid</> new index on top
+     of the existing one. This index will be ignored for querying purposes
+     because it might be incomplete; however it will still consume update
+     overhead. The <application>psql</> <command>\d</> command will report
+     such an index as <literal>INVALID</>:
+ 
+ <programlisting>
+ postgres=# \d tab
+        Table "public.tab"
+  Column |  Type   | Modifiers
+ --------+---------+-----------
+  col    | integer |
+ Indexes:
+     "idx" btree (col)
+     "idx_cct" btree (col) INVALID
+ </programlisting>
+ 
+     The recommended recovery method in such cases is to drop the concurrent
+     index and try again to perform <command>REINDEX CONCURRENTLY</>.
+     The concurrent index created during the processing has a name finishing by
+     the suffix cct. This works as well with indexes of toast relations.
+    </para>
+ 
+    <para>
+     Regular index builds permit other regular index builds on the
+     same table to occur in parallel, but only one concurrent index build
+     can occur on a table at a time.  In both cases, no other types of schema
+     modification on the table are allowed meanwhile.  Another difference
+     is that a regular <command>REINDEX TABLE</> or <command>REINDEX INDEX</>
+     command can be performed within a transaction block, but
+     <command>REINDEX CONCURRENTLY</> cannot. <command>REINDEX DATABASE</> is
+     by default not allowed to run inside a transaction block, so in this case
+     <command>CONCURRENTLY</> is not supported.
+    </para>
+ 
+    <para>
+     Invalid indexes of toast relations can be dropped if a failure occurred
+     during <command>REINDEX CONCURRENTLY</>. Live indexes of toast relations
+     cannot be dropped.
+    </para>
+ 
+    <para>
+     <command>REINDEX DATABASE</command> used with <command>CONCURRENTLY
+     </command> rebuilds concurrently only the non-system relations. System
+     relations are rebuilt with a non-concurrent context. Toast indexes are
+     rebuilt concurrently if the relation they depend on is a non-system
+     relation.
+    </para>
+ 
+    <para>
+     <command>REINDEX</command> uses <literal>ACCESS EXCLUSIVE</literal> lock
+     on all the relations involved during operation. When <command>CONCURRENTLY</command>
+     is specified, the operation is done with <literal>SHARE UPDATE EXCLUSIVE</literal>
+     except during relation swap where <literal>ACCESS EXCLUSIVE</literal> lock
+     is taken.
+    </para>
+ 
+    <para>
+     <command>REINDEX SYSTEM</command> does not support <command>CONCURRENTLY
+     </command>.
+    </para>
+   </refsect2>
   </refsect1>
  
   <refsect1>
***************
*** 262,268 **** $ <userinput>psql broken_db</userinput>
  ...
  broken_db=&gt; REINDEX DATABASE broken_db;
  broken_db=&gt; \q
! </programlisting></para>
   </refsect1>
  
   <refsect1>
--- 402,419 ----
  ...
  broken_db=&gt; REINDEX DATABASE broken_db;
  broken_db=&gt; \q
! </programlisting>
!   </para>
! 
!   <para>
!    Rebuild a table while authorizing read and write operations on involved
!    relations when performed:
! 
! <programlisting>
! REINDEX TABLE CONCURRENTLY my_broken_table;
! </programlisting>
!   </para>
! 
   </refsect1>
  
   <refsect1>
*** a/src/backend/catalog/index.c
--- b/src/backend/catalog/index.c
***************
*** 43,51 ****
--- 43,53 ----
  #include "catalog/pg_trigger.h"
  #include "catalog/pg_type.h"
  #include "catalog/storage.h"
+ #include "commands/defrem.h"
  #include "commands/tablecmds.h"
  #include "commands/trigger.h"
  #include "executor/executor.h"
+ #include "mb/pg_wchar.h"
  #include "miscadmin.h"
  #include "nodes/makefuncs.h"
  #include "nodes/nodeFuncs.h"
***************
*** 672,677 **** UpdateIndexRelation(Oid indexoid,
--- 674,683 ----
   *		will be marked "invalid" and the caller must take additional steps
   *		to fix it up.
   * is_internal: if true, post creation hook for new index
+  * is_reindex: if true, create an index that is used as a duplicate of an
+  *		existing index created during a concurrent operation. This index can
+  *		also be a toast relation. Sufficient locks are normally taken on
+  *		the related relations once this is called during a concurrent operation.
   *
   * Returns the OID of the created index.
   */
***************
*** 695,701 **** index_create(Relation heapRelation,
  			 bool allow_system_table_mods,
  			 bool skip_build,
  			 bool concurrent,
! 			 bool is_internal)
  {
  	Oid			heapRelationId = RelationGetRelid(heapRelation);
  	Relation	pg_class;
--- 701,708 ----
  			 bool allow_system_table_mods,
  			 bool skip_build,
  			 bool concurrent,
! 			 bool is_internal,
! 			 bool is_reindex)
  {
  	Oid			heapRelationId = RelationGetRelid(heapRelation);
  	Relation	pg_class;
***************
*** 738,756 **** index_create(Relation heapRelation,
  
  	/*
  	 * concurrent index build on a system catalog is unsafe because we tend to
! 	 * release locks before committing in catalogs
  	 */
  	if (concurrent &&
! 		IsSystemRelation(heapRelation))
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("concurrent index creation on system catalog tables is not supported")));
  
  	/*
! 	 * This case is currently not supported, but there's no way to ask for it
! 	 * in the grammar anyway, so it can't happen.
  	 */
! 	if (concurrent && is_exclusion)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg_internal("concurrent index creation for exclusion constraints is not supported")));
--- 745,766 ----
  
  	/*
  	 * concurrent index build on a system catalog is unsafe because we tend to
! 	 * release locks before committing in catalogs. If the index is created during
! 	 * a REINDEX CONCURRENTLY operation, sufficient locks are already taken.
  	 */
  	if (concurrent &&
! 		IsSystemRelation(heapRelation) &&
! 		!is_reindex)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("concurrent index creation on system catalog tables is not supported")));
  
  	/*
! 	 * This case is currently only supported during a concurrent index
! 	 * rebuild, but there is no way to ask for it in the grammar otherwise
! 	 * anyway.
  	 */
! 	if (concurrent && is_exclusion && !is_reindex)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg_internal("concurrent index creation for exclusion constraints is not supported")));
***************
*** 1090,1095 **** index_create(Relation heapRelation,
--- 1100,1537 ----
  	return indexRelationId;
  }
  
+ 
+ /*
+  * index_concurrent_create
+  *
+  * Create an index based on the given one that will be used for concurrent
+  * operations. The index is inserted into catalogs and needs to be built later
+  * on. This is called during concurrent index processing. The heap relation
+  * on which is based the index needs to be closed by the caller.
+  */
+ Oid
+ index_concurrent_create(Relation heapRelation, Oid indOid, char *concurrentName)
+ {
+ 	Relation	indexRelation;
+ 	IndexInfo  *indexInfo;
+ 	Oid			concurrentOid = InvalidOid;
+ 	List	   *columnNames = NIL;
+ 	List	   *indexprs = NIL;
+ 	ListCell   *indexpr_item;
+ 	int			i;
+ 	HeapTuple	indexTuple, classTuple;
+ 	Datum		indclassDatum, colOptionDatum, optionDatum;
+ 	oidvector  *indclass;
+ 	int2vector *indcoloptions;
+ 	bool		isnull;
+ 	bool		initdeferred = false;
+ 	Oid			constraintOid = get_index_constraint(indOid);
+ 
+ 	indexRelation = index_open(indOid, RowExclusiveLock);
+ 
+ 	/* Concurrent index uses the same index information as former index */
+ 	indexInfo = BuildIndexInfo(indexRelation);
+ 
+ 	/*
+ 	 * Determine if index is initdeferred, this depends on its dependent
+ 	 * constraint.
+ 	 */
+ 	if (OidIsValid(constraintOid))
+ 	{
+ 		/* Look for the correct value */
+ 		HeapTuple			constraintTuple;
+ 		Form_pg_constraint	constraintForm;
+ 
+ 		constraintTuple = SearchSysCache1(CONSTROID,
+ 									 ObjectIdGetDatum(constraintOid));
+ 		if (!HeapTupleIsValid(constraintTuple))
+ 			elog(ERROR, "cache lookup failed for constraint %u",
+ 				 constraintOid);
+ 		constraintForm = (Form_pg_constraint) GETSTRUCT(constraintTuple);
+ 		initdeferred = constraintForm->condeferred;
+ 
+ 		ReleaseSysCache(constraintTuple);
+ 	}
+ 
+ 	/* Get expressions associated to this index for compilation of column names */
+ 	indexprs = RelationGetIndexExpressions(indexRelation);
+ 	indexpr_item = list_head(indexprs);
+ 
+ 	/* Build the list of column names, necessary for index_create */
+ 	for (i = 0; i < indexInfo->ii_NumIndexAttrs; i++)
+ 	{
+ 		char	   *origname, *curname;
+ 		char		buf[NAMEDATALEN];
+ 		AttrNumber	attnum = indexInfo->ii_KeyAttrNumbers[i];
+ 		int			j;
+ 
+ 		/* Pick up column name depending on attribute type */
+ 		if (attnum > 0)
+ 		{
+ 			/*
+ 			 * This is a column attribute, so simply pick column name from
+ 			 * relation.
+ 			 */
+ 			Form_pg_attribute attform = heapRelation->rd_att->attrs[attnum - 1];;
+ 			origname = pstrdup(NameStr(attform->attname));
+ 		}
+ 		else if (attnum < 0)
+ 		{
+ 			/* Case of a system attribute */
+ 			Form_pg_attribute attform = SystemAttributeDefinition(attnum,
+ 										  heapRelation->rd_rel->relhasoids);
+ 			origname = pstrdup(NameStr(attform->attname));
+ 		}
+ 		else
+ 		{
+ 			Node *indnode;
+ 			/*
+ 			 * This is the case of an expression, so pick up the expression
+ 			 * name.
+ 			 */
+ 			Assert(indexpr_item != NULL);
+ 			indnode = (Node *) lfirst(indexpr_item);
+ 			indexpr_item = lnext(indexpr_item);
+ 			origname = deparse_expression(indnode,
+ 							deparse_context_for(RelationGetRelationName(heapRelation),
+ 												RelationGetRelid(heapRelation)),
+ 							false, false);
+ 		}
+ 
+ 		/*
+ 		 * Check if the name picked has any conflict with existing names and
+ 		 * change it.
+ 		 */
+ 		curname = origname;
+ 		for (j = 1;; j++)
+ 		{
+ 			ListCell   *lc2;
+ 			char		nbuf[32];
+ 			int			nlen;
+ 
+ 			foreach(lc2, columnNames)
+ 			{
+ 				if (strcmp(curname, (char *) lfirst(lc2)) == 0)
+ 					break;
+ 			}
+ 			if (lc2 == NULL)
+ 				break; /* found nonconflicting name */
+ 
+ 			sprintf(nbuf, "%d", j);
+ 
+ 			/* Ensure generated names are shorter than NAMEDATALEN */
+ 			nlen = pg_mbcliplen(origname, strlen(origname),
+ 								NAMEDATALEN - 1 - strlen(nbuf));
+ 			memcpy(buf, origname, nlen);
+ 			strcpy(buf + nlen, nbuf);
+ 			curname = buf;
+ 		}
+ 
+ 		/* Append name to existing list */
+ 		columnNames = lappend(columnNames, pstrdup(curname));
+ 	}
+ 
+ 	/* Get the array of class and column options IDs from index info */
+ 	indexTuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(indOid));
+ 	if (!HeapTupleIsValid(indexTuple))
+ 		elog(ERROR, "cache lookup failed for index %u", indOid);
+ 	indclassDatum = SysCacheGetAttr(INDEXRELID, indexTuple,
+ 									Anum_pg_index_indclass, &isnull);
+ 	Assert(!isnull);
+ 	indclass = (oidvector *) DatumGetPointer(indclassDatum);
+ 
+ 	colOptionDatum = SysCacheGetAttr(INDEXRELID, indexTuple,
+ 									 Anum_pg_index_indoption, &isnull);
+ 	Assert(!isnull);
+ 	indcoloptions = (int2vector *) DatumGetPointer(colOptionDatum);
+ 
+ 	/* Fetch options of index if any */
+ 	classTuple = SearchSysCache1(RELOID, indOid);
+ 	if (!HeapTupleIsValid(classTuple))
+ 		elog(ERROR, "cache lookup failed for relation %u", indOid);
+ 	optionDatum = SysCacheGetAttr(RELOID, classTuple,
+ 								  Anum_pg_class_reloptions, &isnull);
+ 
+ 	/* Now create the concurrent index */
+ 	concurrentOid = index_create(heapRelation,
+ 								 (const char *) concurrentName,
+ 								 InvalidOid,
+ 								 InvalidOid,
+ 								 indexInfo,
+ 								 columnNames,
+ 								 indexRelation->rd_rel->relam,
+ 								 indexRelation->rd_rel->reltablespace,
+ 								 indexRelation->rd_indcollation,
+ 								 indclass->values,
+ 								 indcoloptions->values,
+ 								 optionDatum,
+ 								 indexRelation->rd_index->indisprimary,
+ 								 OidIsValid(constraintOid),	/* is constraint? */
+ 								 !indexRelation->rd_index->indimmediate,	/* is deferrable? */
+ 								 initdeferred,	/* is initially deferred? */
+ 								 true,	/* allow table to be a system catalog? */
+ 								 true,	/* skip build? */
+ 								 true,	/* concurrent? */
+ 								 false,	/* is_internal */
+ 								 true); /* reindex? */
+ 
+ 	/* Close the relations used and clean up */
+ 	index_close(indexRelation, NoLock);
+ 	ReleaseSysCache(indexTuple);
+ 	ReleaseSysCache(classTuple);
+ 
+ 	return concurrentOid;
+ }
+ 
+ 
+ /*
+  * index_concurrent_build
+  *
+  * Build index for a concurrent operation. Low-level locks are taken when this
+  * operation is performed to prevent only schema changes.
+  */
+ void
+ index_concurrent_build(Oid heapOid,
+ 					   Oid indexOid,
+ 					   bool isprimary)
+ {
+ 	Relation	rel,
+ 				indexRelation;
+ 	IndexInfo  *indexInfo;
+ 
+ 	/* Open and lock the parent heap relation */
+ 	rel = heap_open(heapOid, ShareUpdateExclusiveLock);
+ 
+ 	/* And the target index relation */
+ 	indexRelation = index_open(indexOid, RowExclusiveLock);
+ 
+ 	/*
+ 	 * We have to re-build the IndexInfo struct, since it was lost in
+ 	 * commit of transaction where this concurrent index was created
+ 	 * at the catalog level.
+ 	 */
+ 	indexInfo = BuildIndexInfo(indexRelation);
+ 	Assert(!indexInfo->ii_ReadyForInserts);
+ 	indexInfo->ii_Concurrent = true;
+ 	indexInfo->ii_BrokenHotChain = false;
+ 
+ 	/* Now build the index */
+ 	index_build(rel, indexRelation, indexInfo, isprimary, false);
+ 
+ 	/* Close both the relations, but keep the locks */
+ 	heap_close(rel, NoLock);
+ 	index_close(indexRelation, NoLock);
+ }
+ 
+ 
+ /*
+  * index_concurrent_swap
+  *
+  * Swap old index and new index in a concurrent context. For the time being
+  * what is done here is switching the relation relfilenode of the indexes. If
+  * extra operations are necessary during a concurrent swap, processing should
+  * be added here. AccessExclusiveLock is taken on the index relations that are
+  * swapped until the end of the transaction where this function is called.
+  * Note: a lower lock could be taken if catalog cache with SnapshotNow was
+  * correctly MVCC'd.
+  */
+ void
+ index_concurrent_swap(Oid newIndexOid, Oid oldIndexOid)
+ {
+ 	Relation		oldIndexRel, newIndexRel, pg_class;
+ 	HeapTuple		oldIndexTuple, newIndexTuple;
+ 	Form_pg_class	oldIndexForm, newIndexForm;
+ 	Oid				tmpnode;
+ 
+ 	/*
+ 	 * Take an exclusive lock on the old and new index before swapping them.
+ 	 */
+ 	oldIndexRel = relation_open(oldIndexOid, AccessExclusiveLock);
+ 	newIndexRel = relation_open(newIndexOid, AccessExclusiveLock);
+ 
+ 	/* Now swap relfilenode of those indexes */
+ 	pg_class = heap_open(RelationRelationId, RowExclusiveLock);
+ 
+ 	oldIndexTuple = SearchSysCacheCopy1(RELOID,
+ 										ObjectIdGetDatum(oldIndexOid));
+ 	if (!HeapTupleIsValid(oldIndexTuple))
+ 		elog(ERROR, "could not find tuple for relation %u", oldIndexOid);
+ 	newIndexTuple = SearchSysCacheCopy1(RELOID,
+ 										ObjectIdGetDatum(newIndexOid));
+ 	if (!HeapTupleIsValid(newIndexTuple))
+ 		elog(ERROR, "could not find tuple for relation %u", newIndexOid);
+ 	oldIndexForm = (Form_pg_class) GETSTRUCT(oldIndexTuple);
+ 	newIndexForm = (Form_pg_class) GETSTRUCT(newIndexTuple);
+ 
+ 	/* Here is where the actual swapping happens */
+ 	tmpnode = oldIndexForm->relfilenode;
+ 	oldIndexForm->relfilenode = newIndexForm->relfilenode;
+ 	newIndexForm->relfilenode = tmpnode;
+ 
+ 	/* Then update the tuples for each relation */
+ 	simple_heap_update(pg_class, &oldIndexTuple->t_self, oldIndexTuple);
+ 	simple_heap_update(pg_class, &newIndexTuple->t_self, newIndexTuple);
+ 	CatalogUpdateIndexes(pg_class, oldIndexTuple);
+ 	CatalogUpdateIndexes(pg_class, newIndexTuple);
+ 
+ 	/* Close relations and clean up */
+ 	heap_freetuple(oldIndexTuple);
+ 	heap_freetuple(newIndexTuple);
+ 	heap_close(pg_class, RowExclusiveLock);
+ 
+ 	/* The lock taken previously is not released until the end of transaction */
+ 	relation_close(oldIndexRel, NoLock);
+ 	relation_close(newIndexRel, NoLock);
+ }
+ 
+ /*
+  * index_concurrent_set_dead
+  *
+  * Perform the last invalidation stage of DROP INDEX CONCURRENTLY before
+  * actually dropping the index. After calling this function the index is
+  * seen by all the backends as dead.
+  */
+ void
+ index_concurrent_set_dead(Oid indexId, Oid heapId, LOCKTAG locktag)
+ {
+ 	Relation	heapRelation;
+ 	Relation	indexRelation;
+ 
+ 	/*
+ 	 * Now we must wait until no running transaction could be using the
+ 	 * index for a query if necessary.
+ 	 *
+ 	 * Note: the reason we use actual lock acquisition here, rather than
+ 	 * just checking the ProcArray and sleeping, is that deadlock is
+ 	 * possible if one of the transactions in question is blocked trying
+ 	 * to acquire an exclusive lock on our table. The lock code will
+ 	 * detect deadlock and error out properly.
+ 	 */
+ 	WaitForVirtualLocks(locktag, AccessExclusiveLock);
+ 
+ 	/*
+ 	 * No more predicate locks will be acquired on this index, and we're
+ 	 * about to stop doing inserts into the index which could show
+ 	 * conflicts with existing predicate locks, so now is the time to move
+ 	 * them to the heap relation.
+ 	 */
+ 	heapRelation = heap_open(heapId, ShareUpdateExclusiveLock);
+ 	indexRelation = index_open(indexId, ShareUpdateExclusiveLock);
+ 	TransferPredicateLocksToHeapRelation(indexRelation);
+ 
+ 	/*
+ 	 * Now we are sure that nobody uses the index for queries; they just
+ 	 * might have it open for updating it.	So now we can unset indisready
+ 	 * and indislive, then wait till nobody could be using it at all
+ 	 * anymore.
+ 	 */
+ 	index_set_state_flags(indexId, INDEX_DROP_SET_DEAD, true);
+ 
+ 	/*
+ 	 * Invalidate the relcache for the table, so that after this commit
+ 	 * all sessions will refresh the table's index list.  Forgetting just
+ 	 * the index's relcache entry is not enough.
+ 	 */
+ 	CacheInvalidateRelcache(heapRelation);
+ 
+ 	/*
+ 	 * Close the relations again, though still holding session lock.
+ 	 */
+ 	heap_close(heapRelation, NoLock);
+ 	index_close(indexRelation, NoLock);
+ }
+ 
+ /*
+  * index_concurrent_clear_valid
+  *
+  * Release the valid state of a given index and then release the cache of
+  * its parent relation. This function should be called when initializing an
+  * index drop in a concurrent context before setting the index as dead if
+  * if called in a concurrent context.
+  */
+ void
+ index_concurrent_clear_valid(Relation heapRelation,
+ 							 Oid indexOid,
+ 							 bool concurrent)
+ {
+ 	/*
+ 	 * Mark index invalid by updating its pg_index entry
+ 	 */
+ 	index_set_state_flags(indexOid, INDEX_DROP_CLEAR_VALID, concurrent);
+ 
+ 	/*
+ 	 * Invalidate the relcache for the table, so that after this commit
+ 	 * all sessions will refresh any cached plans that might reference the
+ 	 * index.
+ 	 */
+ 	CacheInvalidateRelcache(heapRelation);
+ }
+ 
+ /*
+  * index_concurrent_drop
+  *
+  * Drop a single index concurrently as the last step of an index concurrent
+  * process. Deletion is done through performDeletion or dependencies of the
+  * index would not get dropped. At this point all the indexes are already
+  * considered as invalid and dead so they can be dropped without using any
+  * concurrent options as it is sure that they will not interact with other
+  * server sessions.
+  */
+ void
+ index_concurrent_drop(Oid indexOid)
+ {
+ 	Oid				constraintOid = get_index_constraint(indexOid);
+ 	ObjectAddress	object;
+ 	Form_pg_index	indexForm;
+ 	Relation		pg_index;
+ 	HeapTuple		indexTuple;
+ 
+ 	/*
+ 	 * Check that the index dropped here is not alive, it might be used by
+ 	 * other backends in this case.
+ 	 */
+ 	pg_index = heap_open(IndexRelationId, RowExclusiveLock);
+ 
+ 	indexTuple = SearchSysCacheCopy1(INDEXRELID,
+ 									 ObjectIdGetDatum(indexOid));
+ 	if (!HeapTupleIsValid(indexTuple))
+ 		elog(ERROR, "cache lookup failed for index %u", indexOid);
+ 	indexForm = (Form_pg_index) GETSTRUCT(indexTuple);
+ 
+ 	/*
+ 	 * This is only a safety check, just to avoid live indexes from being
+ 	 * dropped.
+ 	 */
+ 	if (indexForm->indislive)
+ 		elog(ERROR, "cannot drop live index with OID %u", indexOid);
+ 
+ 	/* Clean up */
+ 	heap_close(pg_index, RowExclusiveLock);
+ 
+ 	/*
+ 	 * We are sure to have a dead index, so begin the drop process.
+ 	 * Register constraint or index for drop.
+ 	 */
+ 	if (OidIsValid(constraintOid))
+ 	{
+ 		object.classId = ConstraintRelationId;
+ 		object.objectId = constraintOid;
+ 	}
+ 	else
+ 	{
+ 		object.classId = RelationRelationId;
+ 		object.objectId = indexOid;
+ 	}
+ 
+ 	object.objectSubId = 0;
+ 
+ 	/* Perform deletion for normal and toast indexes */
+ 	performDeletion(&object,
+ 					DROP_RESTRICT,
+ 					0);
+ }
+ 
+ 
  /*
   * index_constraint_create
   *
***************
*** 1325,1331 **** index_drop(Oid indexId, bool concurrent)
  				indexrelid;
  	LOCKTAG		heaplocktag;
  	LOCKMODE	lockmode;
- 	VirtualTransactionId *old_lockholders;
  
  	/*
  	 * To drop an index safely, we must grab exclusive lock on its parent
--- 1767,1772 ----
***************
*** 1407,1423 **** index_drop(Oid indexId, bool concurrent)
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("DROP INDEX CONCURRENTLY must be first action in transaction")));
  
! 		/*
! 		 * Mark index invalid by updating its pg_index entry
! 		 */
! 		index_set_state_flags(indexId, INDEX_DROP_CLEAR_VALID);
! 
! 		/*
! 		 * Invalidate the relcache for the table, so that after this commit
! 		 * all sessions will refresh any cached plans that might reference the
! 		 * index.
! 		 */
! 		CacheInvalidateRelcache(userHeapRelation);
  
  		/* save lockrelid and locktag for below, then close but keep locks */
  		heaprelid = userHeapRelation->rd_lockInfo.lockRelId;
--- 1848,1855 ----
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("DROP INDEX CONCURRENTLY must be first action in transaction")));
  
! 		/* Mark the index as invalid */
! 		index_concurrent_clear_valid(userHeapRelation, indexId, true);
  
  		/* save lockrelid and locktag for below, then close but keep locks */
  		heaprelid = userHeapRelation->rd_lockInfo.lockRelId;
***************
*** 1445,1507 **** index_drop(Oid indexId, bool concurrent)
  		CommitTransactionCommand();
  		StartTransactionCommand();
  
! 		/*
! 		 * Now we must wait until no running transaction could be using the
! 		 * index for a query.  To do this, inquire which xacts currently would
! 		 * conflict with AccessExclusiveLock on the table -- ie, which ones
! 		 * have a lock of any kind on the table. Then wait for each of these
! 		 * xacts to commit or abort. Note we do not need to worry about xacts
! 		 * that open the table for reading after this point; they will see the
! 		 * index as invalid when they open the relation.
! 		 *
! 		 * Note: the reason we use actual lock acquisition here, rather than
! 		 * just checking the ProcArray and sleeping, is that deadlock is
! 		 * possible if one of the transactions in question is blocked trying
! 		 * to acquire an exclusive lock on our table.  The lock code will
! 		 * detect deadlock and error out properly.
! 		 *
! 		 * Note: GetLockConflicts() never reports our own xid, hence we need
! 		 * not check for that.	Also, prepared xacts are not reported, which
! 		 * is fine since they certainly aren't going to do anything more.
! 		 */
! 		old_lockholders = GetLockConflicts(&heaplocktag, AccessExclusiveLock);
! 
! 		while (VirtualTransactionIdIsValid(*old_lockholders))
! 		{
! 			VirtualXactLock(*old_lockholders, true);
! 			old_lockholders++;
! 		}
! 
! 		/*
! 		 * No more predicate locks will be acquired on this index, and we're
! 		 * about to stop doing inserts into the index which could show
! 		 * conflicts with existing predicate locks, so now is the time to move
! 		 * them to the heap relation.
! 		 */
! 		userHeapRelation = heap_open(heapId, ShareUpdateExclusiveLock);
! 		userIndexRelation = index_open(indexId, ShareUpdateExclusiveLock);
! 		TransferPredicateLocksToHeapRelation(userIndexRelation);
! 
! 		/*
! 		 * Now we are sure that nobody uses the index for queries; they just
! 		 * might have it open for updating it.	So now we can unset indisready
! 		 * and indislive, then wait till nobody could be using it at all
! 		 * anymore.
! 		 */
! 		index_set_state_flags(indexId, INDEX_DROP_SET_DEAD);
! 
! 		/*
! 		 * Invalidate the relcache for the table, so that after this commit
! 		 * all sessions will refresh the table's index list.  Forgetting just
! 		 * the index's relcache entry is not enough.
! 		 */
! 		CacheInvalidateRelcache(userHeapRelation);
! 
! 		/*
! 		 * Close the relations again, though still holding session lock.
! 		 */
! 		heap_close(userHeapRelation, NoLock);
! 		index_close(userIndexRelation, NoLock);
  
  		/*
  		 * Again, commit the transaction to make the pg_index update visible
--- 1877,1884 ----
  		CommitTransactionCommand();
  		StartTransactionCommand();
  
! 		/* Finish invalidation of index and mark it as dead */
! 		index_concurrent_set_dead(indexId, heapId, heaplocktag);
  
  		/*
  		 * Again, commit the transaction to make the pg_index update visible
***************
*** 1514,1526 **** index_drop(Oid indexId, bool concurrent)
  		 * Wait till every transaction that saw the old index state has
  		 * finished.  The logic here is the same as above.
  		 */
! 		old_lockholders = GetLockConflicts(&heaplocktag, AccessExclusiveLock);
! 
! 		while (VirtualTransactionIdIsValid(*old_lockholders))
! 		{
! 			VirtualXactLock(*old_lockholders, true);
! 			old_lockholders++;
! 		}
  
  		/*
  		 * Re-open relations to allow us to complete our actions.
--- 1891,1897 ----
  		 * Wait till every transaction that saw the old index state has
  		 * finished.  The logic here is the same as above.
  		 */
! 		WaitForVirtualLocks(heaplocktag, AccessExclusiveLock);
  
  		/*
  		 * Re-open relations to allow us to complete our actions.
***************
*** 2991,3017 **** validate_index_heapscan(Relation heapRelation,
   * index_set_state_flags - adjust pg_index state flags
   *
   * This is used during CREATE/DROP INDEX CONCURRENTLY to adjust the pg_index
!  * flags that denote the index's state.  We must use an in-place update of
!  * the pg_index tuple, because we do not have exclusive lock on the parent
!  * table and so other sessions might concurrently be doing SnapshotNow scans
!  * of pg_index to identify the table's indexes.  A transactional update would
!  * risk somebody not seeing the index at all.  Because the update is not
!  * transactional and will not roll back on error, this must only be used as
!  * the last step in a transaction that has not made any transactional catalog
!  * updates!
   *
   * Note that heap_inplace_update does send a cache inval message for the
   * tuple, so other sessions will hear about the update as soon as we commit.
   */
  void
! index_set_state_flags(Oid indexId, IndexStateFlagsAction action)
  {
  	Relation	pg_index;
  	HeapTuple	indexTuple;
  	Form_pg_index indexForm;
  
! 	/* Assert that current xact hasn't done any transactional updates */
! 	Assert(GetTopTransactionIdIfAny() == InvalidTransactionId);
  
  	/* Open pg_index and fetch a writable copy of the index's tuple */
  	pg_index = heap_open(IndexRelationId, RowExclusiveLock);
--- 3362,3393 ----
   * index_set_state_flags - adjust pg_index state flags
   *
   * This is used during CREATE/DROP INDEX CONCURRENTLY to adjust the pg_index
!  * flags that denote the index's state.  If this function is called in a
!  * concurrent process, we use an in-place update of the pg_index tuple,
!  * because we do not have exclusive lock on the parent table and so other
!  * sessions might concurrently be doing SnapshotNow scans of pg_index to
!  * identify the table's indexes.  A transactional update would risk somebody
!  * not seeing the index at all.  Because the update is not transactional
!  * and will not roll back on error, this must only be used as the last step
!  * in a transaction that has not made any transactional catalog updates!
   *
   * Note that heap_inplace_update does send a cache inval message for the
   * tuple, so other sessions will hear about the update as soon as we commit.
   */
  void
! index_set_state_flags(Oid indexId,
! 					  IndexStateFlagsAction action,
! 					  bool concurrent)
  {
  	Relation	pg_index;
  	HeapTuple	indexTuple;
  	Form_pg_index indexForm;
  
! 	/*
! 	 * Assert that current xact hasn't done any transactional updates, there
! 	 * is nothing to worry in a non-concurrent context.
! 	 */
! 	Assert(!concurrent || GetTopTransactionIdIfAny() == InvalidTransactionId);
  
  	/* Open pg_index and fetch a writable copy of the index's tuple */
  	pg_index = heap_open(IndexRelationId, RowExclusiveLock);
***************
*** 3071,3078 **** index_set_state_flags(Oid indexId, IndexStateFlagsAction action)
  			break;
  	}
  
! 	/* ... and write it back in-place */
! 	heap_inplace_update(pg_index, indexTuple);
  
  	heap_close(pg_index, RowExclusiveLock);
  }
--- 3447,3466 ----
  			break;
  	}
  
! 	/*
! 	 * Write it back in-place in a concurrent context, and do a simple update
! 	 * for a non-concurrent context.
! 	 */
! 	if (concurrent)
! 	{
! 		heap_inplace_update(pg_index, indexTuple);
! 	}
! 	else
! 	{
! 		simple_heap_update(pg_index, &indexTuple->t_self, indexTuple);
! 		CommandCounterIncrement();
! 		CatalogUpdateIndexes(pg_index, indexTuple);
! 	}
  
  	heap_close(pg_index, RowExclusiveLock);
  }
*** a/src/backend/catalog/toasting.c
--- b/src/backend/catalog/toasting.c
***************
*** 281,287 **** create_toast_table(Relation rel, Oid toastOid, Oid toastIndexOid, Datum reloptio
  				 rel->rd_rel->reltablespace,
  				 collationObjectId, classObjectId, coloptions, (Datum) 0,
  				 true, false, false, false,
! 				 true, false, false, true);
  
  	heap_close(toast_rel, NoLock);
  
--- 281,287 ----
  				 rel->rd_rel->reltablespace,
  				 collationObjectId, classObjectId, coloptions, (Datum) 0,
  				 true, false, false, false,
! 				 true, false, false, false, false);
  
  	heap_close(toast_rel, NoLock);
  
*** a/src/backend/commands/indexcmds.c
--- b/src/backend/commands/indexcmds.c
***************
*** 68,75 **** static void ComputeIndexAttrs(IndexInfo *indexInfo,
  static Oid GetIndexOpClass(List *opclass, Oid attrType,
  				char *accessMethodName, Oid accessMethodId);
  static char *ChooseIndexName(const char *tabname, Oid namespaceId,
! 				List *colnames, List *exclusionOpNames,
! 				bool primary, bool isconstraint);
  static char *ChooseIndexNameAddition(List *colnames);
  static List *ChooseIndexColumnNames(List *indexElems);
  static void RangeVarCallbackForReindexIndex(const RangeVar *relation,
--- 68,76 ----
  static Oid GetIndexOpClass(List *opclass, Oid attrType,
  				char *accessMethodName, Oid accessMethodId);
  static char *ChooseIndexName(const char *tabname, Oid namespaceId,
! 							 List *colnames, List *exclusionOpNames,
! 							 bool primary, bool isconstraint,
! 							 bool concurrent);
  static char *ChooseIndexNameAddition(List *colnames);
  static List *ChooseIndexColumnNames(List *indexElems);
  static void RangeVarCallbackForReindexIndex(const RangeVar *relation,
***************
*** 311,317 **** DefineIndex(IndexStmt *stmt,
  	Oid			tablespaceId;
  	List	   *indexColNames;
  	Relation	rel;
- 	Relation	indexRelation;
  	HeapTuple	tuple;
  	Form_pg_am	accessMethodForm;
  	bool		amcanorder;
--- 312,317 ----
***************
*** 321,333 **** DefineIndex(IndexStmt *stmt,
  	IndexInfo  *indexInfo;
  	int			numberOfAttributes;
  	TransactionId limitXmin;
- 	VirtualTransactionId *old_lockholders;
- 	VirtualTransactionId *old_snapshots;
- 	int			n_old_snapshots;
  	LockRelId	heaprelid;
  	LOCKTAG		heaplocktag;
  	Snapshot	snapshot;
- 	int			i;
  
  	/*
  	 * count attributes in index
--- 321,329 ----
***************
*** 454,460 **** DefineIndex(IndexStmt *stmt,
  											indexColNames,
  											stmt->excludeOpNames,
  											stmt->primary,
! 											stmt->isconstraint);
  
  	/*
  	 * look up the access method, verify it can handle the requested features
--- 450,457 ----
  											indexColNames,
  											stmt->excludeOpNames,
  											stmt->primary,
! 											stmt->isconstraint,
! 											false);
  
  	/*
  	 * look up the access method, verify it can handle the requested features
***************
*** 601,607 **** DefineIndex(IndexStmt *stmt,
  					 stmt->isconstraint, stmt->deferrable, stmt->initdeferred,
  					 allowSystemTableMods,
  					 skip_build || stmt->concurrent,
! 					 stmt->concurrent, !check_rights);
  
  	/* Add any requested comment */
  	if (stmt->idxcomment != NULL)
--- 598,604 ----
  					 stmt->isconstraint, stmt->deferrable, stmt->initdeferred,
  					 allowSystemTableMods,
  					 skip_build || stmt->concurrent,
! 					 stmt->concurrent, !check_rights, false);
  
  	/* Add any requested comment */
  	if (stmt->idxcomment != NULL)
***************
*** 664,681 **** DefineIndex(IndexStmt *stmt,
  	 * one of the transactions in question is blocked trying to acquire an
  	 * exclusive lock on our table.  The lock code will detect deadlock and
  	 * error out properly.
- 	 *
- 	 * Note: GetLockConflicts() never reports our own xid, hence we need not
- 	 * check for that.	Also, prepared xacts are not reported, which is fine
- 	 * since they certainly aren't going to do anything more.
  	 */
! 	old_lockholders = GetLockConflicts(&heaplocktag, ShareLock);
! 
! 	while (VirtualTransactionIdIsValid(*old_lockholders))
! 	{
! 		VirtualXactLock(*old_lockholders, true);
! 		old_lockholders++;
! 	}
  
  	/*
  	 * At this moment we are sure that there are no transactions with the
--- 661,668 ----
  	 * one of the transactions in question is blocked trying to acquire an
  	 * exclusive lock on our table.  The lock code will detect deadlock and
  	 * error out properly.
  	 */
! 	WaitForVirtualLocks(heaplocktag, ShareLock);
  
  	/*
  	 * At this moment we are sure that there are no transactions with the
***************
*** 695,728 **** DefineIndex(IndexStmt *stmt,
  	 * HOT-chain or the extension of the chain is HOT-safe for this index.
  	 */
  
- 	/* Open and lock the parent heap relation */
- 	rel = heap_openrv(stmt->relation, ShareUpdateExclusiveLock);
- 
- 	/* And the target index relation */
- 	indexRelation = index_open(indexRelationId, RowExclusiveLock);
- 
  	/* Set ActiveSnapshot since functions in the indexes may need it */
  	PushActiveSnapshot(GetTransactionSnapshot());
  
! 	/* We have to re-build the IndexInfo struct, since it was lost in commit */
! 	indexInfo = BuildIndexInfo(indexRelation);
! 	Assert(!indexInfo->ii_ReadyForInserts);
! 	indexInfo->ii_Concurrent = true;
! 	indexInfo->ii_BrokenHotChain = false;
! 
! 	/* Now build the index */
! 	index_build(rel, indexRelation, indexInfo, stmt->primary, false);
! 
! 	/* Close both the relations, but keep the locks */
! 	heap_close(rel, NoLock);
! 	index_close(indexRelation, NoLock);
  
  	/*
  	 * Update the pg_index row to mark the index as ready for inserts. Once we
  	 * commit this transaction, any new transactions that open the table must
  	 * insert new entries into the index for insertions and non-HOT updates.
  	 */
! 	index_set_state_flags(indexRelationId, INDEX_CREATE_SET_READY);
  
  	/* we can do away with our snapshot */
  	PopActiveSnapshot();
--- 682,701 ----
  	 * HOT-chain or the extension of the chain is HOT-safe for this index.
  	 */
  
  	/* Set ActiveSnapshot since functions in the indexes may need it */
  	PushActiveSnapshot(GetTransactionSnapshot());
  
! 	/* Perform concurrent build of index */
! 	index_concurrent_build(RangeVarGetRelid(stmt->relation, NoLock, false),
! 						   indexRelationId,
! 						   stmt->primary);
  
  	/*
  	 * Update the pg_index row to mark the index as ready for inserts. Once we
  	 * commit this transaction, any new transactions that open the table must
  	 * insert new entries into the index for insertions and non-HOT updates.
  	 */
! 	index_set_state_flags(indexRelationId, INDEX_CREATE_SET_READY, true);
  
  	/* we can do away with our snapshot */
  	PopActiveSnapshot();
***************
*** 739,751 **** DefineIndex(IndexStmt *stmt,
  	 * We once again wait until no transaction can have the table open with
  	 * the index marked as read-only for updates.
  	 */
! 	old_lockholders = GetLockConflicts(&heaplocktag, ShareLock);
! 
! 	while (VirtualTransactionIdIsValid(*old_lockholders))
! 	{
! 		VirtualXactLock(*old_lockholders, true);
! 		old_lockholders++;
! 	}
  
  	/*
  	 * Now take the "reference snapshot" that will be used by validate_index()
--- 712,718 ----
  	 * We once again wait until no transaction can have the table open with
  	 * the index marked as read-only for updates.
  	 */
! 	WaitForVirtualLocks(heaplocktag, ShareLock);
  
  	/*
  	 * Now take the "reference snapshot" that will be used by validate_index()
***************
*** 786,864 **** DefineIndex(IndexStmt *stmt,
  	 * The index is now valid in the sense that it contains all currently
  	 * interesting tuples.	But since it might not contain tuples deleted just
  	 * before the reference snap was taken, we have to wait out any
! 	 * transactions that might have older snapshots.  Obtain a list of VXIDs
! 	 * of such transactions, and wait for them individually.
! 	 *
! 	 * We can exclude any running transactions that have xmin > the xmin of
! 	 * our reference snapshot; their oldest snapshot must be newer than ours.
! 	 * We can also exclude any transactions that have xmin = zero, since they
! 	 * evidently have no live snapshot at all (and any one they might be in
! 	 * process of taking is certainly newer than ours).  Transactions in other
! 	 * DBs can be ignored too, since they'll never even be able to see this
! 	 * index.
! 	 *
! 	 * We can also exclude autovacuum processes and processes running manual
! 	 * lazy VACUUMs, because they won't be fazed by missing index entries
! 	 * either.	(Manual ANALYZEs, however, can't be excluded because they
! 	 * might be within transactions that are going to do arbitrary operations
! 	 * later.)
! 	 *
! 	 * Also, GetCurrentVirtualXIDs never reports our own vxid, so we need not
! 	 * check for that.
! 	 *
! 	 * If a process goes idle-in-transaction with xmin zero, we do not need to
! 	 * wait for it anymore, per the above argument.  We do not have the
! 	 * infrastructure right now to stop waiting if that happens, but we can at
! 	 * least avoid the folly of waiting when it is idle at the time we would
! 	 * begin to wait.  We do this by repeatedly rechecking the output of
! 	 * GetCurrentVirtualXIDs.  If, during any iteration, a particular vxid
! 	 * doesn't show up in the output, we know we can forget about it.
  	 */
! 	old_snapshots = GetCurrentVirtualXIDs(limitXmin, true, false,
! 										  PROC_IS_AUTOVACUUM | PROC_IN_VACUUM,
! 										  &n_old_snapshots);
! 
! 	for (i = 0; i < n_old_snapshots; i++)
! 	{
! 		if (!VirtualTransactionIdIsValid(old_snapshots[i]))
! 			continue;			/* found uninteresting in previous cycle */
! 
! 		if (i > 0)
! 		{
! 			/* see if anything's changed ... */
! 			VirtualTransactionId *newer_snapshots;
! 			int			n_newer_snapshots;
! 			int			j;
! 			int			k;
! 
! 			newer_snapshots = GetCurrentVirtualXIDs(limitXmin,
! 													true, false,
! 										 PROC_IS_AUTOVACUUM | PROC_IN_VACUUM,
! 													&n_newer_snapshots);
! 			for (j = i; j < n_old_snapshots; j++)
! 			{
! 				if (!VirtualTransactionIdIsValid(old_snapshots[j]))
! 					continue;	/* found uninteresting in previous cycle */
! 				for (k = 0; k < n_newer_snapshots; k++)
! 				{
! 					if (VirtualTransactionIdEquals(old_snapshots[j],
! 												   newer_snapshots[k]))
! 						break;
! 				}
! 				if (k >= n_newer_snapshots)		/* not there anymore */
! 					SetInvalidVirtualTransactionId(old_snapshots[j]);
! 			}
! 			pfree(newer_snapshots);
! 		}
! 
! 		if (VirtualTransactionIdIsValid(old_snapshots[i]))
! 			VirtualXactLock(old_snapshots[i], true);
! 	}
  
  	/*
  	 * Index can now be marked valid -- update its pg_index entry
  	 */
! 	index_set_state_flags(indexRelationId, INDEX_CREATE_SET_VALID);
  
  	/*
  	 * The pg_index update will cause backends (including this one) to update
--- 753,766 ----
  	 * The index is now valid in the sense that it contains all currently
  	 * interesting tuples.	But since it might not contain tuples deleted just
  	 * before the reference snap was taken, we have to wait out any
! 	 * transactions that might have older snapshots.
  	 */
! 	WaitForOldSnapshots(limitXmin);
  
  	/*
  	 * Index can now be marked valid -- update its pg_index entry
  	 */
! 	index_set_state_flags(indexRelationId, INDEX_CREATE_SET_VALID, true);
  
  	/*
  	 * The pg_index update will cause backends (including this one) to update
***************
*** 880,885 **** DefineIndex(IndexStmt *stmt,
--- 782,1331 ----
  
  
  /*
+  * ReindexRelationConcurrently
+  *
+  * Process REINDEX CONCURRENTLY for given relation Oid. The relation can be
+  * either an index or a table. If a table is specified, each reindexing step
+  * is done in parallel with all the table's indexes as well as its dependent
+  * toast indexes.
+  */
+ bool
+ ReindexRelationConcurrently(Oid relationOid)
+ {
+ 	List	   *concurrentIndexIds = NIL,
+ 			   *indexIds = NIL,
+ 			   *parentRelationIds = NIL,
+ 			   *lockTags = NIL,
+ 			   *relationLocks = NIL;
+ 	ListCell   *lc, *lc2;
+ 	Snapshot	snapshot;
+ 	TransactionId limitXmin;
+ 
+ 	/*
+ 	 * Extract the list of indexes that are going to be rebuilt based on the
+ 	 * list of relation Oids given by caller. For each element in given list,
+ 	 * If the relkind of given relation Oid is a table, all its valid indexes
+ 	 * will be rebuilt, including its associated toast table indexes. If
+ 	 * relkind is an index, this index itself will be rebuilt. The locks taken
+ 	 * parent relations and involved indexes are kept until this transaction
+ 	 * is committed to protect against schema changes that might occur until
+ 	 * the session lock is taken on each relation.
+ 	 */
+ 	switch (get_rel_relkind(relationOid))
+ 	{
+ 		case RELKIND_RELATION:
+ 		case RELKIND_MATVIEW:
+ 			{
+ 				/*
+ 				 * In the case of a relation, find all its indexes
+ 				 * including toast indexes.
+ 				 */
+ 				Relation	heapRelation = heap_open(relationOid,
+ 													ShareUpdateExclusiveLock);
+ 
+ 				/* Track this relation for session locks */
+ 				parentRelationIds = lappend_oid(parentRelationIds, relationOid);
+ 
+ 				/* Relation on which is based index cannot be shared */
+ 				if (heapRelation->rd_rel->relisshared)
+ 					ereport(ERROR,
+ 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ 							 errmsg("concurrent reindex is not supported for shared relations")));
+ 
+ 				/* Add all the valid indexes of relation to list */
+ 				foreach(lc2, RelationGetIndexList(heapRelation))
+ 				{
+ 					Oid			cellOid = lfirst_oid(lc2);
+ 					Relation	indexRelation = index_open(cellOid,
+ 													ShareUpdateExclusiveLock);
+ 
+ 					if (!indexRelation->rd_index->indisvalid)
+ 						ereport(WARNING,
+ 								(errcode(ERRCODE_INDEX_CORRUPTED),
+ 								 errmsg("cannot reindex concurrently invalid index \"%s.%s\", skipping",
+ 										get_namespace_name(get_rel_namespace(cellOid)),
+ 										get_rel_name(cellOid))));
+ 					else
+ 						indexIds = lappend_oid(indexIds, cellOid);
+ 
+ 					index_close(indexRelation, NoLock);
+ 				}
+ 
+ 				/* Also add the toast indexes */
+ 				if (OidIsValid(heapRelation->rd_rel->reltoastrelid))
+ 				{
+ 					Oid			toastOid = heapRelation->rd_rel->reltoastrelid;
+ 					Relation	toastRelation = heap_open(toastOid,
+ 												ShareUpdateExclusiveLock);
+ 
+ 					/* Track this relation for session locks */
+ 					parentRelationIds = lappend_oid(parentRelationIds, toastOid);
+ 
+ 					foreach(lc2, RelationGetIndexList(toastRelation))
+ 					{
+ 						Oid			cellOid = lfirst_oid(lc2);
+ 						Relation	indexRelation = index_open(cellOid,
+ 													ShareUpdateExclusiveLock);
+ 
+ 						if (!indexRelation->rd_index->indisvalid)
+ 							ereport(WARNING,
+ 									(errcode(ERRCODE_INDEX_CORRUPTED),
+ 									 errmsg("cannot reindex concurrently invalid index \"%s.%s\", skipping",
+ 											get_namespace_name(get_rel_namespace(cellOid)),
+ 											get_rel_name(cellOid))));
+ 						else
+ 							indexIds = lappend_oid(indexIds, cellOid);
+ 
+ 						index_close(indexRelation, NoLock);
+ 					}
+ 
+ 					heap_close(toastRelation, NoLock);
+ 				}
+ 
+ 				heap_close(heapRelation, NoLock);
+ 				break;
+ 			}
+ 		case RELKIND_INDEX:
+ 			{
+ 				/*
+ 				 * For an index simply add its Oid to list. Invalid indexes
+ 				 * cannot be included in list.
+ 				 */
+ 				Relation	indexRelation = index_open(relationOid, ShareUpdateExclusiveLock);
+ 
+ 				/* Track the parent relation of this index for session locks */
+ 				parentRelationIds = list_make1_oid(IndexGetRelation(relationOid, false));
+ 
+ 				if (!indexRelation->rd_index->indisvalid)
+ 					ereport(WARNING,
+ 							(errcode(ERRCODE_INDEX_CORRUPTED),
+ 							 errmsg("cannot reindex concurrently invalid index \"%s.%s\", skipping",
+ 									get_namespace_name(get_rel_namespace(relationOid)),
+ 									get_rel_name(relationOid))));
+ 				else
+ 					indexIds = list_make1_oid(relationOid);
+ 
+ 				index_close(indexRelation, NoLock);
+ 				break;
+ 			}
+ 		default:
+ 			/* Return error if type of relation is not supported */
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+ 					 errmsg("cannot reindex concurrently this type of relation")));
+ 			break;
+ 	}
+ 
+ 	/* Definetely no indexes, so leave */
+ 	if (indexIds == NIL)
+ 		return false;
+ 
+ 	Assert(parentRelationIds != NIL);
+ 
+ 	/*
+ 	 * Phase 1 of REINDEX CONCURRENTLY
+ 	 *
+ 	 * Here begins the process for rebuilding concurrently the indexes.
+ 	 * We need first to create an index which is based on the same data
+ 	 * as the former index except that it will be only registered in catalogs
+ 	 * and will be built after. It is possible to perform all the operations
+ 	 * on all the indexes at the same time for a parent relation including
+ 	 * its indexes for toast relation.
+ 	 */
+ 
+ 	/* Do the concurrent index creation for each index */
+ 	foreach(lc, indexIds)
+ 	{
+ 		char	   *concurrentName;
+ 		Oid			indOid = lfirst_oid(lc);
+ 		Oid			concurrentOid = InvalidOid;
+ 		Relation	indexRel,
+ 					indexParentRel,
+ 					indexConcurrentRel;
+ 		LockRelId	lockrelid;
+ 
+ 		indexRel = index_open(indOid, ShareUpdateExclusiveLock);
+ 		/* Open the index parent relation, might be a toast or parent relation */
+ 		indexParentRel = heap_open(indexRel->rd_index->indrelid,
+ 								   ShareUpdateExclusiveLock);
+ 
+ 		/* Choose a relation name for concurrent index */
+ 		concurrentName = ChooseIndexName(get_rel_name(indOid),
+ 										 get_rel_namespace(indexRel->rd_index->indrelid),
+ 										 NULL,
+ 										 false,
+ 										 false,
+ 										 false,
+ 										 true);
+ 
+ 		/* Create concurrent index based on given index */
+ 		concurrentOid = index_concurrent_create(indexParentRel,
+ 												indOid,
+ 												concurrentName);
+ 
+ 		/*
+ 		 * Now open the relation of concurrent index, a lock is also needed on
+ 		 * it
+ 		 */
+ 		indexConcurrentRel = index_open(concurrentOid, ShareUpdateExclusiveLock);
+ 
+ 		/* Save the concurrent index Oid */
+ 		concurrentIndexIds = lappend_oid(concurrentIndexIds, concurrentOid);
+ 
+ 		/*
+ 		 * Save lockrelid to protect each concurrent relation from drop then
+ 		 * close relations. The lockrelid on parent relation is not taken here
+ 		 * to avoid multiple locks taken on the same relation, instead we rely
+ 		 * on parentRelationIds built earlier.
+ 		 */
+ 		lockrelid = indexRel->rd_lockInfo.lockRelId;
+ 		relationLocks = lappend(relationLocks, &lockrelid);
+ 		lockrelid = indexConcurrentRel->rd_lockInfo.lockRelId;
+ 		relationLocks = lappend(relationLocks, &lockrelid);
+ 
+ 		index_close(indexRel, NoLock);
+ 		index_close(indexConcurrentRel, NoLock);
+ 		heap_close(indexParentRel, NoLock);
+ 	}
+ 
+ 	/*
+ 	 * Save the heap lock for following visibility checks with other backends
+ 	 * might conflict with this session.
+ 	 */
+ 	foreach(lc, parentRelationIds)
+ 	{
+ 		Relation	heapRelation = heap_open(lfirst_oid(lc), ShareUpdateExclusiveLock);
+ 		LockRelId	lockrelid = heapRelation->rd_lockInfo.lockRelId;
+ 		LOCKTAG		*heaplocktag = (LOCKTAG *) palloc(sizeof(LOCKTAG));
+ 
+ 		/* Add lockrelid of parent relation to the list of locked relations */
+ 		relationLocks = lappend(relationLocks, &lockrelid);
+ 
+ 		/* Save the LOCKTAG for this parent relation for the wait phase */
+ 		SET_LOCKTAG_RELATION(*heaplocktag, lockrelid.dbId, lockrelid.relId);
+ 		lockTags = lappend(lockTags, heaplocktag);
+ 
+ 		/* Close heap relation */
+ 		heap_close(heapRelation, NoLock);
+ 	}
+ 
+ 	/*
+ 	 * For a concurrent build, it is necessary to make the catalog entries
+ 	 * visible to the other transactions before actually building the index.
+ 	 * This will prevent them from making incompatible HOT updates. The index
+ 	 * is marked as not ready and invalid so as no other transactions will try
+ 	 * to use it for INSERT or SELECT.
+ 	 *
+ 	 * Before committing, get a session level lock on the relation, the
+ 	 * concurrent index and its copy to insure that none of them are dropped
+ 	 * until the operation is done.
+ 	 */
+ 	foreach(lc, relationLocks)
+ 	{
+ 		LockRelId lockRel = * (LockRelId *) lfirst(lc);
+ 		LockRelationIdForSession(&lockRel, ShareUpdateExclusiveLock);
+ 	}
+ 
+ 	PopActiveSnapshot();
+ 	CommitTransactionCommand();
+ 
+ 	/*
+ 	 * Phase 2 of REINDEX CONCURRENTLY
+ 	 *
+ 	 * Build concurrent indexes in a separate transaction for each index to
+ 	 * avoid having open transactions for an unnecessary long time. A
+ 	 * concurrent build is done for each concurrent index that will replace
+ 	 * the old indexes. Before doing that, we need to wait on the parent
+ 	 * relations until no running transactions could have the parent table
+ 	 * of index open.
+ 	 */
+ 
+ 	/* Perform a wait on all the session locks */
+ 	StartTransactionCommand();
+ 	WaitForMultipleVirtualLocks(lockTags, ShareLock);
+ 	CommitTransactionCommand();
+ 
+ 	forboth(lc, indexIds, lc2, concurrentIndexIds)
+ 	{
+ 		Relation	indexRel;
+ 		Oid			indOid = lfirst_oid(lc);
+ 		Oid			concurrentOid = lfirst_oid(lc2);
+ 		bool		primary;
+ 
+ 		/* Check for any process interruption */
+ 		CHECK_FOR_INTERRUPTS();
+ 
+ 		/* Start new transaction for this index concurrent build */
+ 		StartTransactionCommand();
+ 
+ 		/* Set ActiveSnapshot since functions in the indexes may need it */
+ 		PushActiveSnapshot(GetTransactionSnapshot());
+ 
+ 		/* Index relation has been closed by previous commit, so reopen it */
+ 		indexRel = index_open(indOid, ShareUpdateExclusiveLock);
+ 		primary = indexRel->rd_index->indisprimary;
+ 		index_close(indexRel, ShareUpdateExclusiveLock);
+ 
+ 		/* Perform concurrent build of new index */
+ 		index_concurrent_build(indexRel->rd_index->indrelid,
+ 							   concurrentOid,
+ 							   primary);
+ 
+ 		/*
+ 		 * Update the pg_index row of the concurrent index as ready for inserts.
+ 		 * Once we commit this transaction, any new transactions that open the
+ 		 * table must insert new entries into the index for insertions and
+ 		 * non-HOT updates.
+ 		 */
+ 		index_set_state_flags(concurrentOid, INDEX_CREATE_SET_READY, true);
+ 
+ 		/* we can do away with our snapshot */
+ 		PopActiveSnapshot();
+ 
+ 		/*
+ 		 * Commit this transaction to make the indisready update visible for
+ 		 * concurrent index.
+ 		 */
+ 		CommitTransactionCommand();
+ 	}
+ 
+ 
+ 	/*
+ 	 * Phase 3 of REINDEX CONCURRENTLY
+ 	 *
+ 	 * During this phase the concurrent indexes catch up with the INSERT that
+ 	 * might have occurred in the parent table.
+ 	 *
+ 	 * We once again wait until no transaction can have the table open with
+ 	 * the index marked as read-only for updates. Each index validation is done
+ 	 * with a separate transaction to avoid opening transaction for an
+ 	 * unnecessary too long time.
+ 	 */
+ 
+ 	/* Perform a wait on all the session locks */
+ 	StartTransactionCommand();
+ 	WaitForMultipleVirtualLocks(lockTags, ShareLock);
+ 	CommitTransactionCommand();
+ 
+ 	/*
+ 	 * Perform a scan of each concurrent index with the heap, then insert
+ 	 * any missing index entries.
+ 	 */
+ 	foreach(lc, concurrentIndexIds)
+ 	{
+ 		Oid indOid = lfirst_oid(lc);
+ 		Oid relOid;
+ 
+ 		/* Check for any process interruption */
+ 		CHECK_FOR_INTERRUPTS();
+ 
+ 		/* Open separate transaction to validate index */
+ 		StartTransactionCommand();
+ 
+ 		/* Get the parent relation Oid */
+ 		relOid = IndexGetRelation(indOid, false);
+ 
+ 		/*
+ 		 * Take the reference snapshot that will be used for the concurrent indexes
+ 		 * validation.
+ 		 */
+ 		snapshot = RegisterSnapshot(GetTransactionSnapshot());
+ 		PushActiveSnapshot(snapshot);
+ 
+ 		/* Validate index, which might be a toast */
+ 		validate_index(relOid, indOid, snapshot);
+ 
+ 		/*
+ 		 * We can now do away with our active snapshot, we still need to save the xmin
+ 		 * limit to wait for older snapshots.
+ 		 */
+ 		limitXmin = snapshot->xmin;
+ 		PopActiveSnapshot();
+ 
+ 		/* And we can remove the validating snapshot too */
+ 		UnregisterSnapshot(snapshot);
+ 
+ 		/*
+ 		 * This concurrent index is now valid as they contain all the tuples
+ 		 * necessary. However, it might not have taken into account deleted tuples
+ 		 * before the reference snapshot was taken, so we need to wait for the
+ 		 * transactions that might have older snapshots than ours.
+ 		 */
+ 		WaitForOldSnapshots(limitXmin);
+ 
+ 		/* Commit this transaction to make the concurrent index valid */
+ 		CommitTransactionCommand();
+ 	}
+ 
+ 	/*
+ 	 * Phase 4 of REINDEX CONCURRENTLY
+ 	 *
+ 	 * Now that the concurrent indexes are valid and can be used, we need to
+ 	 * swap each concurrent index with its corresponding old index. The
+ 	 * concurrent index is marked as valid before performing the swap, and
+ 	 * is invalidated once the swap is done, making it not usable by other
+ 	 * backends once its associated transaction is committed.
+ 	 */
+ 
+ 	/* Swap the indexes and mark the indexes that have the old data as invalid */
+ 	forboth(lc, indexIds, lc2, concurrentIndexIds)
+ 	{
+ 		Oid			indOid = lfirst_oid(lc);
+ 		Oid			concurrentOid = lfirst_oid(lc2);
+ 		Relation	indexRel, indexParentRel;
+ 
+ 		/* Check for any process interruption */
+ 		CHECK_FOR_INTERRUPTS();
+ 
+ 		/*
+ 		 * Each index needs to be swapped in a separate transaction, so start
+ 		 * a new one.
+ 		 */
+ 		StartTransactionCommand();
+ 
+ 		/*
+ 		 * Mark the cache of associated relation as invalid, open relation
+ 		 * relations. AccessExclusive Lock is taken here and not a lower lock
+ 		 * to reduce likelihood of deadlock as ShareUpdateExclusiveLock is
+ 		 * already taken within session.
+ 		 */
+ 		indexRel = index_open(indOid, AccessExclusiveLock);
+ 		indexParentRel = heap_open(indexRel->rd_index->indrelid,
+ 								   AccessExclusiveLock);
+ 
+ 		/*
+ 		 * Concurrent index can now be marked as valid before performing
+ 		 * the swap. Note here that as an exclusive lock is taken on the
+ 		 * relations involved it is safer to call this function as it would
+ 		 * be for a non-concurrent context.
+ 		 * Note: With MVCC catalog access, a lower lock would be enough.
+ 		 */
+ 		index_set_state_flags(concurrentOid, INDEX_CREATE_SET_VALID, false);
+ 
+ 		/* Swap old index and its concurrent */
+ 		index_concurrent_swap(concurrentOid, indOid);
+ 
+ 		/*
+ 		 * Now mark the old index as invalid, the swap is done.
+ 		 */
+ 		index_concurrent_clear_valid(indexParentRel, concurrentOid, false);
+ 
+ 		/*
+ 		 * Invalidate the relcache for the table, so that after this commit
+ 		 * all sessions will refresh any cached plans that might reference the
+ 		 * index.
+ 		 */
+ 		CacheInvalidateRelcache(indexParentRel);
+ 
+ 		/* Close relations opened previously for cache invalidation */
+ 		index_close(indexRel, NoLock);
+ 		heap_close(indexParentRel, NoLock);
+ 
+ 		/* Commit this transaction and make old index invalidation visible */
+ 		CommitTransactionCommand();
+ 	}
+ 
+ 	/*
+ 	 * Phase 5 of REINDEX CONCURRENTLY
+ 	 *
+ 	 * The concurrent indexes now hold the old relfilenode of the other indexes
+ 	 * transactions that might use them. Each operation is performed with a
+ 	 * separate transaction.
+ 	 */
+ 
+ 	/* Now mark the concurrent indexes as not ready */
+ 	foreach(lc, concurrentIndexIds)
+ 	{
+ 		Oid			indOid = lfirst_oid(lc);
+ 		Oid			relOid;
+ 		LOCKTAG	   *heapLockTag = NULL;
+ 		ListCell   *cell;
+ 
+ 		/* Check for any process interruption */
+ 		CHECK_FOR_INTERRUPTS();
+ 
+ 		StartTransactionCommand();
+ 		relOid = IndexGetRelation(indOid, false);
+ 
+ 		/*
+ 		 * Find the locktag of parent table for this index, we need to wait for
+ 		 * locks on it.
+ 		 */
+ 		foreach(cell, lockTags)
+ 		{
+ 			LOCKTAG *localTag = (LOCKTAG *) lfirst(cell);
+ 			if (relOid == localTag->locktag_field2)
+ 				heapLockTag = localTag;
+ 		}
+ 		Assert(heapLockTag && heapLockTag->locktag_field2 != InvalidOid);
+ 
+ 		/*
+ 		 * Finish the index invalidation and set it as dead. Note that it is
+ 		 * necessary to wait for for virtual locks on the parent relation
+ 		 * before setting the index as dead.
+ 		 */
+ 		index_concurrent_set_dead(indOid, relOid, *heapLockTag);
+ 
+ 		/* Commit this transaction to make the update visible. */
+ 		CommitTransactionCommand();
+ 	}
+ 
+ 	/*
+ 	 * Phase 6 of REINDEX CONCURRENTLY
+ 	 *
+ 	 * Drop the concurrent indexes. This needs to be done through
+ 	 * performDeletion or related dependencies will not be dropped for the old
+ 	 * indexes. The internal mechanism of DROP INDEX CONCURRENTLY is not used
+ 	 * as here the indexes are already considered as dead and invalid, so they
+ 	 * will not be used by other backends.
+ 	 */
+ 	foreach(lc, concurrentIndexIds)
+ 	{
+ 		Oid indexOid = lfirst_oid(lc);
+ 
+ 		/* Check for any process interruption */
+ 		CHECK_FOR_INTERRUPTS();
+ 
+ 		/* Start transaction to drop this index */
+ 		StartTransactionCommand();
+ 
+ 		/* Get fresh snapshot for next step */
+ 		PushActiveSnapshot(GetTransactionSnapshot());
+ 
+ 		/*
+ 		 * Open transaction if necessary, for the first index treated its
+ 		 * transaction has been already opened previously.
+ 		 */
+ 		index_concurrent_drop(indexOid);
+ 
+ 		/* We can do away with our snapshot */
+ 		PopActiveSnapshot();
+ 
+ 		/* Commit this transaction to make the update visible. */
+ 		CommitTransactionCommand();
+ 	}
+ 
+ 	/*
+ 	 * Last thing to do is release the session-level lock on the parent table
+ 	 * and the indexes of table.
+ 	 */
+ 	foreach(lc, relationLocks)
+ 	{
+ 		LockRelId lockRel = * (LockRelId *) lfirst(lc);
+ 		UnlockRelationIdForSession(&lockRel, ShareUpdateExclusiveLock);
+ 	}
+ 
+ 	/* Start a new transaction to finish process properly */
+ 	StartTransactionCommand();
+ 
+ 	/* Get fresh snapshot for the end of process */
+ 	PushActiveSnapshot(GetTransactionSnapshot());
+ 
+ 	return true;
+ }
+ 
+ 
+ /*
   * CheckMutability
   *		Test whether given expression is mutable
   */
***************
*** 1542,1548 **** ChooseRelationName(const char *name1, const char *name2,
  static char *
  ChooseIndexName(const char *tabname, Oid namespaceId,
  				List *colnames, List *exclusionOpNames,
! 				bool primary, bool isconstraint)
  {
  	char	   *indexname;
  
--- 1988,1995 ----
  static char *
  ChooseIndexName(const char *tabname, Oid namespaceId,
  				List *colnames, List *exclusionOpNames,
! 				bool primary, bool isconstraint,
! 				bool concurrent)
  {
  	char	   *indexname;
  
***************
*** 1568,1573 **** ChooseIndexName(const char *tabname, Oid namespaceId,
--- 2015,2027 ----
  									   "key",
  									   namespaceId);
  	}
+ 	else if (concurrent)
+ 	{
+ 		indexname = ChooseRelationName(tabname,
+ 									   NULL,
+ 									   "cct",
+ 									   namespaceId);
+ 	}
  	else
  	{
  		indexname = ChooseRelationName(tabname,
***************
*** 1680,1697 **** ChooseIndexColumnNames(List *indexElems)
   *		Recreate a specific index.
   */
  Oid
! ReindexIndex(RangeVar *indexRelation)
  {
  	Oid			indOid;
  	Oid			heapOid = InvalidOid;
  
! 	/* lock level used here should match index lock reindex_index() */
! 	indOid = RangeVarGetRelidExtended(indexRelation, AccessExclusiveLock,
! 									  false, false,
! 									  RangeVarCallbackForReindexIndex,
! 									  (void *) &heapOid);
  
! 	reindex_index(indOid, false);
  
  	return indOid;
  }
--- 2134,2155 ----
   *		Recreate a specific index.
   */
  Oid
! ReindexIndex(RangeVar *indexRelation, bool concurrent)
  {
  	Oid			indOid;
  	Oid			heapOid = InvalidOid;
  
! 	indOid = RangeVarGetRelidExtended(indexRelation,
! 				concurrent ? ShareUpdateExclusiveLock : AccessExclusiveLock,
! 				false, false,
! 				RangeVarCallbackForReindexIndex,
! 				(void *) &heapOid);
  
! 	/* Continue process for concurrent or non-concurrent case */
! 	if (!concurrent)
! 		reindex_index(indOid, false);
! 	else
! 		ReindexRelationConcurrently(indOid);
  
  	return indOid;
  }
***************
*** 1760,1772 **** RangeVarCallbackForReindexIndex(const RangeVar *relation,
   *		Recreate all indexes of a table (and of its toast table, if any)
   */
  Oid
! ReindexTable(RangeVar *relation)
  {
  	Oid			heapOid;
  
  	/* The lock level used here should match reindex_relation(). */
! 	heapOid = RangeVarGetRelidExtended(relation, ShareLock, false, false,
! 									   RangeVarCallbackOwnsTable, NULL);
  
  	if (!reindex_relation(heapOid, REINDEX_REL_PROCESS_TOAST))
  		ereport(NOTICE,
--- 2218,2244 ----
   *		Recreate all indexes of a table (and of its toast table, if any)
   */
  Oid
! ReindexTable(RangeVar *relation, bool concurrent)
  {
  	Oid			heapOid;
  
  	/* The lock level used here should match reindex_relation(). */
! 	heapOid = RangeVarGetRelidExtended(relation,
! 		concurrent ? ShareUpdateExclusiveLock : ShareLock,
! 		false, false,
! 		RangeVarCallbackOwnsTable, NULL);
! 
! 	/* Run through the concurrent process if necessary */
! 	if (concurrent)
! 	{
! 		if (!ReindexRelationConcurrently(heapOid))
! 		{
! 			ereport(NOTICE,
! 					(errmsg("table \"%s\" has no indexes",
! 							relation->relname)));
! 		}
! 		return heapOid;
! 	}
  
  	if (!reindex_relation(heapOid, REINDEX_REL_PROCESS_TOAST))
  		ereport(NOTICE,
***************
*** 1785,1791 **** ReindexTable(RangeVar *relation)
   * That means this must not be called within a user transaction block!
   */
  Oid
! ReindexDatabase(const char *databaseName, bool do_system, bool do_user)
  {
  	Relation	relationRelation;
  	HeapScanDesc scan;
--- 2257,2266 ----
   * That means this must not be called within a user transaction block!
   */
  Oid
! ReindexDatabase(const char *databaseName,
! 				bool do_system,
! 				bool do_user,
! 				bool concurrent)
  {
  	Relation	relationRelation;
  	HeapScanDesc scan;
***************
*** 1797,1802 **** ReindexDatabase(const char *databaseName, bool do_system, bool do_user)
--- 2272,2286 ----
  
  	AssertArg(databaseName);
  
+ 	/*
+ 	 * CONCURRENTLY operation is not allowed for a system, but it is for a
+ 	 * database.
+ 	 */
+ 	if (concurrent && !do_user)
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ 				 errmsg("cannot reindex system concurrently")));
+ 
  	if (strcmp(databaseName, get_database_name(MyDatabaseId)) != 0)
  		ereport(ERROR,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
***************
*** 1880,1894 **** ReindexDatabase(const char *databaseName, bool do_system, bool do_user)
  	foreach(l, relids)
  	{
  		Oid			relid = lfirst_oid(l);
  
  		StartTransactionCommand();
  		/* functions in indexes may want a snapshot set */
  		PushActiveSnapshot(GetTransactionSnapshot());
! 		if (reindex_relation(relid, REINDEX_REL_PROCESS_TOAST))
  			ereport(NOTICE,
! 					(errmsg("table \"%s.%s\" was reindexed",
  							get_namespace_name(get_rel_namespace(relid)),
! 							get_rel_name(relid))));
  		PopActiveSnapshot();
  		CommitTransactionCommand();
  	}
--- 2364,2403 ----
  	foreach(l, relids)
  	{
  		Oid			relid = lfirst_oid(l);
+ 		bool		result = false;
+ 		bool		process_concurrent;
  
  		StartTransactionCommand();
  		/* functions in indexes may want a snapshot set */
  		PushActiveSnapshot(GetTransactionSnapshot());
! 
! 		/* Determine if relation needs to be processed concurrently */
! 		process_concurrent = concurrent &&
! 			!IsSystemNamespace(get_rel_namespace(relid));
! 
! 		/*
! 		 * Reindex relation with a concurrent or non-concurrent process.
! 		 * System relations cannot be reindexed concurrently, but they
! 		 * need to be reindexed including pg_class with a normal process
! 		 * as they could be corrupted, and concurrent process might also
! 		 * use them. This does not include toast relations, which are
! 		 * reindexed when their parent relation is processed.
! 		 */
! 		if (process_concurrent)
! 		{
! 			old = MemoryContextSwitchTo(private_context);
! 			result = ReindexRelationConcurrently(relid);
! 			MemoryContextSwitchTo(old);
! 		}
! 		else
! 			result = reindex_relation(relid, REINDEX_REL_PROCESS_TOAST);
! 
! 		if (result)
  			ereport(NOTICE,
! 					(errmsg("table \"%s.%s\" was reindexed%s",
  							get_namespace_name(get_rel_namespace(relid)),
! 							get_rel_name(relid),
! 							process_concurrent ? " concurrently" : "")));
  		PopActiveSnapshot();
  		CommitTransactionCommand();
  	}
*** a/src/backend/commands/tablecmds.c
--- b/src/backend/commands/tablecmds.c
***************
*** 900,905 **** RangeVarCallbackForDropRelation(const RangeVar *rel, Oid relOid, Oid oldRelOid,
--- 900,937 ----
  	if (classform->relkind != relkind)
  		DropErrorMsgWrongType(rel->relname, classform->relkind, relkind);
  
+ 	/*
+ 	 * Check the case of a system index that might have been invalidated by a
+ 	 * failed concurrent process and allow its drop. For the time being, this
+ 	 * only concerns indexes of toast relations that became invalid during a
+ 	 * REINDEX CONCURRENTLY process.
+ 	 */
+ 	if (IsSystemClass(classform) &&
+ 		relkind == RELKIND_INDEX)
+ 	{
+ 		HeapTuple		locTuple;
+ 		Form_pg_index	indexform;
+ 		bool			indisvalid;
+ 
+ 		locTuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(state->heapOid));
+ 		if (!HeapTupleIsValid(locTuple))
+ 		{
+ 			ReleaseSysCache(tuple);
+ 			return;
+ 		}
+ 
+ 		indexform = (Form_pg_index) GETSTRUCT(locTuple);
+ 		indisvalid = indexform->indisvalid;
+ 		ReleaseSysCache(locTuple);
+ 
+ 		/* Leave if index entry is not valid */
+ 		if (!indisvalid)
+ 		{
+ 			ReleaseSysCache(tuple);
+ 			return;
+ 		}
+ 	}
+ 
  	/* Allow DROP to either table owner or schema owner */
  	if (!pg_class_ownercheck(relOid, GetUserId()) &&
  		!pg_namespace_ownercheck(classform->relnamespace, GetUserId()))
*** a/src/backend/executor/execUtils.c
--- b/src/backend/executor/execUtils.c
***************
*** 1201,1206 **** check_exclusion_constraint(Relation heap, Relation index, IndexInfo *indexInfo,
--- 1201,1220 ----
  	}
  
  	/*
+ 	 * As an invalid index only exists when created in a concurrent context,
+ 	 * and that this code path cannot be taken by CREATE INDEX CONCURRENTLY
+ 	 * as this feature is not available for exclusion constraints, this code
+ 	 * path can only be taken by REINDEX CONCURRENTLY. In this case the same
+ 	 * index exists in parallel to this one so we can bypass this check as
+ 	 * it has already been done on the other index existing in parallel.
+ 	 * If exclusion constraints are supported in the future for CREATE INDEX
+ 	 * CONCURRENTLY, this should be removed or completed especially for this
+ 	 * purpose.
+ 	 */
+ 	if (!index->rd_index->indisvalid)
+ 		return true;
+ 
+ 	/*
  	 * Search the tuples that are in the index for any violations, including
  	 * tuples that aren't visible yet.
  	 */
*** a/src/backend/nodes/copyfuncs.c
--- b/src/backend/nodes/copyfuncs.c
***************
*** 3617,3622 **** _copyReindexStmt(const ReindexStmt *from)
--- 3617,3623 ----
  	COPY_STRING_FIELD(name);
  	COPY_SCALAR_FIELD(do_system);
  	COPY_SCALAR_FIELD(do_user);
+ 	COPY_SCALAR_FIELD(concurrent);
  
  	return newnode;
  }
*** a/src/backend/nodes/equalfuncs.c
--- b/src/backend/nodes/equalfuncs.c
***************
*** 1839,1844 **** _equalReindexStmt(const ReindexStmt *a, const ReindexStmt *b)
--- 1839,1845 ----
  	COMPARE_STRING_FIELD(name);
  	COMPARE_SCALAR_FIELD(do_system);
  	COMPARE_SCALAR_FIELD(do_user);
+ 	COMPARE_SCALAR_FIELD(concurrent);
  
  	return true;
  }
*** a/src/backend/parser/gram.y
--- b/src/backend/parser/gram.y
***************
*** 6752,6780 **** opt_if_exists: IF_P EXISTS						{ $$ = TRUE; }
   *****************************************************************************/
  
  ReindexStmt:
! 			REINDEX reindex_type qualified_name opt_force
  				{
  					ReindexStmt *n = makeNode(ReindexStmt);
  					n->kind = $2;
! 					n->relation = $3;
  					n->name = NULL;
  					$$ = (Node *)n;
  				}
! 			| REINDEX SYSTEM_P name opt_force
  				{
  					ReindexStmt *n = makeNode(ReindexStmt);
  					n->kind = OBJECT_DATABASE;
! 					n->name = $3;
  					n->relation = NULL;
  					n->do_system = true;
  					n->do_user = false;
  					$$ = (Node *)n;
  				}
! 			| REINDEX DATABASE name opt_force
  				{
  					ReindexStmt *n = makeNode(ReindexStmt);
  					n->kind = OBJECT_DATABASE;
! 					n->name = $3;
  					n->relation = NULL;
  					n->do_system = true;
  					n->do_user = true;
--- 6752,6783 ----
   *****************************************************************************/
  
  ReindexStmt:
! 			REINDEX reindex_type opt_concurrently qualified_name opt_force
  				{
  					ReindexStmt *n = makeNode(ReindexStmt);
  					n->kind = $2;
! 					n->concurrent = $3;
! 					n->relation = $4;
  					n->name = NULL;
  					$$ = (Node *)n;
  				}
! 			| REINDEX SYSTEM_P opt_concurrently name opt_force
  				{
  					ReindexStmt *n = makeNode(ReindexStmt);
  					n->kind = OBJECT_DATABASE;
! 					n->concurrent = $3;
! 					n->name = $4;
  					n->relation = NULL;
  					n->do_system = true;
  					n->do_user = false;
  					$$ = (Node *)n;
  				}
! 			| REINDEX DATABASE opt_concurrently name opt_force
  				{
  					ReindexStmt *n = makeNode(ReindexStmt);
  					n->kind = OBJECT_DATABASE;
! 					n->concurrent = $3;
! 					n->name = $4;
  					n->relation = NULL;
  					n->do_system = true;
  					n->do_user = true;
*** a/src/backend/storage/ipc/procarray.c
--- b/src/backend/storage/ipc/procarray.c
***************
*** 2526,2531 **** XidCacheRemoveRunningXids(TransactionId xid,
--- 2526,2677 ----
  	LWLockRelease(ProcArrayLock);
  }
  
+ 
+ /*
+  * WaitForMultipleVirtualLocks
+  *
+  * Wait until no transactions hold the relation related to lock those locks.
+  * To do this, inquire which xacts currently would conflict with each lock on
+  * the table referred by the respective LOCKTAG -- ie, which ones have a lock
+  * that permits writing the relation. Then wait for each of these xacts to
+  * commit or abort.
+  *
+  * To do this, inquire which xacts currently would conflict with lockmode
+  * on the relation.
+  *
+  * Note: GetLockConflicts() never reports our own xid, hence we need not
+  * check for that.  Also, prepared xacts are not reported, which is fine
+  * since they certainly aren't going to do anything more.
+  */
+ void
+ WaitForMultipleVirtualLocks(List *locktags, LOCKMODE lockmode)
+ {
+ 	VirtualTransactionId **old_lockholders;
+ 	int i, count = 0;
+ 	ListCell *lc;
+ 
+ 	/* Leave if no locks to wait for */
+ 	if (list_length(locktags) == 0)
+ 		return;
+ 
+ 	old_lockholders = (VirtualTransactionId **)
+ 		palloc(list_length(locktags) * sizeof(VirtualTransactionId *));
+ 
+ 	/* Collect the transactions we need to wait on for each relation lock */
+ 	foreach(lc, locktags)
+ 	{
+ 		LOCKTAG *locktag = lfirst(lc);
+ 		old_lockholders[count++] = GetLockConflicts(locktag, lockmode);
+ 	}
+ 
+ 	/* Finally wait for each transaction to complete */
+ 	for (i = 0; i < count; i++)
+ 	{
+ 		VirtualTransactionId *lockholders = old_lockholders[i];
+ 
+ 		while (VirtualTransactionIdIsValid(*lockholders))
+ 		{
+ 			VirtualXactLock(*lockholders, true);
+ 			lockholders++;
+ 		}
+ 	}
+ 
+ 	pfree(old_lockholders);
+ }
+ 
+ 
+ /*
+  * WaitForVirtualLocks
+  *
+  * Similar to WaitForMultipleVirtualLocks, but for a single lock.
+  */
+ void
+ WaitForVirtualLocks(LOCKTAG heaplocktag, LOCKMODE lockmode)
+ {
+ 	WaitForMultipleVirtualLocks(list_make1(&heaplocktag), lockmode);
+ }
+ 
+ 
+ /*
+  * WaitForOldSnapshots
+  *
+  * Wait for transactions that might have older snapshot than the given xmin
+  * limit, because it might not contain tuples deleted just before it has
+  * been taken. Obtain a list of VXIDs of such transactions, and wait for them
+  * individually.
+  *
+  * We can exclude any running transactions that have xmin > the xmin given;
+  * their oldest snapshot must be newer than our xmin limit.
+  * We can also exclude any transactions that have xmin = zero, since they
+  * evidently have no live snapshot at all (and any one they might be in
+  * process of taking is certainly newer than ours).  Transactions in other
+  * DBs can be ignored too, since they'll never even be able to see this
+  * index.
+  *
+  * We can also exclude autovacuum processes and processes running manual
+  * lazy VACUUMs, because they won't be fazed by missing index entries
+  * either. (Manual ANALYZEs, however, can't be excluded because they
+  * might be within transactions that are going to do arbitrary operations
+  * later.)
+  *
+  * Also, GetCurrentVirtualXIDs never reports our own vxid, so we need not
+  * check for that.
+  *
+  * If a process goes idle-in-transaction with xmin zero, we do not need to
+  * wait for it anymore, per the above argument.  We do not have the
+  * infrastructure right now to stop waiting if that happens, but we can at
+  * least avoid the folly of waiting when it is idle at the time we would
+  * begin to wait.  We do this by repeatedly rechecking the output of
+  * GetCurrentVirtualXIDs.  If, during any iteration, a particular vxid
+  * doesn't show up in the output, we know we can forget about it.
+  */
+ void
+ WaitForOldSnapshots(TransactionId limitXmin)
+ {
+ 	int i, n_old_snapshots;
+ 	VirtualTransactionId *old_snapshots;
+ 
+ 	old_snapshots = GetCurrentVirtualXIDs(limitXmin, true, false,
+ 										  PROC_IS_AUTOVACUUM | PROC_IN_VACUUM,
+ 										  &n_old_snapshots);
+ 
+ 	for (i = 0; i < n_old_snapshots; i++)
+ 	{
+ 		if (!VirtualTransactionIdIsValid(old_snapshots[i]))
+ 			continue; /* found uninteresting in previous cycle */
+ 
+ 		if (i > 0)
+ 		{
+ 			/* see if anything's changed ... */
+ 			VirtualTransactionId *newer_snapshots;
+ 			int n_newer_snapshots, j, k;
+ 
+ 			newer_snapshots = GetCurrentVirtualXIDs(limitXmin,
+ 													true, false,
+ 													PROC_IS_AUTOVACUUM | PROC_IN_VACUUM,
+ 													&n_newer_snapshots);
+ 			for (j = i; j < n_old_snapshots; j++)
+ 			{
+ 				if (!VirtualTransactionIdIsValid(old_snapshots[j]))
+ 					continue; /* found uninteresting in previous cycle */
+ 				for (k = 0; k < n_newer_snapshots; k++)
+ 				{
+ 					if (VirtualTransactionIdEquals(old_snapshots[j],
+ 												   newer_snapshots[k]))
+ 					                                              break;
+ 				}
+ 				if (k >= n_newer_snapshots) /* not there anymore */
+ 					SetInvalidVirtualTransactionId(old_snapshots[j]);
+ 			}
+ 			pfree(newer_snapshots);
+ 		}
+ 
+ 		if (VirtualTransactionIdIsValid(old_snapshots[i]))
+ 			VirtualXactLock(old_snapshots[i], true);
+ 	}
+ }
+ 
+ 
  #ifdef XIDCACHE_DEBUG
  
  /*
*** a/src/backend/tcop/utility.c
--- b/src/backend/tcop/utility.c
***************
*** 778,793 **** standard_ProcessUtility(Node *parsetree,
  			{
  				ReindexStmt *stmt = (ReindexStmt *) parsetree;
  
  				/* we choose to allow this during "read only" transactions */
  				PreventCommandDuringRecovery("REINDEX");
  				switch (stmt->kind)
  				{
  					case OBJECT_INDEX:
! 						ReindexIndex(stmt->relation);
  						break;
  					case OBJECT_TABLE:
  					case OBJECT_MATVIEW:
! 						ReindexTable(stmt->relation);
  						break;
  					case OBJECT_DATABASE:
  
--- 778,797 ----
  			{
  				ReindexStmt *stmt = (ReindexStmt *) parsetree;
  
+ 				if (stmt->concurrent)
+ 					PreventTransactionChain(isTopLevel,
+ 											"REINDEX CONCURRENTLY");
+ 
  				/* we choose to allow this during "read only" transactions */
  				PreventCommandDuringRecovery("REINDEX");
  				switch (stmt->kind)
  				{
  					case OBJECT_INDEX:
! 						ReindexIndex(stmt->relation, stmt->concurrent);
  						break;
  					case OBJECT_TABLE:
  					case OBJECT_MATVIEW:
! 						ReindexTable(stmt->relation, stmt->concurrent);
  						break;
  					case OBJECT_DATABASE:
  
***************
*** 799,806 **** standard_ProcessUtility(Node *parsetree,
  						 */
  						PreventTransactionChain(isTopLevel,
  												"REINDEX DATABASE");
! 						ReindexDatabase(stmt->name,
! 										stmt->do_system, stmt->do_user);
  						break;
  					default:
  						elog(ERROR, "unrecognized object type: %d",
--- 803,810 ----
  						 */
  						PreventTransactionChain(isTopLevel,
  												"REINDEX DATABASE");
! 						ReindexDatabase(stmt->name, stmt->do_system,
! 										stmt->do_user, stmt->concurrent);
  						break;
  					default:
  						elog(ERROR, "unrecognized object type: %d",
*** a/src/include/catalog/index.h
--- b/src/include/catalog/index.h
***************
*** 60,66 **** extern Oid index_create(Relation heapRelation,
  			 bool allow_system_table_mods,
  			 bool skip_build,
  			 bool concurrent,
! 			 bool is_internal);
  
  extern void index_constraint_create(Relation heapRelation,
  						Oid indexRelationId,
--- 60,87 ----
  			 bool allow_system_table_mods,
  			 bool skip_build,
  			 bool concurrent,
! 			 bool is_internal,
! 			 bool is_reindex);
! 
! extern Oid index_concurrent_create(Relation heapRelation,
! 								   Oid indOid,
! 								   char *concurrentName);
! 
! extern void index_concurrent_build(Oid heapOid,
! 								   Oid indexOid,
! 								   bool isprimary);
! 
! extern void index_concurrent_swap(Oid newIndexOid, Oid oldIndexOid);
! 
! extern void index_concurrent_set_dead(Oid indexId,
! 									  Oid heapId,
! 									  LOCKTAG locktag);
! 
! extern void index_concurrent_clear_valid(Relation heapRelation,
! 										 Oid indexOid,
! 										 bool concurrent);
! 
! extern void index_concurrent_drop(Oid indexOid);
  
  extern void index_constraint_create(Relation heapRelation,
  						Oid indexRelationId,
***************
*** 100,106 **** extern double IndexBuildHeapScan(Relation heapRelation,
  
  extern void validate_index(Oid heapId, Oid indexId, Snapshot snapshot);
  
! extern void index_set_state_flags(Oid indexId, IndexStateFlagsAction action);
  
  extern void reindex_index(Oid indexId, bool skip_constraint_checks);
  
--- 121,129 ----
  
  extern void validate_index(Oid heapId, Oid indexId, Snapshot snapshot);
  
! extern void index_set_state_flags(Oid indexId,
! 								  IndexStateFlagsAction action,
! 								  bool concurrent);
  
  extern void reindex_index(Oid indexId, bool skip_constraint_checks);
  
*** a/src/include/commands/defrem.h
--- b/src/include/commands/defrem.h
***************
*** 26,35 **** extern Oid DefineIndex(IndexStmt *stmt,
  			bool check_rights,
  			bool skip_build,
  			bool quiet);
! extern Oid	ReindexIndex(RangeVar *indexRelation);
! extern Oid	ReindexTable(RangeVar *relation);
  extern Oid ReindexDatabase(const char *databaseName,
! 				bool do_system, bool do_user);
  extern char *makeObjectName(const char *name1, const char *name2,
  			   const char *label);
  extern char *ChooseRelationName(const char *name1, const char *name2,
--- 26,36 ----
  			bool check_rights,
  			bool skip_build,
  			bool quiet);
! extern Oid	ReindexIndex(RangeVar *indexRelation, bool concurrent);
! extern Oid	ReindexTable(RangeVar *relation, bool concurrent);
  extern Oid ReindexDatabase(const char *databaseName,
! 							bool do_system, bool do_user, bool concurrent);
! extern bool ReindexRelationConcurrently(Oid relOid);
  extern char *makeObjectName(const char *name1, const char *name2,
  			   const char *label);
  extern char *ChooseRelationName(const char *name1, const char *name2,
*** a/src/include/nodes/parsenodes.h
--- b/src/include/nodes/parsenodes.h
***************
*** 2538,2543 **** typedef struct ReindexStmt
--- 2538,2544 ----
  	const char *name;			/* name of database to reindex */
  	bool		do_system;		/* include system tables in database case */
  	bool		do_user;		/* include user tables in database case */
+ 	bool		concurrent;		/* reindex concurrently? */
  } ReindexStmt;
  
  /* ----------------------
*** a/src/include/storage/procarray.h
--- b/src/include/storage/procarray.h
***************
*** 76,79 **** extern void XidCacheRemoveRunningXids(TransactionId xid,
--- 76,83 ----
  						  int nxids, const TransactionId *xids,
  						  TransactionId latestXid);
  
+ extern void WaitForMultipleVirtualLocks(List *locktags, LOCKMODE lockmode);
+ extern void WaitForVirtualLocks(LOCKTAG heaplocktag, LOCKMODE lockmode);
+ extern void WaitForOldSnapshots(TransactionId limitXmin);
+ 
  #endif   /* PROCARRAY_H */
*** a/src/test/regress/expected/create_index.out
--- b/src/test/regress/expected/create_index.out
***************
*** 2721,2723 **** ORDER BY thousand;
--- 2721,2778 ----
          1 |     1001
  (2 rows)
  
+ --
+ -- Check behavior of REINDEX and REINDEX CONCURRENTLY
+ --
+ CREATE TABLE concur_reindex_tab (c1 int);
+ -- REINDEX
+ REINDEX TABLE concur_reindex_tab; -- notice
+ NOTICE:  table "concur_reindex_tab" has no indexes
+ REINDEX TABLE CONCURRENTLY concur_reindex_tab; -- notice
+ NOTICE:  table "concur_reindex_tab" has no indexes
+ ALTER TABLE concur_reindex_tab ADD COLUMN c2 text; -- add toast index
+ -- Normal index with integer column
+ CREATE UNIQUE INDEX concur_reindex_ind1 ON concur_reindex_tab(c1);
+ -- Normal index with text column
+ CREATE INDEX concur_reindex_ind2 ON concur_reindex_tab(c2);
+ -- UNIQUE index with expression
+ CREATE UNIQUE INDEX concur_reindex_ind3 ON concur_reindex_tab(abs(c1));
+ -- Duplicate column names
+ CREATE INDEX concur_reindex_ind4 ON concur_reindex_tab(c1, c1, c2);
+ -- Create table for check on foreign key dependence switch with indexes swapped
+ ALTER TABLE concur_reindex_tab ADD PRIMARY KEY USING INDEX concur_reindex_ind1;
+ CREATE TABLE concur_reindex_tab2 (c1 int REFERENCES concur_reindex_tab);
+ INSERT INTO concur_reindex_tab VALUES  (1, 'a');
+ INSERT INTO concur_reindex_tab VALUES  (2, 'a');
+ -- Check materialized views
+ CREATE MATERIALIZED VIEW concur_reindex_matview AS SELECT * FROM concur_reindex_tab;
+ REINDEX INDEX CONCURRENTLY concur_reindex_ind1;
+ REINDEX TABLE CONCURRENTLY concur_reindex_tab;
+ REINDEX TABLE CONCURRENTLY concur_reindex_matview;
+ -- Check errors
+ -- Cannot run inside a transaction block
+ BEGIN;
+ REINDEX TABLE CONCURRENTLY concur_reindex_tab;
+ ERROR:  REINDEX CONCURRENTLY cannot run inside a transaction block
+ COMMIT;
+ REINDEX TABLE CONCURRENTLY pg_database; -- no shared relation
+ ERROR:  concurrent reindex is not supported for shared relations
+ REINDEX SYSTEM CONCURRENTLY postgres; -- not allowed for SYSTEM
+ ERROR:  cannot reindex system concurrently
+ -- Check the relation status, there should not be invalid indexes
+ \d concur_reindex_tab
+ Table "public.concur_reindex_tab"
+  Column |  Type   | Modifiers 
+ --------+---------+-----------
+  c1     | integer | not null
+  c2     | text    | 
+ Indexes:
+     "concur_reindex_ind1" PRIMARY KEY, btree (c1)
+     "concur_reindex_ind3" UNIQUE, btree (abs(c1))
+     "concur_reindex_ind2" btree (c2)
+     "concur_reindex_ind4" btree (c1, c1, c2)
+ Referenced by:
+     TABLE "concur_reindex_tab2" CONSTRAINT "concur_reindex_tab2_c1_fkey" FOREIGN KEY (c1) REFERENCES concur_reindex_tab(c1)
+ 
+ DROP MATERIALIZED VIEW concur_reindex_matview;
+ DROP TABLE concur_reindex_tab, concur_reindex_tab2;
*** a/src/test/regress/sql/create_index.sql
--- b/src/test/regress/sql/create_index.sql
***************
*** 912,914 **** ORDER BY thousand;
--- 912,954 ----
  SELECT thousand, tenthous FROM tenk1
  WHERE thousand < 2 AND tenthous IN (1001,3000)
  ORDER BY thousand;
+ 
+ --
+ -- Check behavior of REINDEX and REINDEX CONCURRENTLY
+ --
+ CREATE TABLE concur_reindex_tab (c1 int);
+ -- REINDEX
+ REINDEX TABLE concur_reindex_tab; -- notice
+ REINDEX TABLE CONCURRENTLY concur_reindex_tab; -- notice
+ ALTER TABLE concur_reindex_tab ADD COLUMN c2 text; -- add toast index
+ -- Normal index with integer column
+ CREATE UNIQUE INDEX concur_reindex_ind1 ON concur_reindex_tab(c1);
+ -- Normal index with text column
+ CREATE INDEX concur_reindex_ind2 ON concur_reindex_tab(c2);
+ -- UNIQUE index with expression
+ CREATE UNIQUE INDEX concur_reindex_ind3 ON concur_reindex_tab(abs(c1));
+ -- Duplicate column names
+ CREATE INDEX concur_reindex_ind4 ON concur_reindex_tab(c1, c1, c2);
+ -- Create table for check on foreign key dependence switch with indexes swapped
+ ALTER TABLE concur_reindex_tab ADD PRIMARY KEY USING INDEX concur_reindex_ind1;
+ CREATE TABLE concur_reindex_tab2 (c1 int REFERENCES concur_reindex_tab);
+ INSERT INTO concur_reindex_tab VALUES  (1, 'a');
+ INSERT INTO concur_reindex_tab VALUES  (2, 'a');
+ -- Check materialized views
+ CREATE MATERIALIZED VIEW concur_reindex_matview AS SELECT * FROM concur_reindex_tab;
+ REINDEX INDEX CONCURRENTLY concur_reindex_ind1;
+ REINDEX TABLE CONCURRENTLY concur_reindex_tab;
+ REINDEX TABLE CONCURRENTLY concur_reindex_matview;
+ 
+ -- Check errors
+ -- Cannot run inside a transaction block
+ BEGIN;
+ REINDEX TABLE CONCURRENTLY concur_reindex_tab;
+ COMMIT;
+ REINDEX TABLE CONCURRENTLY pg_database; -- no shared relation
+ REINDEX SYSTEM CONCURRENTLY postgres; -- not allowed for SYSTEM
+ 
+ -- Check the relation status, there should not be invalid indexes
+ \d concur_reindex_tab
+ DROP MATERIALIZED VIEW concur_reindex_matview;
+ DROP TABLE concur_reindex_tab, concur_reindex_tab2;