20130107_reindex_concurrently_v9b.patch

diff --git a/src/backend/bootstrap/bootstrap.c b/src/backend/bootstrap/bootstrap.c
index 82ef726..fe25410 100644
--- a/src/backend/bootstrap/bootstrap.c
+++ b/src/backend/bootstrap/bootstrap.c
@@ -1145,7 +1145,7 @@ build_indices(void)
 		heap = heap_open(ILHead->il_heap, NoLock);
 		ind = index_open(ILHead->il_ind, NoLock);
 
-		index_build(heap, ind, ILHead->il_info, false, false);
+		index_build(heap, ind, ILHead->il_info, false, false, true);
 
 		index_close(ind, NoLock);
 		heap_close(heap, NoLock);
diff --git a/src/backend/catalog/heap.c b/src/backend/catalog/heap.c
index db51e0b..6c7179d 100644
--- a/src/backend/catalog/heap.c
+++ b/src/backend/catalog/heap.c
@@ -2654,7 +2654,7 @@ RelationTruncateIndexes(Relation heapRelation)
 
 		/* Initialize the index and rebuild */
 		/* Note: we do not need to re-establish pkey setting */
-		index_build(heapRelation, currentIndex, indexInfo, false, true);
+		index_build(heapRelation, currentIndex, indexInfo, false, true, true);
 
 		/* We're done with this index */
 		index_close(currentIndex, NoLock);
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 9b33929..448d2ba 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -43,6 +43,7 @@
 #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"
@@ -672,6 +673,10 @@ UpdateIndexRelation(Oid indexoid,
  *		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.
  */
@@ -695,7 +700,8 @@ index_create(Relation heapRelation,
 			 bool allow_system_table_mods,
 			 bool skip_build,
 			 bool concurrent,
-			 bool is_internal)
+			 bool is_internal,
+			 bool is_reindex)
 {
 	Oid			heapRelationId = RelationGetRelid(heapRelation);
 	Relation	pg_class;
@@ -738,19 +744,23 @@ index_create(Relation heapRelation,
 
 	/*
 	 * concurrent index build on a system catalog is unsafe because we tend to
-	 * release locks before committing in catalogs
+	 * 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))
+		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 not supported, but there's no way to ask for it
-	 * in the grammar anyway, so it can't happen.
+	 * in the grammar anyway, so it can't happen. This might be called during a
+	 * conccurrent reindex operation, in this case sufficient locks are already
+	 * taken on the related relations.
 	 */
-	if (concurrent && is_exclusion)
+	if (concurrent && is_exclusion && !is_reindex)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg_internal("concurrent index creation for exclusion constraints is not supported")));
@@ -1084,7 +1094,7 @@ index_create(Relation heapRelation,
 	}
 	else
 	{
-		index_build(heapRelation, indexRelation, indexInfo, isprimary, false);
+		index_build(heapRelation, indexRelation, indexInfo, isprimary, false, true);
 	}
 
 	/*
@@ -1096,6 +1106,395 @@ index_create(Relation heapRelation,
 	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;
+	int			i;
+	HeapTuple	indexTuple;
+	Datum		indclassDatum, indoptionDatum;
+	oidvector  *indclass;
+	int2vector *indcoloptions;
+	bool		isnull;
+	bool		isconstraint;
+	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			constTuple;
+		Form_pg_constraint	constraint;
+
+		constTuple = SearchSysCache1(CONSTROID,
+									 ObjectIdGetDatum(constraintOid));
+		if (!HeapTupleIsValid(constTuple))
+			elog(ERROR, "cache lookup failed for constraint %u",
+				 constraintOid);
+		constraint = (Form_pg_constraint) GETSTRUCT(constTuple);
+		initdeferred = constraint->condeferred;
+
+		ReleaseSysCache(constTuple);
+	}
+
+	/* Build the list of column names, necessary for index_create */
+	for (i = 0; i < indexInfo->ii_NumIndexAttrs; i++)
+	{
+		AttrNumber	attnum = indexInfo->ii_KeyAttrNumbers[i];
+		Form_pg_attribute attform = heapRelation->rd_att->attrs[attnum - 1];;
+
+		/* Pick up column name from the relation */
+		columnNames = lappend(columnNames, pstrdup(NameStr(attform->attname)));
+	}
+
+	/*
+	 * Index is considered as a constraint if it is UNIQUE, PRIMARY  KEY or
+	 * EXCLUSION.
+	 */
+	isconstraint = indexRelation->rd_index->indisunique ||
+		indexRelation->rd_index->indisprimary ||
+		indexRelation->rd_index->indisexclusion;
+
+	/* 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);
+
+	indoptionDatum = SysCacheGetAttr(INDEXRELID, indexTuple,
+									 Anum_pg_index_indoption, &isnull);
+	Assert(!isnull);
+	indcoloptions = (int2vector *) DatumGetPointer(indoptionDatum);
+
+	/* 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,
+								 (Datum) indexRelation->rd_options,
+								 indexRelation->rd_index->indisprimary,
+								 isconstraint,	/* 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, RowExclusiveLock);
+	ReleaseSysCache(indexTuple);
+
+	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 */
+	indexInfo = BuildIndexInfo(indexRelation);
+	Assert(!indexInfo->ii_ReadyForInserts);
+	indexInfo->ii_Concurrent = true;
+	indexInfo->ii_BrokenHotChain = false;
+
+	/*
+	 * Now build the index, in the case of a parent relation being a toast
+	 * relation, its reltoastidxid is updated when calling index_concurrent_swap.
+	 */
+	index_build(rel, indexRelation, indexInfo, isprimary, false, false);
+
+	/* Close both the relations, but keep the locks */
+	heap_close(rel, NoLock);
+	index_close(indexRelation, NoLock);
+}
+
+
+/*
+ * index_concurrent_swap
+ *
+ * Replace old index by old index in a concurrent context. For the time being
+ * what is done here is switching the relation names 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.
+ * For toast indexes, it is also necessary to modify reltoastidxid of the parent
+ * relation so we need also to take RowExclusiveLock in this case until the
+ * end of the transaction block for this relation.
+ */
+void
+index_concurrent_swap(Oid newIndexOid, Oid oldIndexOid)
+{
+	char		   *nameNew, *nameOld, *nameTemp;
+	Oid				parentOid = IndexGetRelation(oldIndexOid, false);
+	Relation		oldIndexRel, newIndexRel, parentRel;
+
+	/*
+	 * If the index swapped is a toast index, take a row exclusive lock on its
+	 * parent toast relation before the involved indexes, it is necessary to
+	 * take a lock before the indexes on the toast table as in this case
+	 * the reltoastidxid is updated to the new index Oid.
+	 */
+	if (get_rel_relkind(parentOid) == RELKIND_TOASTVALUE)
+	{
+		/* Open pg_class and fetch a writable copy of the relation tuple */
+		parentRel = heap_open(parentOid, RowExclusiveLock);
+	}
+
+	/*
+	 * Take a lock on the old and new index before switching their names. This
+	 * avoids having index swapping relying on relation renaming mechanism to
+	 * get a lock on the relations involved.
+	 */
+	oldIndexRel = relation_open(oldIndexOid, AccessExclusiveLock);
+	newIndexRel = relation_open(newIndexOid, AccessExclusiveLock);
+
+	/* Allocate all the names used for this operation */
+	nameNew = get_rel_name(newIndexOid);
+	nameOld = get_rel_name(oldIndexOid);
+	/* Build a unique temporary name */
+	nameTemp = ChooseRelationName((const char *) get_rel_name(oldIndexOid),
+								  NULL,
+								  "tmp",
+								  get_rel_namespace(oldIndexOid));
+
+	/* Change the name of old index to something temporary */
+	RenameRelationInternal(oldIndexOid, nameTemp);
+
+	/* Make the catalog update visible */
+	CommandCounterIncrement();
+
+	/* Change the name of the new index with the old one */
+	RenameRelationInternal(newIndexOid, nameOld);
+
+	/* Make the catalog update visible */
+	CommandCounterIncrement();
+
+	/* Finally change the name of old index with name of the new one */
+	RenameRelationInternal(oldIndexOid, nameNew);
+
+	/* Make the catalog update visible */
+	CommandCounterIncrement();
+
+	/* The lock taken previously is not released until the end of transaction */
+	relation_close(oldIndexRel, NoLock);
+	relation_close(newIndexRel, NoLock);
+
+	/*
+	 * If the index swapped is a toast index, take an exclusive lock on its
+	 * parent toast relation and then update reltoastidxid to the new index Oid
+	 * value.
+	 */
+	if (get_rel_relkind(parentOid) == RELKIND_TOASTVALUE)
+	{
+		/* Update the statistics of this pg_class entry with new toast index Oid */
+		index_update_stats(parentRel, false, false, newIndexOid, -1.0);
+
+		/* Close parent relation */
+		heap_close(parentRel, RowExclusiveLock);
+	}
+
+	/*
+	 * Scan for potential foreign keys on the index being swapped and change its
+	 * dependencies to the new index created concurrently.
+	 */
+	switchIndexConstraintOnForeignKey(parentOid, oldIndexOid, newIndexOid);
+}
+
+/*
+ * 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.
+	 */
+	if (locktag)
+		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);
+
+	/*
+	 * 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.
+ */
+void
+index_concurrent_clear_valid(Relation heapRelation, Oid indexOid)
+{
+	/*
+	 * Mark index invalid by updating its pg_index entry
+	 */
+	index_set_state_flags(indexOid, 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(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 are not dropped. At this point all the indexes are already considered
+ * as invalid and dead so they can be dropped without using any concurrent
+ * options.
+ */
+void
+index_concurrent_drop(Oid indexOid)
+{
+	Oid				constraintOid = get_index_constraint(indexOid);
+	ObjectAddress	object;
+	Form_pg_index	indexForm;
+	Relation		pg_index;
+	HeapTuple		indexTuple;
+	bool			indislive;
+
+	/*
+	 * 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);
+	indislive = indexForm->indislive;
+
+	/* Clean up */
+	heap_close(pg_index, RowExclusiveLock);
+
+	/* Leave if index is still alive */
+	if (indislive)
+		return;
+
+	/*
+	 * 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
  *
@@ -1326,7 +1725,6 @@ 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
@@ -1408,17 +1806,8 @@ 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);
+		/* Mark the index as invalid */
+		index_concurrent_clear_valid(userHeapRelation, indexId);
 
 		/* save lockrelid and locktag for below, then close but keep locks */
 		heaprelid = userHeapRelation->rd_lockInfo.lockRelId;
@@ -1446,63 +1835,8 @@ 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);
+		/* 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
@@ -1515,13 +1849,7 @@ 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++;
-		}
+		WaitForVirtualLocks(heaplocktag, AccessExclusiveLock);
 
 		/*
 		 * Re-open relations to allow us to complete our actions.
@@ -1943,6 +2271,8 @@ index_update_stats(Relation rel,
  *
  * isprimary tells whether to mark the index as a primary-key index.
  * isreindex indicates we are recreating a previously-existing index.
+ * istoastupdate tells whether it is necessary to update the toast index Oid
+ * for parent relation.
  *
  * Note: when reindexing an existing index, isprimary can be false even if
  * the index is a PK; it's already properly marked and need not be re-marked.
@@ -1956,7 +2286,8 @@ index_build(Relation heapRelation,
 			Relation indexRelation,
 			IndexInfo *indexInfo,
 			bool isprimary,
-			bool isreindex)
+			bool isreindex,
+			bool istoastupdate)
 {
 	RegProcedure procedure;
 	IndexBuildResult *stats;
@@ -2071,7 +2402,8 @@ index_build(Relation heapRelation,
 	index_update_stats(heapRelation,
 					   true,
 					   isprimary,
-					   (heapRelation->rd_rel->relkind == RELKIND_TOASTVALUE) ?
+					   (heapRelation->rd_rel->relkind == RELKIND_TOASTVALUE) &&
+							istoastupdate ?
 					   RelationGetRelid(indexRelation) : InvalidOid,
 					   stats->heap_tuples);
 
@@ -3189,7 +3521,7 @@ reindex_index(Oid indexId, bool skip_constraint_checks)
 
 		/* Initialize the index and rebuild */
 		/* Note: we do not need to re-establish pkey setting */
-		index_build(heapRelation, iRel, indexInfo, false, true);
+		index_build(heapRelation, iRel, indexInfo, false, true, true);
 	}
 	PG_CATCH();
 	{
diff --git a/src/backend/catalog/pg_constraint.c b/src/backend/catalog/pg_constraint.c
index 7179fa9..63fa201 100644
--- a/src/backend/catalog/pg_constraint.c
+++ b/src/backend/catalog/pg_constraint.c
@@ -973,3 +973,79 @@ check_functional_grouping(Oid relid,
 
 	return result;
 }
+
+/*
+ * switchIndexConstraintOnForeignKey
+ *
+ * Switch foreign keys references for a given index to a new index created
+ * concurrently. This process is used when swapping indexes for a concurrent
+ * process. All the constraints that are not referenced externally like primary
+ * keys or unique indexes should be switched using the structure of index.c for
+ * concurrent index creation and drop.
+ * This function takes care of also switching the dependencies of the foreign
+ * key from the old index to the new index in pg_depend.
+ *
+ * In order to complete this process, the following process is done:
+ * 1) Scan pg_constraint and extract the list of foreign keys that refer to the
+ * parent relation of the index being swapped as conrelid.
+ * 2) Check in this list the foreign keys that use the old index as reference
+ * here with conindid
+ * 3) Update field conindid to the new index Oid on all the foreign keys
+ * 4) Switch dependencies of the foreign key to the new index
+ */
+void
+switchIndexConstraintOnForeignKey(Oid parentOid,
+								  Oid oldIndexOid,
+								  Oid newIndexOid)
+{
+	ScanKeyData skey[1];
+	SysScanDesc conscan;
+	Relation    conRel;
+	HeapTuple   htup;
+
+	/*
+	 * Search pg_constraint for the foreign key constraints associated
+	 * with the index by scanning using conrelid.
+	 */
+	ScanKeyInit(&skey[0],
+				Anum_pg_constraint_confrelid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(parentOid));
+
+	conRel = heap_open(ConstraintRelationId, AccessShareLock);
+	conscan = systable_beginscan(conRel, ConstraintForeignRelidIndexId,
+								 true, SnapshotNow, 1, skey);
+
+	while (HeapTupleIsValid(htup = systable_getnext(conscan)))
+	{
+		Form_pg_constraint contuple = (Form_pg_constraint) GETSTRUCT(htup);
+
+		/* Check if a foreign constraint uses the index being swapped */
+		if (contuple->contype == CONSTRAINT_FOREIGN &&
+			contuple->confrelid == parentOid &&
+			contuple->conindid == oldIndexOid)
+		{
+			/*
+			 * An index has been found, so first switch  all the dependencies
+			 * of this foreign key from the old index to the new index.
+			 */
+			changeDependencyFor(ConstraintRelationId,
+								HeapTupleGetOid(htup),
+								RelationRelationId,
+								oldIndexOid,
+								newIndexOid);
+
+			/* Then update its pg_constraint entry */
+			htup = heap_copytuple(htup);
+			contuple = (Form_pg_constraint) GETSTRUCT(htup);
+			contuple->conindid = newIndexOid;
+			simple_heap_update(conRel, &htup->t_self, htup);
+
+			/* Update the system catalog indexes */
+			CatalogUpdateIndexes(conRel, htup);
+		}
+	}
+
+	systable_endscan(conscan);
+	heap_close(conRel, AccessShareLock);
+}
diff --git a/src/backend/catalog/toasting.c b/src/backend/catalog/toasting.c
index 7c4ccbd..e8608c4 100644
--- a/src/backend/catalog/toasting.c
+++ b/src/backend/catalog/toasting.c
@@ -280,7 +280,7 @@ 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);
+				 true, false, false, false, false);
 
 	heap_close(toast_rel, NoLock);
 
diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index c3385a1..493a085 100644
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -68,8 +68,9 @@ 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);
+							 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,
@@ -311,7 +312,6 @@ DefineIndex(IndexStmt *stmt,
 	Oid			tablespaceId;
 	List	   *indexColNames;
 	Relation	rel;
-	Relation	indexRelation;
 	HeapTuple	tuple;
 	Form_pg_am	accessMethodForm;
 	bool		amcanorder;
@@ -320,13 +320,9 @@ DefineIndex(IndexStmt *stmt,
 	int16	   *coloptions;
 	IndexInfo  *indexInfo;
 	int			numberOfAttributes;
-	VirtualTransactionId *old_lockholders;
-	VirtualTransactionId *old_snapshots;
-	int			n_old_snapshots;
 	LockRelId	heaprelid;
 	LOCKTAG		heaplocktag;
 	Snapshot	snapshot;
-	int			i;
 
 	/*
 	 * count attributes in index
@@ -452,7 +448,8 @@ DefineIndex(IndexStmt *stmt,
 											indexColNames,
 											stmt->excludeOpNames,
 											stmt->primary,
-											stmt->isconstraint);
+											stmt->isconstraint,
+											false);
 
 	/*
 	 * look up the access method, verify it can handle the requested features
@@ -599,7 +596,7 @@ DefineIndex(IndexStmt *stmt,
 					 stmt->isconstraint, stmt->deferrable, stmt->initdeferred,
 					 allowSystemTableMods,
 					 skip_build || stmt->concurrent,
-					 stmt->concurrent, !check_rights);
+					 stmt->concurrent, !check_rights, false);
 
 	/* Add any requested comment */
 	if (stmt->idxcomment != NULL)
@@ -662,18 +659,8 @@ 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++;
-	}
+	WaitForVirtualLocks(heaplocktag, ShareLock);
 
 	/*
 	 * At this moment we are sure that there are no transactions with the
@@ -693,27 +680,13 @@ 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);
+	/* 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
@@ -737,13 +710,7 @@ 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++;
-	}
+	WaitForVirtualLocks(heaplocktag, ShareLock);
 
 	/*
 	 * Now take the "reference snapshot" that will be used by validate_index()
@@ -772,74 +739,9 @@ 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.
+	 * transactions that might have older snapshots.
 	 */
-	old_snapshots = GetCurrentVirtualXIDs(snapshot->xmin, 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(snapshot->xmin,
-													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);
-	}
+	WaitForOldSnapshots(snapshot);
 
 	/*
 	 * Index can now be marked valid -- update its pg_index entry
@@ -852,7 +754,7 @@ DefineIndex(IndexStmt *stmt,
 	 * relcache inval on the parent table to force replanning of cached plans.
 	 * Otherwise existing sessions might fail to use the new index where it
 	 * would be useful.  (Note that our earlier commits did not create reasons
-	 * to replan; so relcache flush on the index itself was sufficient.)
+	 * to replan; relcache flush on the index itself was sufficient.)
 	 */
 	CacheInvalidateRelcacheByRelid(heaprelid.relId);
 
@@ -872,6 +774,526 @@ DefineIndex(IndexStmt *stmt,
 
 
 /*
+ * 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;
+
+	/*
+	 * 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:
+			{
+				/*
+				 * 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:
+			/* nothing to do */
+			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 each session lock separate transaction */
+	StartTransactionCommand();
+	foreach(lc, lockTags)
+	{
+		LOCKTAG	*localTag = (LOCKTAG *) lfirst(lc);
+		Assert(localTag && localTag->locktag_field2 != InvalidOid);
+		WaitForVirtualLocks(*localTag, ShareLock);
+	}
+	CommitTransactionCommand();
+
+	/* Get the first element of concurrent index list */
+	lc2 = list_head(concurrentIndexIds);
+
+	foreach(lc, indexIds)
+	{
+		Relation	indexRel;
+		Oid			indOid = lfirst_oid(lc);
+		Oid			concurrentOid = lfirst_oid(lc2);
+		bool		primary;
+
+		/* Move to next concurrent item */
+		lc2 = lnext(lc2);
+
+		/* 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);
+
+		/* 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 and are marked as valid once done.
+	 *
+	 * 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 scan of each concurrent index with the heap, then insert
+	 * any missing index entries.
+	 */
+	foreach(lc, concurrentIndexIds)
+	{
+		Oid indOid = lfirst_oid(lc);
+		Oid relOid;
+
+		/* 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);
+
+		/*
+		 * Concurrent index can now be marked as valid -- update pg_index
+		 * entries.
+		 */
+		index_set_state_flags(indOid, INDEX_CREATE_SET_VALID);
+
+		/*
+		 * 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(snapshot);
+
+		/*
+		 * The pg_index update will cause backends to update its entries for the
+		 * concurrent index but it is necessary to do the same thing for cache.
+		 */
+		CacheInvalidateRelcacheByRelid(relOid);
+
+		/* we can now do away with our active snapshot */
+		PopActiveSnapshot();
+
+		/* And we can remove the validating snapshot too */
+		UnregisterSnapshot(snapshot);
+
+		/* 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 old
+	 * index is marked as invalid once this is done, making it not usable
+	 * by other backends once its associated transaction is committed.
+	 */
+
+	/* Get the first element is concurrent index list */
+	lc2 = list_head(concurrentIndexIds);
+
+	/* Swap and mark all the indexes involved in the relation */
+	foreach(lc, indexIds)
+	{
+		Oid			indOid = lfirst_oid(lc);
+		Oid			concurrentOid = lfirst_oid(lc2);
+		Relation	indexRel, indexParentRel;
+
+		/* Move to next concurrent item */
+		lc2 = lnext(lc2);
+
+		/*
+		 * 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, ShareUpdateExclusiveLock);
+		indexParentRel = heap_open(indexRel->rd_index->indrelid,
+								   ShareUpdateExclusiveLock);
+
+		/* Mark the old index as invalid */
+		index_concurrent_clear_valid(indexParentRel, indOid);
+
+		/* Swap old index and its concurrent */
+		index_concurrent_swap(concurrentOid, indOid);
+
+		/*
+		 * 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, ShareUpdateExclusiveLock);
+		heap_close(indexParentRel, ShareUpdateExclusiveLock);
+
+		/* Commit this transaction and make old index invalidation visible */
+		CommitTransactionCommand();
+	}
+
+	/*
+	 * Phase 5 of REINDEX CONCURRENTLY
+	 *
+	 * The old indexes need to be marked as not ready. We need also to wait for
+	 * transactions that might use them. Each operation is performed with a
+	 * separate transaction.
+	 */
+
+	/* Mark the old indexes as not ready */
+	foreach(lc, indexIds)
+	{
+		Oid			indOid = lfirst_oid(lc);
+		Oid			relOid;
+
+		StartTransactionCommand();
+		relOid = IndexGetRelation(indOid, false);
+
+		/*
+		 * Finish the index invalidation and set it as dead. It is not
+		 * necessary to wait for virtual locks on the parent relation as it
+		 * is already sure that this session holds sufficient locks.s
+		 */
+		index_concurrent_set_dead(indOid, relOid, NULL);
+
+		/* Commit this transaction to make the update visible. */
+		CommitTransactionCommand();
+	}
+
+	/*
+	 * Phase 6 of REINDEX CONCURRENTLY
+	 *
+	 * Drop the old 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, indexIds)
+	{
+		Oid indexOid = lfirst_oid(lc);
+
+		/* 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);
+
+		/*
+		 * For the last index to be treated, do not commit transaction yet.
+		 * This will be done once all the locks on indexes and parent relations
+		 * are released.
+		 */
+		if (indexOid != llast_oid(indexIds))
+		{
+			/* 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);
+	}
+
+	return true;
+}
+
+
+/*
  * CheckMutability
  *		Test whether given expression is mutable
  */
@@ -1534,7 +1956,8 @@ ChooseRelationName(const char *name1, const char *name2,
 static char *
 ChooseIndexName(const char *tabname, Oid namespaceId,
 				List *colnames, List *exclusionOpNames,
-				bool primary, bool isconstraint)
+				bool primary, bool isconstraint,
+				bool concurrent)
 {
 	char	   *indexname;
 
@@ -1560,6 +1983,13 @@ ChooseIndexName(const char *tabname, Oid namespaceId,
 									   "key",
 									   namespaceId);
 	}
+	else if (concurrent)
+	{
+		indexname = ChooseRelationName(tabname,
+									   NULL,
+									   "cct",
+									   namespaceId);
+	}
 	else
 	{
 		indexname = ChooseRelationName(tabname,
@@ -1672,18 +2102,22 @@ ChooseIndexColumnNames(List *indexElems)
  *		Recreate a specific index.
  */
 Oid
-ReindexIndex(RangeVar *indexRelation)
+ReindexIndex(RangeVar *indexRelation, bool concurrent)
 {
 	Oid			indOid;
 	Oid			heapOid = InvalidOid;
 
-	/* lock level used here should match index lock reindex_index() */
-	indOid = RangeVarGetRelidExtended(indexRelation, AccessExclusiveLock,
-									  false, false,
-									  RangeVarCallbackForReindexIndex,
-									  (void *) &heapOid);
+	indOid = RangeVarGetRelidExtended(indexRelation,
+				concurrent ? ShareUpdateExclusiveLock : AccessExclusiveLock,
+				false, false,
+				RangeVarCallbackForReindexIndex,
+				(void *) &heapOid);
 
-	reindex_index(indOid, false);
+	/* Continue process for concurrent or non-concurrent case */
+	if (!concurrent)
+		reindex_index(indOid, false);
+	else
+		ReindexRelationConcurrently(indOid);
 
 	return indOid;
 }
@@ -1747,18 +2181,30 @@ RangeVarCallbackForReindexIndex(const RangeVar *relation,
 	}
 }
 
+
 /*
  * ReindexTable
  *		Recreate all indexes of a table (and of its toast table, if any)
  */
 Oid
-ReindexTable(RangeVar *relation)
+ReindexTable(RangeVar *relation, bool concurrent)
 {
 	Oid			heapOid;
 
 	/* The lock level used here should match reindex_relation(). */
-	heapOid = RangeVarGetRelidExtended(relation, ShareLock, false, false,
-									   RangeVarCallbackOwnsTable, NULL);
+	heapOid = RangeVarGetRelidExtended(relation,
+		concurrent ? ShareUpdateExclusiveLock : ShareLock,
+		false, false,
+		RangeVarCallbackOwnsTable, NULL);
+
+	/* Run through the concurrent process if necessary */
+	if (concurrent && !ReindexRelationConcurrently(heapOid))
+	{
+		ereport(NOTICE,
+				(errmsg("table \"%s\" has no indexes",
+						relation->relname)));
+		return heapOid;
+	}
 
 	if (!reindex_relation(heapOid, REINDEX_REL_PROCESS_TOAST))
 		ereport(NOTICE,
@@ -1777,7 +2223,10 @@ 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)
+ReindexDatabase(const char *databaseName,
+				bool do_system,
+				bool do_user,
+				bool concurrent)
 {
 	Relation	relationRelation;
 	HeapScanDesc scan;
@@ -1789,6 +2238,15 @@ ReindexDatabase(const char *databaseName, bool do_system, bool do_user)
 
 	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),
@@ -1871,15 +2329,40 @@ ReindexDatabase(const char *databaseName, bool do_system, bool do_user)
 	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());
-		if (reindex_relation(relid, REINDEX_REL_PROCESS_TOAST))
+
+		/* 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",
+					(errmsg("table \"%s.%s\" was reindexed%s",
 							get_namespace_name(get_rel_namespace(relid)),
-							get_rel_name(relid))));
+							get_rel_name(relid),
+							process_concurrent ? " concurrently" : "")));
 		PopActiveSnapshot();
 		CommitTransactionCommand();
 	}
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index eeddd9a..36bd576 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -891,6 +891,36 @@ RangeVarCallbackForDropRelation(const RangeVar *rel, Oid relOid, Oid oldRelOid,
 	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.
+	 */
+	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()))
diff --git a/src/backend/executor/execUtils.c b/src/backend/executor/execUtils.c
index 11be62e..1890766 100644
--- a/src/backend/executor/execUtils.c
+++ b/src/backend/executor/execUtils.c
@@ -1185,6 +1185,20 @@ check_exclusion_constraint(Relation heap, Relation index, IndexInfo *indexInfo,
 	}
 
 	/*
+	 * 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;
+
+	/*
 	 * Search the tuples that are in the index for any violations, including
 	 * tuples that aren't visible yet.
 	 */
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 2da08d1..b9cd66b 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -3602,6 +3602,7 @@ _copyReindexStmt(const ReindexStmt *from)
 	COPY_STRING_FIELD(name);
 	COPY_SCALAR_FIELD(do_system);
 	COPY_SCALAR_FIELD(do_user);
+	COPY_SCALAR_FIELD(concurrent);
 
 	return newnode;
 }
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 9e313c8..c7a5345 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -1841,6 +1841,7 @@ _equalReindexStmt(const ReindexStmt *a, const ReindexStmt *b)
 	COMPARE_STRING_FIELD(name);
 	COMPARE_SCALAR_FIELD(do_system);
 	COMPARE_SCALAR_FIELD(do_user);
+	COMPARE_SCALAR_FIELD(concurrent);
 
 	return true;
 }
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 342b796..60a6c96 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -6672,29 +6672,32 @@ opt_if_exists: IF_P EXISTS						{ $$ = TRUE; }
  *****************************************************************************/
 
 ReindexStmt:
-			REINDEX reindex_type qualified_name opt_force
+			REINDEX reindex_type opt_concurrently qualified_name opt_force
 				{
 					ReindexStmt *n = makeNode(ReindexStmt);
 					n->kind = $2;
-					n->relation = $3;
+					n->concurrent = $3;
+					n->relation = $4;
 					n->name = NULL;
 					$$ = (Node *)n;
 				}
-			| REINDEX SYSTEM_P name opt_force
+			| REINDEX SYSTEM_P opt_concurrently name opt_force
 				{
 					ReindexStmt *n = makeNode(ReindexStmt);
 					n->kind = OBJECT_DATABASE;
-					n->name = $3;
+					n->concurrent = $3;
+					n->name = $4;
 					n->relation = NULL;
 					n->do_system = true;
 					n->do_user = false;
 					$$ = (Node *)n;
 				}
-			| REINDEX DATABASE name opt_force
+			| REINDEX DATABASE opt_concurrently name opt_force
 				{
 					ReindexStmt *n = makeNode(ReindexStmt);
 					n->kind = OBJECT_DATABASE;
-					n->name = $3;
+					n->concurrent = $3;
+					n->name = $4;
 					n->relation = NULL;
 					n->do_system = true;
 					n->do_user = true;
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index 4308128..b5d8cc0 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -2528,6 +2528,117 @@ XidCacheRemoveRunningXids(TransactionId xid,
 	LWLockRelease(ProcArrayLock);
 }
 
+
+/*
+ * WaitForVirtualLocks
+ *
+ * Wait until no transaction hold the relation related to lock this lock.
+ * To do this, inquire which xacts currently would conflict with this lock on
+ * the table referred by the 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
+WaitForVirtualLocks(LOCKTAG heaplocktag, LOCKMODE lockmode)
+{
+	VirtualTransactionId *old_lockholders;
+
+	old_lockholders = GetLockConflicts(&heaplocktag, lockmode);
+
+	while (VirtualTransactionIdIsValid(*old_lockholders))
+	{
+		VirtualXactLock(*old_lockholders, true);
+		old_lockholders++;
+	}
+}
+
+
+/*
+ * WaitForOldSnapshots
+ *
+ * Wait for transactions that might have older snapshot than the given one,
+ * because is 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 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.
+ */
+void
+WaitForOldSnapshots(Snapshot snapshot)
+{
+	int i, n_old_snapshots;
+	VirtualTransactionId *old_snapshots;
+
+	old_snapshots = GetCurrentVirtualXIDs(snapshot->xmin, 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(snapshot->xmin,
+													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
 
 /*
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 8904c6f..7360dda 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -1282,15 +1282,19 @@ standard_ProcessUtility(Node *parsetree,
 			{
 				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);
+						ReindexIndex(stmt->relation, stmt->concurrent);
 						break;
 					case OBJECT_TABLE:
-						ReindexTable(stmt->relation);
+						ReindexTable(stmt->relation, stmt->concurrent);
 						break;
 					case OBJECT_DATABASE:
 
@@ -1302,8 +1306,8 @@ standard_ProcessUtility(Node *parsetree,
 						 */
 						PreventTransactionChain(isTopLevel,
 												"REINDEX DATABASE");
-						ReindexDatabase(stmt->name,
-										stmt->do_system, stmt->do_user);
+						ReindexDatabase(stmt->name, stmt->do_system,
+										stmt->do_user, stmt->concurrent);
 						break;
 					default:
 						elog(ERROR, "unrecognized object type: %d",
diff --git a/src/include/catalog/index.h b/src/include/catalog/index.h
index fb323f7..bbad5fe 100644
--- a/src/include/catalog/index.h
+++ b/src/include/catalog/index.h
@@ -60,7 +60,26 @@ extern Oid index_create(Relation heapRelation,
 			 bool allow_system_table_mods,
 			 bool skip_build,
 			 bool concurrent,
-			 bool is_internal);
+			 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);
+
+extern void index_concurrent_drop(Oid indexOid);
 
 extern void index_constraint_create(Relation heapRelation,
 						Oid indexRelationId,
@@ -88,7 +107,8 @@ extern void index_build(Relation heapRelation,
 			Relation indexRelation,
 			IndexInfo *indexInfo,
 			bool isprimary,
-			bool isreindex);
+			bool isreindex,
+			bool istoastupdate);
 
 extern double IndexBuildHeapScan(Relation heapRelation,
 				   Relation indexRelation,
diff --git a/src/include/catalog/indexing.h b/src/include/catalog/indexing.h
index 6251fb8..3555b14 100644
--- a/src/include/catalog/indexing.h
+++ b/src/include/catalog/indexing.h
@@ -123,6 +123,9 @@ DECLARE_INDEX(pg_constraint_contypid_index, 2666, on pg_constraint using btree(c
 #define ConstraintTypidIndexId	2666
 DECLARE_UNIQUE_INDEX(pg_constraint_oid_index, 2667, on pg_constraint using btree(oid oid_ops));
 #define ConstraintOidIndexId  2667
+/* This following index is not used for a cache and is not unique */
+DECLARE_INDEX(pg_constraint_confrelid_index, 3086, on pg_constraint using btree(confrelid oid_ops));
+#define ConstraintForeignRelidIndexId	3086
 
 DECLARE_UNIQUE_INDEX(pg_conversion_default_index, 2668, on pg_conversion using btree(connamespace oid_ops, conforencoding int4_ops, contoencoding int4_ops, oid oid_ops));
 #define ConversionDefaultIndexId  2668
diff --git a/src/include/catalog/pg_constraint.h b/src/include/catalog/pg_constraint.h
index 29f71f1..a37d39a 100644
--- a/src/include/catalog/pg_constraint.h
+++ b/src/include/catalog/pg_constraint.h
@@ -254,4 +254,8 @@ extern bool check_functional_grouping(Oid relid,
 						  List *grouping_columns,
 						  List **constraintDeps);
 
+extern void switchIndexConstraintOnForeignKey(Oid parentOid,
+											  Oid oldIndexOid,
+											  Oid newIndexOid);
+
 #endif   /* PG_CONSTRAINT_H */
diff --git a/src/include/commands/defrem.h b/src/include/commands/defrem.h
index 62515b2..54137c6 100644
--- a/src/include/commands/defrem.h
+++ b/src/include/commands/defrem.h
@@ -26,10 +26,11 @@ 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 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 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,
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index d8678e5..e5377b4 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -2521,6 +2521,7 @@ typedef struct ReindexStmt
 	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;
 
 /* ----------------------
diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h
index d5fdfea..0b591ce 100644
--- a/src/include/storage/procarray.h
+++ b/src/include/storage/procarray.h
@@ -76,4 +76,7 @@ extern void XidCacheRemoveRunningXids(TransactionId xid,
 						  int nxids, const TransactionId *xids,
 						  TransactionId latestXid);
 
+extern void WaitForVirtualLocks(LOCKTAG heaplocktag, LOCKMODE lockmode);
+extern void WaitForOldSnapshots(Snapshot snapshot);
+
 #endif   /* PROCARRAY_H */
diff --git a/src/test/regress/expected/create_index.out b/src/test/regress/expected/create_index.out
index 2ae991e..d03a1f6 100644
--- a/src/test/regress/expected/create_index.out
+++ b/src/test/regress/expected/create_index.out
@@ -2721,3 +2721,46 @@ ORDER BY thousand;
         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
+CREATE UNIQUE INDEX concur_reindex_ind1 ON concur_reindex_tab(c1);
+CREATE INDEX concur_reindex_ind2 ON concur_reindex_tab(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');
+REINDEX INDEX CONCURRENTLY concur_reindex_ind1;
+REINDEX TABLE CONCURRENTLY concur_reindex_tab;
+-- 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_ind2" btree (c2)
+Referenced by:
+    TABLE "concur_reindex_tab2" CONSTRAINT "concur_reindex_tab2_c1_fkey" FOREIGN KEY (c1) REFERENCES concur_reindex_tab(c1)
+
+DROP TABLE concur_reindex_tab, concur_reindex_tab2;
diff --git a/src/test/regress/sql/create_index.sql b/src/test/regress/sql/create_index.sql
index 914e7a5..91ee74e 100644
--- a/src/test/regress/sql/create_index.sql
+++ b/src/test/regress/sql/create_index.sql
@@ -912,3 +912,33 @@ ORDER BY thousand;
 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
+CREATE UNIQUE INDEX concur_reindex_ind1 ON concur_reindex_tab(c1);
+CREATE INDEX concur_reindex_ind2 ON concur_reindex_tab(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');
+REINDEX INDEX CONCURRENTLY concur_reindex_ind1;
+REINDEX TABLE CONCURRENTLY concur_reindex_tab;
+
+-- 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 TABLE concur_reindex_tab, concur_reindex_tab2;