brin-autosummarize.patch

diff --git a/doc/src/sgml/brin.sgml b/doc/src/sgml/brin.sgml
index 6448b18..480895b 100644
--- a/doc/src/sgml/brin.sgml
+++ b/doc/src/sgml/brin.sgml
@@ -74,9 +74,13 @@
    tuple; those tuples remain unsummarized until a summarization run is
    invoked later, creating initial summaries.
    This process can be invoked manually using the
-   <function>brin_summarize_new_values(regclass)</function> function,
-   or automatically when <command>VACUUM</command> processes the table.
+   <function>brin_summarize_new_values(regclass)</function> function;
+   automatically when <command>VACUUM</command> processes the table;
+   or by automatic summarization executed by autovacuum, as insertions
+   occur.  (This last trigger is disabled by default and is enabled with
+   the parameter <literal>autosummarize</literal>.)
   </para>
+
  </sect2>
 </sect1>
 
diff --git a/doc/src/sgml/ref/create_index.sgml b/doc/src/sgml/ref/create_index.sgml
index fcb7a60..80d9c39 100644
--- a/doc/src/sgml/ref/create_index.sgml
+++ b/doc/src/sgml/ref/create_index.sgml
@@ -382,7 +382,7 @@ CREATE [ UNIQUE ] INDEX [ CONCURRENTLY ] [ [ IF NOT EXISTS ] <replaceable class=
    </variablelist>
 
    <para>
-    <acronym>BRIN</> indexes accept a different parameter:
+    <acronym>BRIN</> indexes accept different parameters:
    </para>
 
    <variablelist>
@@ -396,6 +396,16 @@ CREATE [ UNIQUE ] INDEX [ CONCURRENTLY ] [ [ IF NOT EXISTS ] <replaceable class=
     </para>
     </listitem>
    </varlistentry>
+
+   <varlistentry>
+    <term><literal>autosummarize</></term>
+    <listitem>
+    <para>
+     Defines whether a summarization run is invoked for the previous page
+     range whenever an insertion is detected on the next one.
+    </para>
+    </listitem>
+   </varlistentry>
    </variablelist>
   </refsect2>
 
diff --git a/src/backend/access/brin/brin.c b/src/backend/access/brin/brin.c
index b22563b..01586ff 100644
--- a/src/backend/access/brin/brin.c
+++ b/src/backend/access/brin/brin.c
@@ -26,6 +26,7 @@
 #include "catalog/pg_am.h"
 #include "miscadmin.h"
 #include "pgstat.h"
+#include "postmaster/autovacuum.h"
 #include "storage/bufmgr.h"
 #include "storage/freespace.h"
 #include "utils/builtins.h"
@@ -60,10 +61,12 @@ typedef struct BrinOpaque
 	BrinDesc   *bo_bdesc;
 } BrinOpaque;
 
+#define BRIN_ALL_BLOCKRANGES	InvalidBlockNumber
+
 static BrinBuildState *initialize_brin_buildstate(Relation idxRel,
 						   BrinRevmap *revmap, BlockNumber pagesPerRange);
 static void terminate_brin_buildstate(BrinBuildState *state);
-static void brinsummarize(Relation index, Relation heapRel,
+static void brinsummarize(Relation index, Relation heapRel, BlockNumber pageRange,
 			  double *numSummarized, double *numExisting);
 static void form_and_insert_tuple(BrinBuildState *state);
 static void union_tuples(BrinDesc *bdesc, BrinMemTuple *a,
@@ -126,8 +129,11 @@ brinhandler(PG_FUNCTION_ARGS)
  * with those of the new tuple.  If the tuple values are not consistent with
  * the summary tuple, we need to update the index tuple.
  *
+ * If autosummarization is enabled, check if we need to summarize the previous
+ * page range.
+ *
  * If the range is not currently summarized (i.e. the revmap returns NULL for
- * it), there's nothing to do.
+ * it), there's nothing to do for this tuple.
  */
 bool
 brininsert(Relation idxRel, Datum *values, bool *nulls,
@@ -141,6 +147,7 @@ brininsert(Relation idxRel, Datum *values, bool *nulls,
 	Buffer		buf = InvalidBuffer;
 	MemoryContext tupcxt = NULL;
 	MemoryContext oldcxt = CurrentMemoryContext;
+	bool		autosummarize = BrinGetAutoSummarize(idxRel);
 
 	revmap = brinRevmapInitialize(idxRel, &pagesPerRange, NULL);
 
@@ -148,18 +155,41 @@ brininsert(Relation idxRel, Datum *values, bool *nulls,
 	{
 		bool		need_insert = false;
 		OffsetNumber off;
-		BrinTuple  *brtup;
+		BrinTuple  *brtup = NULL;
 		BrinMemTuple *dtup;
 		BlockNumber heapBlk;
+		BlockNumber heapBlk0;
 		int			keyno;
 
 		CHECK_FOR_INTERRUPTS();
 
 		heapBlk = ItemPointerGetBlockNumber(heaptid);
 		/* normalize the block number to be the first block in the range */
-		heapBlk = (heapBlk / pagesPerRange) * pagesPerRange;
-		brtup = brinGetTupleForHeapBlock(revmap, heapBlk, &buf, &off, NULL,
-										 BUFFER_LOCK_SHARE, NULL);
+		heapBlk0 = (heapBlk / pagesPerRange) * pagesPerRange;
+
+		/*
+		 * If auto-summarization is enabled and we just inserted the first
+		 * tuple into the first block of a new page range, request a
+		 * summarization run.
+		 */
+		if (autosummarize &&
+			heapBlk == heapBlk0 &&
+			ItemPointerGetOffsetNumber(heaptid) == FirstOffsetNumber)
+		{
+			BlockNumber lastPageRange = heapBlk0;
+
+			if (heapBlk0 >= pagesPerRange)
+				lastPageRange -= pagesPerRange;
+			brtup = brinGetTupleForHeapBlock(revmap, lastPageRange, &buf, &off, NULL,
+											 BUFFER_LOCK_SHARE, NULL);
+			if (!brtup)
+				AutoVacuumRequestWork(AVW_BRINSummarizeRange,
+									  RelationGetRelid(idxRel));
+		}
+
+		if (!brtup)
+			brtup = brinGetTupleForHeapBlock(revmap, heapBlk0, &buf, &off,
+											 NULL, BUFFER_LOCK_SHARE, NULL);
 
 		/* if range is unsummarized, there's nothing to do */
 		if (!brtup)
@@ -747,7 +777,7 @@ brinvacuumcleanup(IndexVacuumInfo *info, IndexBulkDeleteResult *stats)
 
 	brin_vacuum_scan(info->index, info->strategy);
 
-	brinsummarize(info->index, heapRel,
+	brinsummarize(info->index, heapRel, BRIN_ALL_BLOCKRANGES,
 				  &stats->num_index_tuples, &stats->num_index_tuples);
 
 	heap_close(heapRel, AccessShareLock);
@@ -765,7 +795,8 @@ brinoptions(Datum reloptions, bool validate)
 	BrinOptions *rdopts;
 	int			numoptions;
 	static const relopt_parse_elt tab[] = {
-		{"pages_per_range", RELOPT_TYPE_INT, offsetof(BrinOptions, pagesPerRange)}
+		{"pages_per_range", RELOPT_TYPE_INT, offsetof(BrinOptions, pagesPerRange)},
+		{"autosummarize", RELOPT_TYPE_BOOL, offsetof(BrinOptions, autosummarize)}
 	};
 
 	options = parseRelOptions(reloptions, validate, RELOPT_KIND_BRIN,
@@ -837,7 +868,7 @@ brin_summarize_new_values(PG_FUNCTION_ARGS)
 						RelationGetRelationName(indexRel))));
 
 	/* OK, do it */
-	brinsummarize(indexRel, heapRel, &numSummarized, NULL);
+	brinsummarize(indexRel, heapRel, BRIN_ALL_BLOCKRANGES, &numSummarized, NULL);
 
 	relation_close(indexRel, ShareUpdateExclusiveLock);
 	relation_close(heapRel, ShareUpdateExclusiveLock);
@@ -1063,17 +1094,17 @@ summarize_range(IndexInfo *indexInfo, BrinBuildState *state, Relation heapRel,
 }
 
 /*
- * Scan a complete BRIN index, and summarize each page range that's not already
- * summarized.  The index and heap must have been locked by caller in at
- * least ShareUpdateExclusiveLock mode.
+ * Scan a portion of a BRIN index, and summarize each page range that's not
+ * already summarized.  The index and heap must have been locked by caller in
+ * at least ShareUpdateExclusiveLock mode.
  *
  * For each new index tuple inserted, *numSummarized (if not NULL) is
  * incremented; for each existing tuple, *numExisting (if not NULL) is
  * incremented.
  */
 static void
-brinsummarize(Relation index, Relation heapRel, double *numSummarized,
-			  double *numExisting)
+brinsummarize(Relation index, Relation heapRel, BlockNumber pageRange,
+			  double *numSummarized, double *numExisting)
 {
 	BrinRevmap *revmap;
 	BrinBuildState *state = NULL;
@@ -1082,6 +1113,8 @@ brinsummarize(Relation index, Relation heapRel, double *numSummarized,
 	BlockNumber heapBlk;
 	BlockNumber pagesPerRange;
 	Buffer		buf;
+	BlockNumber startBlk;
+	BlockNumber endBlk;
 
 	revmap = brinRevmapInitialize(index, &pagesPerRange, NULL);
 
@@ -1090,7 +1123,20 @@ brinsummarize(Relation index, Relation heapRel, double *numSummarized,
 	 */
 	buf = InvalidBuffer;
 	heapNumBlocks = RelationGetNumberOfBlocks(heapRel);
-	for (heapBlk = 0; heapBlk < heapNumBlocks; heapBlk += pagesPerRange)
+	if (pageRange == BRIN_ALL_BLOCKRANGES ||
+		pageRange > heapNumBlocks)
+	{
+		startBlk = 0;
+		endBlk = heapNumBlocks;
+	}
+	else
+	{
+		startBlk = pageRange;
+		endBlk = startBlk + pagesPerRange;
+		if (endBlk > heapNumBlocks)
+			endBlk = heapNumBlocks - 1;
+	}
+	for (heapBlk = startBlk; heapBlk < endBlk; heapBlk += pagesPerRange)
 	{
 		BrinTuple  *tup;
 		OffsetNumber off;
diff --git a/src/backend/access/brin/brin_revmap.c b/src/backend/access/brin/brin_revmap.c
index 0de6999..5d45b48 100644
--- a/src/backend/access/brin/brin_revmap.c
+++ b/src/backend/access/brin/brin_revmap.c
@@ -205,7 +205,11 @@ brinGetTupleForHeapBlock(BrinRevmap *revmap, BlockNumber heapBlk,
 	/* normalize the heap block number to be the first page in the range */
 	heapBlk = (heapBlk / revmap->rm_pagesPerRange) * revmap->rm_pagesPerRange;
 
-	/* Compute the revmap page number we need */
+	/*
+	 * Compute the revmap page number we need.  If Invalid is returned (i.e.,
+	 * the revmap page hasn't been created yet), the requested page range is
+	 * not summarized.
+	 */
 	mapBlk = revmap_get_blkno(revmap, heapBlk);
 	if (mapBlk == InvalidBlockNumber)
 	{
diff --git a/src/backend/access/common/reloptions.c b/src/backend/access/common/reloptions.c
index 42b4ea4..66b493c 100644
--- a/src/backend/access/common/reloptions.c
+++ b/src/backend/access/common/reloptions.c
@@ -58,6 +58,15 @@ static relopt_bool boolRelOpts[] =
 {
 	{
 		{
+			"autosummarize",
+			"Enables automatic summarization on this BRIN index",
+			RELOPT_KIND_BRIN,
+			AccessExclusiveLock
+		},
+		false
+	},
+	{
+		{
 			"autovacuum_enabled",
 			"Enables autovacuum in this relation",
 			RELOPT_KIND_HEAP | RELOPT_KIND_TOAST,
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index e8de9a3..c9853a9 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -92,7 +92,9 @@
 #include "storage/procsignal.h"
 #include "storage/sinvaladt.h"
 #include "tcop/tcopprot.h"
+#include "utils/dsa.h"
 #include "utils/fmgroids.h"
+#include "utils/fmgrprotos.h"
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/ps_status.h"
@@ -252,9 +254,10 @@ typedef enum
  * av_runningWorkers the WorkerInfo non-free queue
  * av_startingWorker pointer to WorkerInfo currently being started (cleared by
  *					the worker itself as soon as it's up and running)
+ * av_dsa_handle	handle for allocatable shared memory
  *
  * This struct is protected by AutovacuumLock, except for av_signal and parts
- * of the worker list (see above).
+ * of the worker list (see above).  av_dsa_handle is readable unlocked.
  *-------------
  */
 typedef struct
@@ -264,6 +267,8 @@ typedef struct
 	dlist_head	av_freeWorkers;
 	dlist_head	av_runningWorkers;
 	WorkerInfo	av_startingWorker;
+	dsa_handle	av_dsa_handle;
+	dsa_pointer	av_workitems;
 } AutoVacuumShmemStruct;
 
 static AutoVacuumShmemStruct *AutoVacuumShmem;
@@ -278,6 +283,30 @@ static MemoryContext DatabaseListCxt = NULL;
 /* Pointer to my own WorkerInfo, valid on each worker */
 static WorkerInfo MyWorkerInfo = NULL;
 
+/*
+ * Autovacuum workitem array, stored in AutoVacuumShmem->av_workitems.  This
+ * list is mostly protected by AutovacuumLock, except that an autovacuum
+ * worker may "claim" an item (by marking it active), and then no other process
+ * is allowed to touch it.
+ */
+typedef struct AutoVacuumWorkItem
+{
+	AutoVacuumWorkItemType avw_type;
+	Oid			avw_database;
+	Oid			avw_relation;
+	bool		avw_active;
+	dsa_pointer	avw_next;
+} AutoVacuumWorkItem;
+
+#define NUM_WORKITEMS	256
+typedef struct
+{
+	dsa_pointer		avs_usedItems;
+	dsa_pointer		avs_freeItems;
+} AutovacWorkItems;
+
+static dsa_area	*AutoVacuumDSA = NULL;
+
 /* PID of launcher, valid only in worker while shutting down */
 int			AutovacuumLauncherPid = 0;
 
@@ -316,6 +345,7 @@ static AutoVacOpts *extract_autovac_opts(HeapTuple tup,
 static PgStat_StatTabEntry *get_pgstat_tabentry_relid(Oid relid, bool isshared,
 						  PgStat_StatDBEntry *shared,
 						  PgStat_StatDBEntry *dbentry);
+static void perform_work_item(AutoVacuumWorkItem *workitem);
 static void autovac_report_activity(autovac_table *tab);
 static void av_sighup_handler(SIGNAL_ARGS);
 static void avl_sigusr2_handler(SIGNAL_ARGS);
@@ -574,6 +604,22 @@ AutoVacLauncherMain(int argc, char *argv[])
 	 */
 	rebuild_database_list(InvalidOid);
 
+	/*
+	 * Set up our DSA so that backends can install work-item requests.  It may
+	 * already exist as created by a previous launcher.
+	 */
+	if (!AutoVacuumShmem->av_dsa_handle)
+	{
+		LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);
+		AutoVacuumDSA = dsa_create(LWTRANCHE_AUTOVACUUM);
+		AutoVacuumShmem->av_dsa_handle = dsa_get_handle(AutoVacuumDSA);
+		/* delay array allocation until first request */
+		AutoVacuumShmem->av_workitems = InvalidDsaPointer;
+		LWLockRelease(AutovacuumLock);
+	}
+	else
+		AutoVacuumDSA = dsa_attach(AutoVacuumShmem->av_dsa_handle);
+
 	/* loop until shutdown request */
 	while (!got_SIGTERM)
 	{
@@ -1617,6 +1663,13 @@ AutoVacWorkerMain(int argc, char *argv[])
 	{
 		char		dbname[NAMEDATALEN];
 
+		if (AutoVacuumShmem->av_dsa_handle)
+		{
+			/* First use of DSA in this worker, so attach to it */
+			Assert(!AutoVacuumDSA);
+			AutoVacuumDSA = dsa_attach(AutoVacuumShmem->av_dsa_handle);
+		}
+
 		/*
 		 * Report autovac startup to the stats collector.  We deliberately do
 		 * this before InitPostgres, so that the last_autovac_time will get
@@ -2467,6 +2520,69 @@ deleted:
 	}
 
 	/*
+	 * Perform additional work items, as requested by backends.
+	 */
+	if (AutoVacuumShmem->av_workitems)
+	{
+		dsa_pointer		nextitem;
+		AutovacWorkItems *workitems;
+
+		LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);
+
+		/*
+		 * Scan the list of pending items, and process the inactive ones in our
+		 * database.
+		 */
+		workitems = (AutovacWorkItems *)
+			dsa_get_address(AutoVacuumDSA, AutoVacuumShmem->av_workitems);
+		nextitem = workitems->avs_usedItems;
+
+		while (nextitem != InvalidDsaPointer)
+		{
+			AutoVacuumWorkItem	*workitem;
+
+			workitem = (AutoVacuumWorkItem *)
+				dsa_get_address(AutoVacuumDSA, nextitem);
+
+			if (workitem->avw_database == MyDatabaseId && !workitem->avw_active)
+			{
+				/* claim this one, and release lock while we process it */
+				workitem->avw_active = true;
+
+				LWLockRelease(AutovacuumLock);
+				perform_work_item(workitem);
+
+				/*
+				 * Check for config changes before acquiring lock for further
+				 * jobs.
+				 */
+				CHECK_FOR_INTERRUPTS();
+				if (got_SIGHUP)
+				{
+					got_SIGHUP = false;
+					ProcessConfigFile(PGC_SIGHUP);
+				}
+
+				LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);
+
+				/*
+				 * Remove the job we just completed from the used list and put
+				 * the array item back on the free list.
+				 */
+				workitems->avs_usedItems = workitem->avw_next;
+				workitem->avw_next = workitems->avs_freeItems;
+				workitems->avs_freeItems = nextitem;
+			}
+
+			/* prepare for next iteration */
+			nextitem = workitems->avs_usedItems;
+		}
+
+		/* all done */
+		LWLockRelease(AutovacuumLock);
+	}
+
+	/*
 	 * We leak table_toast_map here (among other things), but since we're
 	 * going away soon, it's not a problem.
 	 */
@@ -2498,6 +2614,101 @@ deleted:
 	CommitTransactionCommand();
 }
 
+static void
+perform_work_item(AutoVacuumWorkItem *workitem)
+{
+	char	   *cur_datname = NULL;
+	char	   *cur_nspname = NULL;
+	char	   *cur_relname = NULL;
+
+	elog(LOG, "performing work on relation %u", workitem->avw_relation);
+
+	/*
+	 * Note we do not store table info in MyWorkerInfo, since this is not
+	 * vacuuming proper.
+	 */
+
+	/*
+	 * Save the relation name for a possible error message, to avoid a
+	 * catalog lookup in case of an error.  If any of these return NULL,
+	 * then the relation has been dropped since last we checked; skip it.
+	 * Note: they must live in a long-lived memory context because we call
+	 * vacuum and analyze in different transactions.
+	 */
+
+	cur_relname = get_rel_name(workitem->avw_relation);
+	cur_nspname = get_namespace_name(get_rel_namespace(workitem->avw_relation));
+	cur_datname = get_database_name(MyDatabaseId);
+	if (!cur_relname || !cur_nspname || !cur_datname)
+		goto deleted2;
+
+	/*
+	 * We will abort the current work item if something errors out, and
+	 * continue with the next one; in particular, this happens if we are
+	 * interrupted with SIGINT.  XXX but the work item was already deleted
+	 * from the work list.  Maybe instead of this we should set a "being
+	 * processed" flag in the work item, move it to the back of the list,
+	 * and only delete if we're successful.
+	 */
+	PG_TRY();
+	{
+		/* have at it */
+		MemoryContextSwitchTo(TopTransactionContext);
+
+		switch (workitem->avw_type)
+		{
+			case AVW_BRINSummarizeRange:
+				DirectFunctionCall1(brin_summarize_new_values,
+									ObjectIdGetDatum(workitem->avw_relation));
+				break;
+			default:
+				elog(WARNING, "unrecognized work item found: type %d",
+					 workitem->avw_type);
+				break;
+		}
+
+		/*
+		 * Clear a possible query-cancel signal, to avoid a late reaction
+		 * to an automatically-sent signal because of vacuuming the
+		 * current table (we're done with it, so it would make no sense to
+		 * cancel at this point.)
+		 */
+		QueryCancelPending = false;
+	}
+	PG_CATCH();
+	{
+		/*
+		 * Abort the transaction, start a new one, and proceed with the
+		 * next table in our list.
+		 */
+		HOLD_INTERRUPTS();
+		errcontext("processing work entry for relation \"%s.%s.%s\"",
+				   cur_datname, cur_nspname, cur_relname);
+		EmitErrorReport();
+
+		/* this resets the PGXACT flags too */
+		AbortOutOfAnyTransaction();
+		FlushErrorState();
+		MemoryContextResetAndDeleteChildren(PortalContext);
+
+		/* restart our transaction for the following operations */
+		StartTransactionCommand();
+		RESUME_INTERRUPTS();
+	}
+	PG_END_TRY();
+
+	/* We intentionally do not set did_vacuum here */
+
+	/* be tidy */
+deleted2:
+	if (cur_datname)
+		pfree(cur_datname);
+	if (cur_nspname)
+		pfree(cur_nspname);
+	if (cur_relname)
+		pfree(cur_relname);
+}
+
 /*
  * extract_autovac_opts
  *
@@ -2959,6 +3170,119 @@ AutoVacuumingActive(void)
 }
 
 /*
+ * Request one work item to the next autovacuum run processing our database.
+ */
+void
+AutoVacuumRequestWork(AutoVacuumWorkItemType type, Oid relationId)
+{
+	AutovacWorkItems *workitems;
+	dsa_pointer		wi_ptr;
+	AutoVacuumWorkItem *workitem;
+
+	elog(LOG, "requesting work on relation %u", relationId);
+
+	LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);
+
+	/*
+	 * It may be useful to deduplicate the list upon insertion.  For the only
+	 * currently existing caller, this is not necessary.
+	 */
+
+	/* First use in this process?  Initialize DSA */
+	if (!AutoVacuumDSA)
+	{
+		if (!AutoVacuumShmem->av_dsa_handle)
+		{
+			/* autovacuum launcher not started; nothing can be done */
+			LWLockRelease(AutovacuumLock);
+			return;
+		}
+		AutoVacuumDSA = dsa_attach(AutoVacuumShmem->av_dsa_handle);
+
+		if (!AutoVacuumDSA)
+		{
+			/* cannot attach?  disregard request */
+			LWLockRelease(AutovacuumLock);
+			return;
+		}
+	}
+
+	/* First use overall?  Allocate work items array */
+	if (AutoVacuumShmem->av_workitems == InvalidDsaPointer)
+	{
+		int		i;
+		AutovacWorkItems *workitems;
+
+		AutoVacuumShmem->av_workitems =
+			dsa_allocate_extended(AutoVacuumDSA,
+								  sizeof(AutovacWorkItems) +
+								  NUM_WORKITEMS * sizeof(AutoVacuumWorkItem),
+								  DSA_ALLOC_NO_OOM);
+		/* if out of memory, silently disregard the request */
+		if (AutoVacuumShmem->av_workitems == InvalidDsaPointer)
+		{
+			dsa_detach(AutoVacuumDSA);
+			AutoVacuumDSA = NULL;
+			LWLockRelease(AutovacuumLock);
+			return;
+		}
+
+		/* Initialize each array entry as a member of the free list */
+		workitems = dsa_get_address(AutoVacuumDSA, AutoVacuumShmem->av_workitems);
+
+		workitems->avs_usedItems = InvalidDsaPointer;
+		workitems->avs_freeItems = InvalidDsaPointer;
+		for (i = 0; i < NUM_WORKITEMS; i++)
+		{
+			/* XXX surely there is a simpler way to do this */
+			wi_ptr = AutoVacuumShmem->av_workitems + sizeof(AutovacWorkItems) +
+				sizeof(AutoVacuumWorkItem) * i;
+			workitem = (AutoVacuumWorkItem *) dsa_get_address(AutoVacuumDSA, wi_ptr);
+
+			workitem->avw_type = 0;
+			workitem->avw_database = InvalidOid;
+			workitem->avw_relation = InvalidOid;
+			workitem->avw_active = false;
+
+			/* put this item in the free list */
+			workitem->avw_next = workitems->avs_freeItems;
+			workitems->avs_freeItems = wi_ptr;
+		}
+	}
+
+	workitems = (AutovacWorkItems *)
+		dsa_get_address(AutoVacuumDSA, AutoVacuumShmem->av_workitems);
+
+	/* If array is full, disregard the request */
+	if (workitems->avs_freeItems == InvalidDsaPointer)
+	{
+		LWLockRelease(AutovacuumLock);
+		dsa_detach(AutoVacuumDSA);
+		AutoVacuumDSA = NULL;
+		return;
+	}
+
+	/* remove workitem struct from free list ... */
+	wi_ptr = workitems->avs_freeItems;
+	workitem = dsa_get_address(AutoVacuumDSA, wi_ptr);
+	workitems->avs_freeItems = workitem->avw_next;
+
+	/* ... initialize it ... */
+	workitem->avw_type = type;
+	workitem->avw_database = MyDatabaseId;
+	workitem->avw_relation = relationId;
+	workitem->avw_active = false;
+	workitem->avw_next = workitems->avs_usedItems;
+
+	/* ... and put it on autovacuum's to-do list */
+	workitems->avs_usedItems = wi_ptr;
+
+	LWLockRelease(AutovacuumLock);
+	dsa_detach(AutoVacuumDSA);
+	AutoVacuumDSA = NULL;
+}
+
+/*
  * autovac_init
  *		This is called at postmaster initialization.
  *
diff --git a/src/backend/storage/ipc/dsm.c b/src/backend/storage/ipc/dsm.c
index 54378bc..b8c96db 100644
--- a/src/backend/storage/ipc/dsm.c
+++ b/src/backend/storage/ipc/dsm.c
@@ -1095,7 +1095,8 @@ dsm_create_descriptor(void)
 {
 	dsm_segment *seg;
 
-	ResourceOwnerEnlargeDSMs(CurrentResourceOwner);
+	if (CurrentResourceOwner)
+		ResourceOwnerEnlargeDSMs(CurrentResourceOwner);
 
 	seg = MemoryContextAlloc(TopMemoryContext, sizeof(dsm_segment));
 	dlist_push_head(&dsm_segment_list, &seg->node);
@@ -1106,8 +1107,11 @@ dsm_create_descriptor(void)
 	seg->mapped_address = NULL;
 	seg->mapped_size = 0;
 
-	seg->resowner = CurrentResourceOwner;
-	ResourceOwnerRememberDSM(CurrentResourceOwner, seg);
+	if (CurrentResourceOwner)
+	{
+		seg->resowner = CurrentResourceOwner;
+		ResourceOwnerRememberDSM(CurrentResourceOwner, seg);
+	}
 
 	slist_init(&seg->on_detach);
 
diff --git a/src/backend/utils/mmgr/dsa.c b/src/backend/utils/mmgr/dsa.c
index 49e68b4..6d5d12a 100644
--- a/src/backend/utils/mmgr/dsa.c
+++ b/src/backend/utils/mmgr/dsa.c
@@ -498,7 +498,7 @@ dsa_get_handle(dsa_area *area)
 
 /*
  * Attach to an area given a handle generated (possibly in another process) by
- * dsa_get_area_handle.  The area must have been created with dsa_create (not
+ * dsa_get_handle.  The area must have been created with dsa_create (not
  * dsa_create_in_place).
  */
 dsa_area *
diff --git a/src/include/access/brin.h b/src/include/access/brin.h
index 896824a..3f4c29b 100644
--- a/src/include/access/brin.h
+++ b/src/include/access/brin.h
@@ -22,6 +22,7 @@ typedef struct BrinOptions
 {
 	int32		vl_len_;		/* varlena header (do not touch directly!) */
 	BlockNumber pagesPerRange;
+	bool		autosummarize;
 } BrinOptions;
 
 #define BRIN_DEFAULT_PAGES_PER_RANGE	128
@@ -29,5 +30,9 @@ typedef struct BrinOptions
 	((relation)->rd_options ? \
 	 ((BrinOptions *) (relation)->rd_options)->pagesPerRange : \
 	  BRIN_DEFAULT_PAGES_PER_RANGE)
+#define BrinGetAutoSummarize(relation) \
+	((relation)->rd_options ? \
+	 ((BrinOptions *) (relation)->rd_options)->autosummarize : \
+	  false)
 
 #endif   /* BRIN_H */
diff --git a/src/include/postmaster/autovacuum.h b/src/include/postmaster/autovacuum.h
index 99d7f09..a871508 100644
--- a/src/include/postmaster/autovacuum.h
+++ b/src/include/postmaster/autovacuum.h
@@ -14,6 +14,15 @@
 #ifndef AUTOVACUUM_H
 #define AUTOVACUUM_H
 
+/*
+ * Other processes can request specific work from autovacuum, identified by
+ * AutoVacuumWorkItem elements.
+ */
+typedef enum
+{
+	AVW_BRINSummarizeRange
+} AutoVacuumWorkItemType;
+
 
 /* GUC variables */
 extern bool autovacuum_start_daemon;
@@ -60,6 +69,9 @@ extern void AutovacuumWorkerIAm(void);
 extern void AutovacuumLauncherIAm(void);
 #endif
 
+extern void AutoVacuumRequestWork(AutoVacuumWorkItemType type,
+					  Oid relationId);
+
 /* shared memory stuff */
 extern Size AutoVacuumShmemSize(void);
 extern void AutoVacuumShmemInit(void);
diff --git a/src/include/storage/lwlock.h b/src/include/storage/lwlock.h
index 8bd93c3..df27aca 100644
--- a/src/include/storage/lwlock.h
+++ b/src/include/storage/lwlock.h
@@ -211,6 +211,7 @@ typedef enum BuiltinTrancheIds
 	LWTRANCHE_BUFFER_MAPPING,
 	LWTRANCHE_LOCK_MANAGER,
 	LWTRANCHE_PREDICATE_LOCK_MANAGER,
+	LWTRANCHE_AUTOVACUUM,
 	LWTRANCHE_PARALLEL_QUERY_DSA,
 	LWTRANCHE_FIRST_USER_DEFINED
 }	BuiltinTrancheIds;