Allow VACUUM to be run with index cleanup disabled.

This commit adds a new reloption, vacuum_index_cleanup, which
controls whether index cleanup is performed for a particular
relation by default.  It also adds a new option to the VACUUM
command, INDEX_CLEANUP, which can be used to override the
reloption.  If neither the reloption nor the VACUUM option is
used, the default is true, as before.

Masahiko Sawada, reviewed and tested by Nathan Bossart, Alvaro
Herrera, Kyotaro Horiguchi, Darafei Praliaskouski, and me.
The wording of the documentation is mostly due to me.

Discussion: http://postgr.es/m/CAD21AoAt5R3DNUZSjOoXDUY=naYPUOuffVsRzuTYMz29yLzQCA@mail.gmail.com

Author: robertmhaas

doc/src/sgml/ref/create_table.sgml

@@ -1389,6 +1389,21 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><literal>vacuum_index_cleanup</literal> (<type>boolean</type>)</term>
+    <listitem>
+     <para>
+      Enables or disables index cleanup when <command>VACUUM</command> is
+      run on this table.  The default value is <literal>true</literal>.
+      Disabling index cleanup can speed up <command>VACUUM</command> very
+      significantly, but may also lead to severely bloated indexes if table
+      modifications are frequent.  The <literal>INDEX_CLEANUP</literal>
+      parameter to <xref linkend="sql-vacuum"/>, if specified, overrides
+      the value of this option.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><literal>autovacuum_vacuum_threshold</literal>, <literal>toast.autovacuum_vacuum_threshold</literal> (<type>integer</type>)</term>
     <listitem>

doc/src/sgml/ref/vacuum.sgml

@@ -32,6 +32,7 @@ VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [ <replaceable class="paramet
     ANALYZE [ <replaceable class="parameter">boolean</replaceable> ]
     DISABLE_PAGE_SKIPPING [ <replaceable class="parameter">boolean</replaceable> ]
     SKIP_LOCKED [ <replaceable class="parameter">boolean</replaceable> ]
+    INDEX_CLEANUP [ <replaceable class="parameter">boolean</replaceable> ]
 
 <phrase>and <replaceable class="parameter">table_and_columns</replaceable> is:</phrase>
 
@@ -181,6 +182,28 @@ VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [ <replaceable class="paramet
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><literal>INDEX_CLEANUP</literal></term>
+    <listitem>
+     <para>
+      Specifies that <command>VACUUM</command> should attempt to remove
+      index entries pointing to dead tuples.  This is normally the desired
+      behavior and is the default unless the
+      <literal>vacuum_index_cleanup</literal> option has been set to false
+      for the table to be vacuumed.  Setting this option to false may be
+      useful when it is necessary to make vacuum run as quickly as possible,
+      for example to avoid imminent transaction ID wraparound
+      (see <xref linkend="vacuum-for-wraparound"/>).  However, if index
+      cleanup is not performed regularly, performance may suffer, because
+      as the table is modified, indexes will accumulate dead tuples
+      and the table itself will accumulate dead line pointers that cannot be
+      removed until index cleanup is completed.  This option has no effect
+      for tables that do not have an index and is ignored if the
+      <literal>FULL</literal> is used.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><replaceable class="parameter">boolean</replaceable></term>
     <listitem>

src/backend/access/common/reloptions.c

@@ -138,6 +138,15 @@ static relopt_bool boolRelOpts[] =
 		},
 		false
 	},
+	{
+		{
+			"vacuum_index_cleanup",
+			"Enables index vacuuming and index cleanup",
+			RELOPT_KIND_HEAP,
+			ShareUpdateExclusiveLock
+		},
+		true
+	},
 	/* list terminator */
 	{{NULL}}
 };
@@ -1388,7 +1397,9 @@ default_reloptions(Datum reloptions, bool validate, relopt_kind kind)
 		{"parallel_workers", RELOPT_TYPE_INT,
 		offsetof(StdRdOptions, parallel_workers)},
 		{"vacuum_cleanup_index_scale_factor", RELOPT_TYPE_REAL,
-		offsetof(StdRdOptions, vacuum_cleanup_index_scale_factor)}
+		offsetof(StdRdOptions, vacuum_cleanup_index_scale_factor)},
+		{"vacuum_index_cleanup", RELOPT_TYPE_BOOL,
+		offsetof(StdRdOptions, vacuum_index_cleanup)}
 	};
 
 	options = parseRelOptions(reloptions, validate, kind, &numoptions);

src/backend/access/heap/vacuumlazy.c

@@ -112,8 +112,8 @@
 
 typedef struct LVRelStats
 {
-	/* hasindex = true means two-pass strategy; false means one-pass */
-	bool		hasindex;
+	/* useindex = true means two-pass strategy; false means one-pass */
+	bool		useindex;
 	/* Overall statistics about rel */
 	BlockNumber old_rel_pages;	/* previous value of pg_class.relpages */
 	BlockNumber rel_pages;		/* total number of pages */
@@ -125,6 +125,8 @@ typedef struct LVRelStats
 	double		new_rel_tuples; /* new estimated total # of tuples */
 	double		new_live_tuples;	/* new estimated total # of live tuples */
 	double		new_dead_tuples;	/* new estimated total # of dead tuples */
+	double		nleft_dead_tuples;	/* # of dead tuples we left */
+	double		nleft_dead_itemids;	/* # of dead item pointers we left */
 	BlockNumber pages_removed;
 	double		tuples_deleted;
 	BlockNumber nonempty_pages; /* actually, last nonempty page + 1 */
@@ -150,7 +152,7 @@ static BufferAccessStrategy vac_strategy;
 
 
 /* non-export function prototypes */
-static void lazy_scan_heap(Relation onerel, int options,
+static void lazy_scan_heap(Relation onerel, VacuumParams *params,
 			   LVRelStats *vacrelstats, Relation *Irel, int nindexes,
 			   bool aggressive);
 static void lazy_vacuum_heap(Relation onerel, LVRelStats *vacrelstats, BlockNumber nblocks);
@@ -209,6 +211,7 @@ heap_vacuum_rel(Relation onerel, VacuumParams *params,
 	MultiXactId new_min_multi;
 
 	Assert(params != NULL);
+	Assert(params->index_cleanup != VACOPT_TERNARY_DEFAULT);
 
 	/* measure elapsed time iff autovacuum logging requires it */
 	if (IsAutoVacuumWorkerProcess() && params->log_min_duration >= 0)
@@ -275,10 +278,11 @@ heap_vacuum_rel(Relation onerel, VacuumParams *params,
 
 	/* Open all indexes of the relation */
 	vac_open_indexes(onerel, RowExclusiveLock, &nindexes, &Irel);
-	vacrelstats->hasindex = (nindexes > 0);
+	vacrelstats->useindex = (nindexes > 0 &&
+							 params->index_cleanup == VACOPT_TERNARY_ENABLED);
 
 	/* Do the vacuuming */
-	lazy_scan_heap(onerel, params->options, vacrelstats, Irel, nindexes, aggressive);
+	lazy_scan_heap(onerel, params, vacrelstats, Irel, nindexes, aggressive);
 
 	/* Done with indexes */
 	vac_close_indexes(nindexes, Irel, NoLock);
@@ -349,7 +353,7 @@ heap_vacuum_rel(Relation onerel, VacuumParams *params,
 						new_rel_pages,
 						new_live_tuples,
 						new_rel_allvisible,
-						vacrelstats->hasindex,
+						nindexes > 0,
 						new_frozen_xid,
 						new_min_multi,
 						false);
@@ -419,6 +423,12 @@ heap_vacuum_rel(Relation onerel, VacuumParams *params,
 							 vacrelstats->new_rel_tuples,
 							 vacrelstats->new_dead_tuples,
 							 OldestXmin);
+			if (vacrelstats->nleft_dead_tuples > 0 ||
+				vacrelstats->nleft_dead_itemids > 0)
+				appendStringInfo(&buf,
+								 _("%.0f tuples and %.0f item identifiers are left as dead.\n"),
+								 vacrelstats->nleft_dead_tuples,
+								 vacrelstats->nleft_dead_itemids);
 			appendStringInfo(&buf,
 							 _("buffer usage: %d hits, %d misses, %d dirtied\n"),
 							 VacuumPageHit,
@@ -485,7 +495,7 @@ vacuum_log_cleanup_info(Relation rel, LVRelStats *vacrelstats)
  *		reference them have been killed.
  */
 static void
-lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
+lazy_scan_heap(Relation onerel, VacuumParams *params, LVRelStats *vacrelstats,
 			   Relation *Irel, int nindexes, bool aggressive)
 {
 	BlockNumber nblocks,
@@ -501,7 +511,10 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
 				live_tuples,	/* live tuples (reltuples estimate) */
 				tups_vacuumed,	/* tuples cleaned up by vacuum */
 				nkeep,			/* dead-but-not-removable tuples */
-				nunused;		/* unused item pointers */
+				nunused,		/* unused item pointers */
+				nleft_dead_tuples,		/* tuples we left as dead */
+				nleft_dead_itemids;		/* item pointers we left as dead,
+										 * includes nleft_dead_tuples. */
 	IndexBulkDeleteResult **indstats;
 	int			i;
 	PGRUsage	ru0;
@@ -534,6 +547,7 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
 	empty_pages = vacuumed_pages = 0;
 	next_fsm_block_to_vacuum = (BlockNumber) 0;
 	num_tuples = live_tuples = tups_vacuumed = nkeep = nunused = 0;
+	nleft_dead_itemids = nleft_dead_tuples = 0;
 
 	indstats = (IndexBulkDeleteResult **)
 		palloc0(nindexes * sizeof(IndexBulkDeleteResult *));
@@ -599,7 +613,7 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
 	 * be replayed on any hot standby, where it can be disruptive.
 	 */
 	next_unskippable_block = 0;
-	if ((options & VACOPT_DISABLE_PAGE_SKIPPING) == 0)
+	if ((params->options & VACOPT_DISABLE_PAGE_SKIPPING) == 0)
 	{
 		while (next_unskippable_block < nblocks)
 		{
@@ -654,7 +668,7 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
 		{
 			/* Time to advance next_unskippable_block */
 			next_unskippable_block++;
-			if ((options & VACOPT_DISABLE_PAGE_SKIPPING) == 0)
+			if ((params->options & VACOPT_DISABLE_PAGE_SKIPPING) == 0)
 			{
 				while (next_unskippable_block < nblocks)
 				{
@@ -1070,7 +1084,17 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
 						HeapTupleIsHeapOnly(&tuple))
 						nkeep += 1;
 					else
+					{
 						tupgone = true; /* we can delete the tuple */
+
+						/*
+						 * Since this dead tuple will not be vacuumed and
+						 * ignored when index cleanup is disabled we count
+						 * count it for reporting.
+						 */
+						if (params->index_cleanup == VACOPT_TERNARY_ENABLED)
+							nleft_dead_tuples++;
+					}
 					all_visible = false;
 					break;
 				case HEAPTUPLE_LIVE:
@@ -1222,23 +1246,40 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
 		}
 
 		/*
-		 * If there are no indexes then we can vacuum the page right now
-		 * instead of doing a second scan.
+		 * If there are no indexes we can vacuum the page right now instead of
+		 * doing a second scan. Also we don't do that but forget dead tuples
+		 * when index cleanup is disabled.
 		 */
-		if (nindexes == 0 &&
-			vacrelstats->num_dead_tuples > 0)
+		if (!vacrelstats->useindex && vacrelstats->num_dead_tuples > 0)
 		{
-			/* Remove tuples from heap */
-			lazy_vacuum_page(onerel, blkno, buf, 0, vacrelstats, &vmbuffer);
-			has_dead_tuples = false;
+			if (nindexes == 0)
+			{
+				/* Remove tuples from heap if the table has no index */
+				lazy_vacuum_page(onerel, blkno, buf, 0, vacrelstats, &vmbuffer);
+				vacuumed_pages++;
+				has_dead_tuples = false;
+			}
+			else
+			{
+				/*
+				 * Here, we have indexes but index cleanup is disabled. Instead of
+				 * vacuuming the dead tuples on the heap, we just forget them.
+				 *
+				 * Note that vacrelstats->dead_tuples could have tuples which
+				 * became dead after HOT-pruning but are not marked dead yet.
+				 * We do not process them because it's a very rare condition, and
+				 * the next vacuum will process them anyway.
+				 */
+				Assert(params->index_cleanup == VACOPT_TERNARY_DISABLED);
+				nleft_dead_itemids += vacrelstats->num_dead_tuples;
+			}
 
 			/*
 			 * Forget the now-vacuumed tuples, and press on, but be careful
 			 * not to reset latestRemovedXid since we want that value to be
 			 * valid.
 			 */
 			vacrelstats->num_dead_tuples = 0;
-			vacuumed_pages++;
 
 			/*
 			 * Periodically do incremental FSM vacuuming to make newly-freed
@@ -1357,14 +1398,21 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
 			RecordPageWithFreeSpace(onerel, blkno, freespace, nblocks);
 	}
 
+	/* No dead tuples should be left if index cleanup is enabled */
+	Assert((params->index_cleanup == VACOPT_TERNARY_ENABLED &&
+			nleft_dead_tuples == 0 && nleft_dead_itemids == 0) ||
+		   params->index_cleanup == VACOPT_TERNARY_DISABLED);
+
 	/* report that everything is scanned and vacuumed */
 	pgstat_progress_update_param(PROGRESS_VACUUM_HEAP_BLKS_SCANNED, blkno);
 
 	pfree(frozen);
 
 	/* save stats for use later */
 	vacrelstats->tuples_deleted = tups_vacuumed;
-	vacrelstats->new_dead_tuples = nkeep;
+	vacrelstats->new_dead_tuples = nkeep + nleft_dead_tuples;
+	vacrelstats->nleft_dead_tuples = nleft_dead_tuples;
+	vacrelstats->nleft_dead_itemids = nleft_dead_itemids;
 
 	/* now we can compute the new value for pg_class.reltuples */
 	vacrelstats->new_live_tuples = vac_estimate_reltuples(onerel,
@@ -1433,8 +1481,11 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
 								 PROGRESS_VACUUM_PHASE_INDEX_CLEANUP);
 
 	/* Do post-vacuum cleanup and statistics update for each index */
-	for (i = 0; i < nindexes; i++)
-		lazy_cleanup_index(Irel[i], indstats[i], vacrelstats);
+	if (vacrelstats->useindex)
+	{
+		for (i = 0; i < nindexes; i++)
+			lazy_cleanup_index(Irel[i], indstats[i], vacrelstats);
+	}
 
 	/* If no indexes, make log report that lazy_vacuum_heap would've made */
 	if (vacuumed_pages)
@@ -1465,6 +1516,8 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
 									"%u pages are entirely empty.\n",
 									empty_pages),
 					 empty_pages);
+	appendStringInfo(&buf, "%.0f tuples and %.0f item identifiers are left as dead.\n",
+					 nleft_dead_tuples, nleft_dead_itemids);
 	appendStringInfo(&buf, _("%s."), pg_rusage_show(&ru0));
 
 	ereport(elevel,
@@ -2110,7 +2163,7 @@ lazy_space_alloc(LVRelStats *vacrelstats, BlockNumber relblocks)
 	autovacuum_work_mem != -1 ?
 	autovacuum_work_mem : maintenance_work_mem;
 
-	if (vacrelstats->hasindex)
+	if (vacrelstats->useindex)
 	{
 		maxtuples = (vac_work_mem * 1024L) / sizeof(ItemPointerData);
 		maxtuples = Min(maxtuples, INT_MAX);

src/backend/commands/vacuum.c

@@ -76,6 +76,7 @@ static void vac_truncate_clog(TransactionId frozenXID,
 				  TransactionId lastSaneFrozenXid,
 				  MultiXactId lastSaneMinMulti);
 static bool vacuum_rel(Oid relid, RangeVar *relation, VacuumParams *params);
+static VacOptTernaryValue get_vacopt_ternary_value(DefElem *def);
 
 /*
  * Primary entry point for manual VACUUM and ANALYZE commands
@@ -95,6 +96,9 @@ ExecVacuum(ParseState *pstate, VacuumStmt *vacstmt, bool isTopLevel)
 	bool disable_page_skipping = false;
 	ListCell	*lc;
 
+	/* Set default value */
+	params.index_cleanup = VACOPT_TERNARY_DEFAULT;
+
 	/* Parse options list */
 	foreach(lc, vacstmt->options)
 	{
@@ -120,6 +124,8 @@ ExecVacuum(ParseState *pstate, VacuumStmt *vacstmt, bool isTopLevel)
 			full = defGetBoolean(opt);
 		else if (strcmp(opt->defname, "disable_page_skipping") == 0)
 			disable_page_skipping = defGetBoolean(opt);
+		else if (strcmp(opt->defname, "index_cleanup") == 0)
+			params.index_cleanup = get_vacopt_ternary_value(opt);
 		else
 			ereport(ERROR,
 					(errcode(ERRCODE_SYNTAX_ERROR),
@@ -1719,6 +1725,16 @@ vacuum_rel(Oid relid, RangeVar *relation, VacuumParams *params)
 	onerelid = onerel->rd_lockInfo.lockRelId;
 	LockRelationIdForSession(&onerelid, lmode);
 
+	/* Set index cleanup option based on reloptions if not yet */
+	if (params->index_cleanup == VACOPT_TERNARY_DEFAULT)
+	{
+		if (onerel->rd_options == NULL ||
+			((StdRdOptions *) onerel->rd_options)->vacuum_index_cleanup)
+			params->index_cleanup = VACOPT_TERNARY_ENABLED;
+		else
+			params->index_cleanup = VACOPT_TERNARY_DISABLED;
+	}
+
 	/*
 	 * Remember the relation's TOAST relation for later, if the caller asked
 	 * us to process it.  In VACUUM FULL, though, the toast table is
@@ -1899,3 +1915,15 @@ vacuum_delay_point(void)
 		CHECK_FOR_INTERRUPTS();
 	}
 }
+
+/*
+ * A wrapper function of defGetBoolean().
+ *
+ * This function returns VACOPT_TERNARY_ENABLED and VACOPT_TERNARY_DISABLED
+ * instead of true and false.
+ */
+static VacOptTernaryValue
+get_vacopt_ternary_value(DefElem *def)
+{
+	return defGetBoolean(def) ? VACOPT_TERNARY_ENABLED : VACOPT_TERNARY_DISABLED;
+}

src/backend/postmaster/autovacuum.c

@@ -2886,6 +2886,7 @@ table_recheck_autovac(Oid relid, HTAB *table_toast_map,
 			(dovacuum ? VACOPT_VACUUM : 0) |
 			(doanalyze ? VACOPT_ANALYZE : 0) |
 			(!wraparound ? VACOPT_SKIP_LOCKED : 0);
+		tab->at_params.index_cleanup = VACOPT_TERNARY_DEFAULT;
 		tab->at_params.freeze_min_age = freeze_min_age;
 		tab->at_params.freeze_table_age = freeze_table_age;
 		tab->at_params.multixact_freeze_min_age = multixact_freeze_min_age;