Add TRUNCATE parameter to VACUUM.

This commit adds new parameter to VACUUM command, TRUNCATE,
which specifies that VACUUM should attempt to truncate off
any empty pages at the end of the table and allow the disk space
for the truncated pages to be returned to the operating system.

This parameter, if specified, overrides the vacuum_truncate
reloption. If neither the reloption nor the VACUUM option is
used, the default is true, as before.

Author: Fujii Masao
Reviewed-by: Julien Rouhaud, Masahiko Sawada
Discussion: https://postgr.es/m/CAD21AoD+qtrSDL=GSma4Wd3kLYLeRC0hPna-YAdkDeV4z156vg@mail.gmail.com

9 files changed, 81 insertions, 10 deletions

diff --git a/doc/src/sgml/ref/create_table.sgml b/doc/src/sgml/ref/create_table.sgml
index 786510f94ca..19af4eed9c3 100644
--- a/doc/src/sgml/ref/create_table.sgml
+++ b/doc/src/sgml/ref/create_table.sgml
@@ -1418,7 +1418,7 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
       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
+      parameter of <xref linkend="sql-vacuum"/>, if specified, overrides
       the value of this option.
      </para>
     </listitem>
@@ -1438,7 +1438,9 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
       autovacuum do the truncation and the disk space for
       the truncated pages is returned to the operating system.
       Note that the truncation requires <literal>ACCESS EXCLUSIVE</literal>
-      lock on the table.
+      lock on the table. The <literal>TRUNCATE</literal> parameter
+      of <xref linkend="sql-vacuum"/>, if specified, overrides the value
+      of this option.
      </para>
     </listitem>
    </varlistentry>
diff --git a/doc/src/sgml/ref/vacuum.sgml b/doc/src/sgml/ref/vacuum.sgml
index c652f8b0bcd..f9b0fb87945 100644
--- a/doc/src/sgml/ref/vacuum.sgml
+++ b/doc/src/sgml/ref/vacuum.sgml
@@ -33,6 +33,7 @@ VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [ <replaceable class="paramet
     DISABLE_PAGE_SKIPPING [ <replaceable class="parameter">boolean</replaceable> ]
     SKIP_LOCKED [ <replaceable class="parameter">boolean</replaceable> ]
     INDEX_CLEANUP [ <replaceable class="parameter">boolean</replaceable> ]
+    TRUNCATE [ <replaceable class="parameter">boolean</replaceable> ]
 
 <phrase>and <replaceable class="parameter">table_and_columns</replaceable> is:</phrase>
 
@@ -205,6 +206,24 @@ VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [ <replaceable class="paramet
    </varlistentry>
 
    <varlistentry>
+    <term><literal>TRUNCATE</literal></term>
+    <listitem>
+     <para>
+      Specifies that <command>VACUUM</command> should attempt to
+      truncate off any empty pages at the end of the table and allow
+      the disk space for the truncated pages to be returned to
+      the operating system. This is normally the desired behavior
+      and is the default unless the <literal>vacuum_truncate</literal>
+      option has been set to false for the table to be vacuumed.
+      Setting this option to false may be useful to avoid
+      <literal>ACCESS EXCLUSIVE</literal> lock on the table that
+      the truncation requires. This option is ignored if the
+      <literal>FULL</literal> option is used.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
     <term><replaceable class="parameter">boolean</replaceable></term>
     <listitem>
      <para>
diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c
index 0f70dc883d1..f1a79059cdb 100644
--- a/src/backend/access/heap/vacuumlazy.c
+++ b/src/backend/access/heap/vacuumlazy.c
@@ -163,7 +163,8 @@ static void lazy_cleanup_index(Relation indrel,
 				   LVRelStats *vacrelstats);
 static int lazy_vacuum_page(Relation onerel, BlockNumber blkno, Buffer buffer,
 				 int tupindex, LVRelStats *vacrelstats, Buffer *vmbuffer);
-static bool should_attempt_truncation(Relation rel, LVRelStats *vacrelstats);
+static bool should_attempt_truncation(VacuumParams *params,
+						 LVRelStats *vacrelstats);
 static void lazy_truncate_heap(Relation onerel, LVRelStats *vacrelstats);
 static BlockNumber count_nondeletable_pages(Relation onerel,
 						 LVRelStats *vacrelstats);
@@ -210,6 +211,7 @@ heap_vacuum_rel(Relation onerel, VacuumParams *params,
 
 	Assert(params != NULL);
 	Assert(params->index_cleanup != VACOPT_TERNARY_DEFAULT);
+	Assert(params->truncate != VACOPT_TERNARY_DEFAULT);
 
 	/* not every AM requires these to be valid, but heap does */
 	Assert(TransactionIdIsNormal(onerel->rd_rel->relfrozenxid));
@@ -308,7 +310,7 @@ heap_vacuum_rel(Relation onerel, VacuumParams *params,
 	/*
 	 * Optionally truncate the relation.
 	 */
-	if (should_attempt_truncation(onerel, vacrelstats))
+	if (should_attempt_truncation(params, vacrelstats))
 		lazy_truncate_heap(onerel, vacrelstats);
 
 	/* Report that we are now doing final cleanup */
@@ -652,7 +654,7 @@ lazy_scan_heap(Relation onerel, VacuumParams *params, LVRelStats *vacrelstats,
 
 		/* see note above about forcing scanning of last page */
 #define FORCE_CHECK_PAGE() \
-		(blkno == nblocks - 1 && should_attempt_truncation(onerel, vacrelstats))
+		(blkno == nblocks - 1 && should_attempt_truncation(params, vacrelstats))
 
 		pgstat_progress_update_param(PROGRESS_VACUUM_HEAP_BLKS_SCANNED, blkno);
 
@@ -1845,12 +1847,11 @@ lazy_cleanup_index(Relation indrel,
  * careful to depend only on fields that lazy_scan_heap updates on-the-fly.
  */
 static bool
-should_attempt_truncation(Relation rel, LVRelStats *vacrelstats)
+should_attempt_truncation(VacuumParams *params, LVRelStats *vacrelstats)
 {
 	BlockNumber possibly_freeable;
 
-	if (rel->rd_options != NULL &&
-		((StdRdOptions *) rel->rd_options)->vacuum_truncate == false)
+	if (params->truncate == VACOPT_TERNARY_DISABLED)
 		return false;
 
 	possibly_freeable = vacrelstats->rel_pages - vacrelstats->nonempty_pages;
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index 94fb6f26063..afdd3307acd 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -98,6 +98,7 @@ ExecVacuum(ParseState *pstate, VacuumStmt *vacstmt, bool isTopLevel)
 
 	/* Set default value */
 	params.index_cleanup = VACOPT_TERNARY_DEFAULT;
+	params.truncate = VACOPT_TERNARY_DEFAULT;
 
 	/* Parse options list */
 	foreach(lc, vacstmt->options)
@@ -126,6 +127,8 @@ ExecVacuum(ParseState *pstate, VacuumStmt *vacstmt, bool isTopLevel)
 			disable_page_skipping = defGetBoolean(opt);
 		else if (strcmp(opt->defname, "index_cleanup") == 0)
 			params.index_cleanup = get_vacopt_ternary_value(opt);
+		else if (strcmp(opt->defname, "truncate") == 0)
+			params.truncate = get_vacopt_ternary_value(opt);
 		else
 			ereport(ERROR,
 					(errcode(ERRCODE_SYNTAX_ERROR),
@@ -1760,6 +1763,16 @@ vacuum_rel(Oid relid, RangeVar *relation, VacuumParams *params)
 			params->index_cleanup = VACOPT_TERNARY_DISABLED;
 	}
 
+	/* Set truncate option based on reloptions if not yet */
+	if (params->truncate == VACOPT_TERNARY_DEFAULT)
+	{
+		if (onerel->rd_options == NULL ||
+			((StdRdOptions *) onerel->rd_options)->vacuum_truncate)
+			params->truncate = VACOPT_TERNARY_ENABLED;
+		else
+			params->truncate = 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
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 53c91d92778..acd8a9280b9 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -2887,6 +2887,7 @@ table_recheck_autovac(Oid relid, HTAB *table_toast_map,
 			(doanalyze ? VACOPT_ANALYZE : 0) |
 			(!wraparound ? VACOPT_SKIP_LOCKED : 0);
 		tab->at_params.index_cleanup = VACOPT_TERNARY_DEFAULT;
+		tab->at_params.truncate = 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;
diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index bcddc7601e4..e4c03de221f 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -3466,8 +3466,8 @@ psql_completion(const char *text, int start, int end)
 		if (ends_with(prev_wd, '(') || ends_with(prev_wd, ','))
 			COMPLETE_WITH("FULL", "FREEZE", "ANALYZE", "VERBOSE",
 						  "DISABLE_PAGE_SKIPPING", "SKIP_LOCKED",
-						  "INDEX_CLEANUP");
-		else if (TailMatches("FULL|FREEZE|ANALYZE|VERBOSE|DISABLE_PAGE_SKIPPING|SKIP_LOCKED|INDEX_CLEANUP"))
+						  "INDEX_CLEANUP", "TRUNCATE");
+		else if (TailMatches("FULL|FREEZE|ANALYZE|VERBOSE|DISABLE_PAGE_SKIPPING|SKIP_LOCKED|INDEX_CLEANUP|TRUNCATE"))
 			COMPLETE_WITH("ON", "OFF");
 	}
 	else if (HeadMatches("VACUUM") && TailMatches("("))
diff --git a/src/include/commands/vacuum.h b/src/include/commands/vacuum.h
index 9cc6e0d0235..270f61b0832 100644
--- a/src/include/commands/vacuum.h
+++ b/src/include/commands/vacuum.h
@@ -182,6 +182,8 @@ typedef struct VacuumParams
 									 * to use default */
 	VacOptTernaryValue index_cleanup;	/* Do index vacuum and cleanup,
 										* default value depends on reloptions */
+	VacOptTernaryValue truncate;	/* Truncate empty pages at the end,
+										* default value depends on reloptions */
 } VacuumParams;
 
 /* GUC parameters */
diff --git a/src/test/regress/expected/vacuum.out b/src/test/regress/expected/vacuum.out
index 6ba7cd726bc..e6657a675e1 100644
--- a/src/test/regress/expected/vacuum.out
+++ b/src/test/regress/expected/vacuum.out
@@ -88,6 +88,28 @@ VACUUM (INDEX_CLEANUP FALSE, FREEZE TRUE) vaccluster;
 -- index cleanup option is ignored if VACUUM FULL
 VACUUM (INDEX_CLEANUP TRUE, FULL TRUE) no_index_cleanup;
 VACUUM (FULL TRUE) no_index_cleanup;
+-- TRUNCATE option
+CREATE TABLE vac_truncate_test(i INT NOT NULL, j text)
+	WITH (vacuum_truncate=true, autovacuum_enabled=false);
+INSERT INTO vac_truncate_test VALUES (1, NULL), (NULL, NULL);
+ERROR:  null value in column "i" violates not-null constraint
+DETAIL:  Failing row contains (null, null).
+VACUUM (TRUNCATE FALSE) vac_truncate_test;
+SELECT pg_relation_size('vac_truncate_test') > 0;
+ ?column? 
+----------
+ t
+(1 row)
+
+VACUUM vac_truncate_test;
+SELECT pg_relation_size('vac_truncate_test') = 0;
+ ?column? 
+----------
+ t
+(1 row)
+
+VACUUM (TRUNCATE FALSE, FULL TRUE) vac_truncate_test;
+DROP TABLE vac_truncate_test;
 -- partitioned table
 CREATE TABLE vacparted (a int, b char) PARTITION BY LIST (a);
 CREATE TABLE vacparted1 PARTITION OF vacparted FOR VALUES IN (1);
diff --git a/src/test/regress/sql/vacuum.sql b/src/test/regress/sql/vacuum.sql
index 57e0f354dda..4fa90940dc8 100644
--- a/src/test/regress/sql/vacuum.sql
+++ b/src/test/regress/sql/vacuum.sql
@@ -71,6 +71,17 @@ VACUUM (INDEX_CLEANUP FALSE, FREEZE TRUE) vaccluster;
 VACUUM (INDEX_CLEANUP TRUE, FULL TRUE) no_index_cleanup;
 VACUUM (FULL TRUE) no_index_cleanup;
 
+-- TRUNCATE option
+CREATE TABLE vac_truncate_test(i INT NOT NULL, j text)
+	WITH (vacuum_truncate=true, autovacuum_enabled=false);
+INSERT INTO vac_truncate_test VALUES (1, NULL), (NULL, NULL);
+VACUUM (TRUNCATE FALSE) vac_truncate_test;
+SELECT pg_relation_size('vac_truncate_test') > 0;
+VACUUM vac_truncate_test;
+SELECT pg_relation_size('vac_truncate_test') = 0;
+VACUUM (TRUNCATE FALSE, FULL TRUE) vac_truncate_test;
+DROP TABLE vac_truncate_test;
+
 -- partitioned table
 CREATE TABLE vacparted (a int, b char) PARTITION BY LIST (a);
 CREATE TABLE vacparted1 PARTITION OF vacparted FOR VALUES IN (1);