Add option SKIP_LOCKED to VACUUM and ANALYZE

When specified, this option allows VACUUM to skip the work on a relation
if there is a conflicting lock on it when trying to open it at the
beginning of its processing.

Similarly to autovacuum, this comes with a couple of limitations while
the relation is processed which can cause the process to still block:
- when opening the relation indexes.
- when acquiring row samples for table inheritance trees, partition trees
or certain types of foreign tables, and that a lock is taken on some
leaves of such trees.

Author: Nathan Bossart
Reviewed-by: Michael Paquier, Andres Freund, Masahiko Sawada
Discussion: https://postgr.es/m/9EF7EBE4-720D-4CF1-9D0E-4403D7E92990@amazon.com
Discussion: https://postgr.es/m/20171201160907.27110.74730@wrigleys.postgresql.org

doc/src/sgml/ref/analyze.sgml

@@ -27,6 +27,7 @@ ANALYZE [ VERBOSE ] [ <replaceable class="parameter">table_and_columns</replacea
 <phrase>where <replaceable class="parameter">option</replaceable> can be one of:</phrase>
 
     VERBOSE
+    SKIP_LOCKED
 
 <phrase>and <replaceable class="parameter">table_and_columns</replaceable> is:</phrase>
 
@@ -76,6 +77,24 @@ ANALYZE [ VERBOSE ] [ <replaceable class="parameter">table_and_columns</replacea
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><literal>SKIP_LOCKED</literal></term>
+    <listitem>
+     <para>
+      Specifies that <command>ANALYZE</command> should not wait for any
+      conflicting locks to be released when beginning work on a relation:
+      if a relation cannot be locked immediately without waiting, the relation
+      is skipped.  Note that even with this option, <command>ANALYZE</command>
+      may still block when opening the relation's indexes or when acquiring
+      sample rows from partitions, table inheritance children, and some
+      types of foreign tables.  Also, while <command>ANALYZE</command>
+      ordinarily processes all partitions of specified partitioned tables,
+      this option will cause <command>ANALYZE</command> to skip all
+      partitions if there is a conflicting lock on the partitioned table.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><replaceable class="parameter">table_name</replaceable></term>
     <listitem>

doc/src/sgml/ref/vacuum.sgml

@@ -31,6 +31,7 @@ VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [ <replaceable class="paramet
     VERBOSE
     ANALYZE
     DISABLE_PAGE_SKIPPING
+    SKIP_LOCKED
 
 <phrase>and <replaceable class="parameter">table_and_columns</replaceable> is:</phrase>
 
@@ -160,6 +161,26 @@ VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [ <replaceable class="paramet
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><literal>SKIP_LOCKED</literal></term>
+    <listitem>
+     <para>
+      Specifies that <command>VACUUM</command> should not wait for any
+      conflicting locks to be released when beginning work on a relation:
+      if a relation cannot be locked immediately without waiting, the relation
+      is skipped.  Note that even with this option,
+      <command>VACUUM</command> may still block when opening the relation's
+      indexes.  Additionally, <command>VACUUM ANALYZE</command> may still
+      block when acquiring sample rows from partitions, table inheritance
+      children, and some types of foreign tables.  Also, while
+      <command>VACUUM</command> ordinarily processes all partitions of
+      specified partitioned tables, this option will cause
+      <command>VACUUM</command> to skip all partitions if there is a
+      conflicting lock on the partitioned table.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><replaceable class="parameter">table_name</replaceable></term>
     <listitem>

src/backend/commands/vacuum.c

@@ -622,6 +622,7 @@ expand_vacuum_rel(VacuumRelation *vrel, int options)
 		HeapTuple	tuple;
 		Form_pg_class classForm;
 		bool		include_parts;
+		int			rvr_opts;
 
 		/*
 		 * Since autovacuum workers supply OIDs when calling vacuum(), no
@@ -634,7 +635,30 @@ expand_vacuum_rel(VacuumRelation *vrel, int options)
 		 * below, as well as find_all_inheritors's expectation that the caller
 		 * holds some lock on the starting relation.
 		 */
-		relid = RangeVarGetRelid(vrel->relation, AccessShareLock, false);
+		rvr_opts = (options & VACOPT_SKIP_LOCKED) ? RVR_SKIP_LOCKED : 0;
+		relid = RangeVarGetRelidExtended(vrel->relation,
+										 AccessShareLock,
+										 rvr_opts,
+										 NULL, NULL);
+
+		/*
+		 * If the lock is unavailable, emit the same log statement that
+		 * vacuum_rel() and analyze_rel() would.
+		 */
+		if (!OidIsValid(relid))
+		{
+			if (options & VACOPT_VACUUM)
+				ereport(WARNING,
+						(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
+						 errmsg("skipping vacuum of \"%s\" --- lock not available",
+								vrel->relation->relname)));
+			else
+				ereport(WARNING,
+						(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
+						 errmsg("skipping analyze of \"%s\" --- lock not available",
+								vrel->relation->relname)));
+			return vacrels;
+		}
 
 		/*
 		 * To check whether the relation is a partitioned table and its

src/backend/parser/gram.y

@@ -10538,6 +10538,8 @@ vacuum_option_elem:
 				{
 					if (strcmp($1, "disable_page_skipping") == 0)
 						$$ = VACOPT_DISABLE_PAGE_SKIPPING;
+					else if (strcmp($1, "skip_locked") == 0)
+						$$ = VACOPT_SKIP_LOCKED;
 					else
 						ereport(ERROR,
 								(errcode(ERRCODE_SYNTAX_ERROR),
@@ -10571,6 +10573,16 @@ analyze_option_list:
 
 analyze_option_elem:
 			VERBOSE				{ $$ = VACOPT_VERBOSE; }
+			| IDENT
+				{
+					if (strcmp($1, "skip_locked") == 0)
+						$$ = VACOPT_SKIP_LOCKED;
+					else
+						ereport(ERROR,
+								(errcode(ERRCODE_SYNTAX_ERROR),
+								 errmsg("unrecognized ANALYZE option \"%s\"", $1),
+									 parser_errposition(@1)));
+				}
 		;
 
 analyze_keyword:

src/include/nodes/parsenodes.h

@@ -3154,8 +3154,7 @@ typedef enum VacuumOption
 	VACOPT_VERBOSE = 1 << 2,	/* print progress info */
 	VACOPT_FREEZE = 1 << 3,		/* FREEZE option */
 	VACOPT_FULL = 1 << 4,		/* FULL (non-concurrent) vacuum */
-	VACOPT_SKIP_LOCKED = 1 << 5,	/* skip if cannot get lock (autovacuum
+	VACOPT_SKIP_LOCKED = 1 << 5,	/* skip if cannot get lock */
-									 * only) */
 	VACOPT_SKIPTOAST = 1 << 6,	/* don't process the TOAST table, if any */
 	VACOPT_DISABLE_PAGE_SKIPPING = 1 << 7	/* don't skip any pages */
 } VacuumOption;

src/test/isolation/expected/vacuum-skip-locked.out

@@ -0,0 +1,171 @@
+Parsed test spec with 2 sessions
+
+starting permutation: lock_share vac_specified commit
+step lock_share: 
+	BEGIN;
+	LOCK part1 IN SHARE MODE;
+
+WARNING:  skipping vacuum of "part1" --- lock not available
+step vac_specified: VACUUM (SKIP_LOCKED) part1, part2;
+step commit: 
+	COMMIT;
+
+
+starting permutation: lock_share vac_all_parts commit
+step lock_share: 
+	BEGIN;
+	LOCK part1 IN SHARE MODE;
+
+step vac_all_parts: VACUUM (SKIP_LOCKED) parted;
+step commit: 
+	COMMIT;
+
+
+starting permutation: lock_share analyze_specified commit
+step lock_share: 
+	BEGIN;
+	LOCK part1 IN SHARE MODE;
+
+WARNING:  skipping analyze of "part1" --- lock not available
+step analyze_specified: ANALYZE (SKIP_LOCKED) part1, part2;
+step commit: 
+	COMMIT;
+
+
+starting permutation: lock_share analyze_all_parts commit
+step lock_share: 
+	BEGIN;
+	LOCK part1 IN SHARE MODE;
+
+step analyze_all_parts: ANALYZE (SKIP_LOCKED) parted;
+step commit: 
+	COMMIT;
+
+
+starting permutation: lock_share vac_analyze_specified commit
+step lock_share: 
+	BEGIN;
+	LOCK part1 IN SHARE MODE;
+
+WARNING:  skipping vacuum of "part1" --- lock not available
+step vac_analyze_specified: VACUUM (ANALYZE, SKIP_LOCKED) part1, part2;
+step commit: 
+	COMMIT;
+
+
+starting permutation: lock_share vac_analyze_all_parts commit
+step lock_share: 
+	BEGIN;
+	LOCK part1 IN SHARE MODE;
+
+step vac_analyze_all_parts: VACUUM (ANALYZE, SKIP_LOCKED) parted;
+step commit: 
+	COMMIT;
+
+
+starting permutation: lock_share vac_full_specified commit
+step lock_share: 
+	BEGIN;
+	LOCK part1 IN SHARE MODE;
+
+WARNING:  skipping vacuum of "part1" --- lock not available
+step vac_full_specified: VACUUM (SKIP_LOCKED, FULL) part1, part2;
+step commit: 
+	COMMIT;
+
+
+starting permutation: lock_share vac_full_all_parts commit
+step lock_share: 
+	BEGIN;
+	LOCK part1 IN SHARE MODE;
+
+step vac_full_all_parts: VACUUM (SKIP_LOCKED, FULL) parted;
+step commit: 
+	COMMIT;
+
+
+starting permutation: lock_access_exclusive vac_specified commit
+step lock_access_exclusive: 
+	BEGIN;
+	LOCK part1 IN ACCESS EXCLUSIVE MODE;
+
+WARNING:  skipping vacuum of "part1" --- lock not available
+step vac_specified: VACUUM (SKIP_LOCKED) part1, part2;
+step commit: 
+	COMMIT;
+
+
+starting permutation: lock_access_exclusive vac_all_parts commit
+step lock_access_exclusive: 
+	BEGIN;
+	LOCK part1 IN ACCESS EXCLUSIVE MODE;
+
+step vac_all_parts: VACUUM (SKIP_LOCKED) parted;
+step commit: 
+	COMMIT;
+
+
+starting permutation: lock_access_exclusive analyze_specified commit
+step lock_access_exclusive: 
+	BEGIN;
+	LOCK part1 IN ACCESS EXCLUSIVE MODE;
+
+WARNING:  skipping analyze of "part1" --- lock not available
+step analyze_specified: ANALYZE (SKIP_LOCKED) part1, part2;
+step commit: 
+	COMMIT;
+
+
+starting permutation: lock_access_exclusive analyze_all_parts commit
+step lock_access_exclusive: 
+	BEGIN;
+	LOCK part1 IN ACCESS EXCLUSIVE MODE;
+
+step analyze_all_parts: ANALYZE (SKIP_LOCKED) parted; <waiting ...>
+step commit: 
+	COMMIT;
+
+step analyze_all_parts: <... completed>
+
+starting permutation: lock_access_exclusive vac_analyze_specified commit
+step lock_access_exclusive: 
+	BEGIN;
+	LOCK part1 IN ACCESS EXCLUSIVE MODE;
+
+WARNING:  skipping vacuum of "part1" --- lock not available
+step vac_analyze_specified: VACUUM (ANALYZE, SKIP_LOCKED) part1, part2;
+step commit: 
+	COMMIT;
+
+
+starting permutation: lock_access_exclusive vac_analyze_all_parts commit
+step lock_access_exclusive: 
+	BEGIN;
+	LOCK part1 IN ACCESS EXCLUSIVE MODE;
+
+step vac_analyze_all_parts: VACUUM (ANALYZE, SKIP_LOCKED) parted; <waiting ...>
+step commit: 
+	COMMIT;
+
+step vac_analyze_all_parts: <... completed>
+
+starting permutation: lock_access_exclusive vac_full_specified commit
+step lock_access_exclusive: 
+	BEGIN;
+	LOCK part1 IN ACCESS EXCLUSIVE MODE;
+
+WARNING:  skipping vacuum of "part1" --- lock not available
+step vac_full_specified: VACUUM (SKIP_LOCKED, FULL) part1, part2;
+step commit: 
+	COMMIT;
+
+
+starting permutation: lock_access_exclusive vac_full_all_parts commit
+step lock_access_exclusive: 
+	BEGIN;
+	LOCK part1 IN ACCESS EXCLUSIVE MODE;
+
+step vac_full_all_parts: VACUUM (SKIP_LOCKED, FULL) parted;
+step commit: 
+	COMMIT;
+

src/test/isolation/isolation_schedule

@@ -67,6 +67,7 @@ test: vacuum-reltuples
 test: timeouts
 test: vacuum-concurrent-drop
 test: vacuum-conflict
+test: vacuum-skip-locked
 test: predicate-hash
 test: predicate-gist
 test: predicate-gin

src/test/isolation/specs/vacuum-skip-locked.spec

@@ -0,0 +1,59 @@
+# Test for SKIP_LOCKED option of VACUUM and ANALYZE commands.
+#
+# This also verifies that log messages are not emitted for skipped relations
+# that were not specified in the VACUUM or ANALYZE command.
+
+setup
+{
+	CREATE TABLE parted (a INT) PARTITION BY LIST (a);
+	CREATE TABLE part1 PARTITION OF parted FOR VALUES IN (1);
+	CREATE TABLE part2 PARTITION OF parted FOR VALUES IN (2);
+}
+
+teardown
+{
+	DROP TABLE IF EXISTS parted;
+}
+
+session "s1"
+step "lock_share"
+{
+	BEGIN;
+	LOCK part1 IN SHARE MODE;
+}
+step "lock_access_exclusive"
+{
+	BEGIN;
+	LOCK part1 IN ACCESS EXCLUSIVE MODE;
+}
+step "commit"
+{
+	COMMIT;
+}
+
+session "s2"
+step "vac_specified"		{ VACUUM (SKIP_LOCKED) part1, part2; }
+step "vac_all_parts"		{ VACUUM (SKIP_LOCKED) parted; }
+step "analyze_specified"	{ ANALYZE (SKIP_LOCKED) part1, part2; }
+step "analyze_all_parts"	{ ANALYZE (SKIP_LOCKED) parted; }
+step "vac_analyze_specified"	{ VACUUM (ANALYZE, SKIP_LOCKED) part1, part2; }
+step "vac_analyze_all_parts"	{ VACUUM (ANALYZE, SKIP_LOCKED) parted; }
+step "vac_full_specified"	{ VACUUM (SKIP_LOCKED, FULL) part1, part2; }
+step "vac_full_all_parts"	{ VACUUM (SKIP_LOCKED, FULL) parted; }
+
+permutation "lock_share" "vac_specified" "commit"
+permutation "lock_share" "vac_all_parts" "commit"
+permutation "lock_share" "analyze_specified" "commit"
+permutation "lock_share" "analyze_all_parts" "commit"
+permutation "lock_share" "vac_analyze_specified" "commit"
+permutation "lock_share" "vac_analyze_all_parts" "commit"
+permutation "lock_share" "vac_full_specified" "commit"
+permutation "lock_share" "vac_full_all_parts" "commit"
+permutation "lock_access_exclusive" "vac_specified" "commit"
+permutation "lock_access_exclusive" "vac_all_parts" "commit"
+permutation "lock_access_exclusive" "analyze_specified" "commit"
+permutation "lock_access_exclusive" "analyze_all_parts" "commit"
+permutation "lock_access_exclusive" "vac_analyze_specified" "commit"
+permutation "lock_access_exclusive" "vac_analyze_all_parts" "commit"
+permutation "lock_access_exclusive" "vac_full_specified" "commit"
+permutation "lock_access_exclusive" "vac_full_all_parts" "commit"

src/test/regress/expected/vacuum.out

@@ -115,10 +115,20 @@ ERROR:  column "does_not_exist" of relation "vacparted" does not exist
 -- parenthesized syntax for ANALYZE
 ANALYZE (VERBOSE) does_not_exist;
 ERROR:  relation "does_not_exist" does not exist
-ANALYZE (nonexistant-arg) does_not_exist;
+ANALYZE (nonexistent-arg) does_not_exist;
-ERROR:  syntax error at or near "nonexistant"
+ERROR:  unrecognized ANALYZE option "nonexistent"
-LINE 1: ANALYZE (nonexistant-arg) does_not_exist;
+LINE 1: ANALYZE (nonexistent-arg) does_not_exist;
                  ^
+-- ensure argument order independence, and that SKIP_LOCKED on non-existing
+-- relation still errors out.
+ANALYZE (SKIP_LOCKED, VERBOSE) does_not_exist;
+ERROR:  relation "does_not_exist" does not exist
+ANALYZE (VERBOSE, SKIP_LOCKED) does_not_exist;
+ERROR:  relation "does_not_exist" does not exist
+-- SKIP_LOCKED option
+VACUUM (SKIP_LOCKED) vactst;
+VACUUM (SKIP_LOCKED, FULL) vactst;
+ANALYZE (SKIP_LOCKED) vactst;
 DROP TABLE vaccluster;
 DROP TABLE vactst;
 DROP TABLE vacparted;

src/test/regress/sql/vacuum.sql

@@ -91,7 +91,17 @@ ANALYZE vactst (i), vacparted (does_not_exist);
 
 -- parenthesized syntax for ANALYZE
 ANALYZE (VERBOSE) does_not_exist;
-ANALYZE (nonexistant-arg) does_not_exist;
+ANALYZE (nonexistent-arg) does_not_exist;
+
+-- ensure argument order independence, and that SKIP_LOCKED on non-existing
+-- relation still errors out.
+ANALYZE (SKIP_LOCKED, VERBOSE) does_not_exist;
+ANALYZE (VERBOSE, SKIP_LOCKED) does_not_exist;
+
+-- SKIP_LOCKED option
+VACUUM (SKIP_LOCKED) vactst;
+VACUUM (SKIP_LOCKED, FULL) vactst;
+ANALYZE (SKIP_LOCKED) vactst;
 
 DROP TABLE vaccluster;
 DROP TABLE vactst;