Introduce IndexAM fields for parallel vacuum.

Introduce new fields amusemaintenanceworkmem and amparallelvacuumoptions
in IndexAmRoutine for parallel vacuum.  The amusemaintenanceworkmem tells
whether a particular IndexAM uses maintenance_work_mem or not.  This will
help in controlling the memory used by individual workers as otherwise,
each worker can consume memory equal to maintenance_work_mem.  The
amparallelvacuumoptions tell whether a particular IndexAM participates in
a parallel vacuum and if so in which phase (bulkdelete, vacuumcleanup) of
vacuum.

Author: Masahiko Sawada and Amit Kapila
Reviewed-by: Dilip Kumar, Amit Kapila, Tomas Vondra and Robert Haas
Discussion:
https://postgr.es/m/CAD21AoDTPMgzSkV4E3SFo1CH_x50bf5PqZFQf4jmqjk-C03BWg@mail.gmail.com
https://postgr.es/m/CAA4eK1LmcD5aPogzwim5Nn58Ki+74a6Edghx4Wd8hAskvHaq5A@mail.gmail.com

contrib/bloom/blutils.c

@@ -18,6 +18,7 @@
 #include "access/reloptions.h"
 #include "bloom.h"
 #include "catalog/index.h"
+#include "commands/vacuum.h"
 #include "miscadmin.h"
 #include "storage/bufmgr.h"
 #include "storage/freespace.h"
@@ -121,6 +122,9 @@ blhandler(PG_FUNCTION_ARGS)
 	amroutine->ampredlocks = false;
 	amroutine->amcanparallel = false;
 	amroutine->amcaninclude = false;
+	amroutine->amusemaintenanceworkmem = false;
+	amroutine->amparallelvacuumoptions =
+		VACUUM_OPTION_PARALLEL_BULKDEL | VACUUM_OPTION_PARALLEL_CLEANUP;
 	amroutine->amkeytype = InvalidOid;
 
 	amroutine->ambuild = blbuild;

doc/src/sgml/indexam.sgml

@@ -122,6 +122,10 @@ typedef struct IndexAmRoutine
     bool        amcanparallel;
     /* does AM support columns included with clause INCLUDE? */
     bool        amcaninclude;
+    /* does AM use maintenance_work_mem? */
+    bool        amusemaintenanceworkmem;
+    /* OR of parallel vacuum flags */
+    uint8       amparallelvacuumoptions;
     /* type of data stored in index, or InvalidOid if variable */
     Oid         amkeytype;
 

src/backend/access/brin/brin.c

@@ -27,6 +27,7 @@
 #include "access/xloginsert.h"
 #include "catalog/index.h"
 #include "catalog/pg_am.h"
+#include "commands/vacuum.h"
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "postmaster/autovacuum.h"
@@ -101,6 +102,9 @@ brinhandler(PG_FUNCTION_ARGS)
 	amroutine->ampredlocks = false;
 	amroutine->amcanparallel = false;
 	amroutine->amcaninclude = false;
+	amroutine->amusemaintenanceworkmem = false;
+	amroutine->amparallelvacuumoptions =
+		VACUUM_OPTION_PARALLEL_CLEANUP;
 	amroutine->amkeytype = InvalidOid;
 
 	amroutine->ambuild = brinbuild;

src/backend/access/gin/ginutil.c

@@ -20,6 +20,7 @@
 #include "access/xloginsert.h"
 #include "catalog/pg_collation.h"
 #include "catalog/pg_type.h"
+#include "commands/vacuum.h"
 #include "miscadmin.h"
 #include "storage/indexfsm.h"
 #include "storage/lmgr.h"
@@ -53,6 +54,9 @@ ginhandler(PG_FUNCTION_ARGS)
 	amroutine->ampredlocks = true;
 	amroutine->amcanparallel = false;
 	amroutine->amcaninclude = false;
+	amroutine->amusemaintenanceworkmem = true;
+	amroutine->amparallelvacuumoptions =
+		VACUUM_OPTION_PARALLEL_BULKDEL | VACUUM_OPTION_PARALLEL_CLEANUP;
 	amroutine->amkeytype = InvalidOid;
 
 	amroutine->ambuild = ginbuild;

src/backend/access/gist/gist.c

@@ -17,6 +17,7 @@
 #include "access/gist_private.h"
 #include "access/gistscan.h"
 #include "catalog/pg_collation.h"
+#include "commands/vacuum.h"
 #include "miscadmin.h"
 #include "nodes/execnodes.h"
 #include "storage/lmgr.h"
@@ -74,6 +75,9 @@ gisthandler(PG_FUNCTION_ARGS)
 	amroutine->ampredlocks = true;
 	amroutine->amcanparallel = false;
 	amroutine->amcaninclude = true;
+	amroutine->amusemaintenanceworkmem = false;
+	amroutine->amparallelvacuumoptions =
+		VACUUM_OPTION_PARALLEL_BULKDEL | VACUUM_OPTION_PARALLEL_COND_CLEANUP;
 	amroutine->amkeytype = InvalidOid;
 
 	amroutine->ambuild = gistbuild;

src/backend/access/hash/hash.c

@@ -72,6 +72,9 @@ hashhandler(PG_FUNCTION_ARGS)
 	amroutine->ampredlocks = true;
 	amroutine->amcanparallel = false;
 	amroutine->amcaninclude = false;
+	amroutine->amusemaintenanceworkmem = false;
+	amroutine->amparallelvacuumoptions =
+		VACUUM_OPTION_PARALLEL_BULKDEL;
 	amroutine->amkeytype = INT4OID;
 
 	amroutine->ambuild = hashbuild;

src/backend/access/nbtree/nbtree.c

@@ -121,6 +121,9 @@ bthandler(PG_FUNCTION_ARGS)
 	amroutine->ampredlocks = true;
 	amroutine->amcanparallel = true;
 	amroutine->amcaninclude = true;
+	amroutine->amusemaintenanceworkmem = false;
+	amroutine->amparallelvacuumoptions =
+		VACUUM_OPTION_PARALLEL_BULKDEL | VACUUM_OPTION_PARALLEL_COND_CLEANUP;
 	amroutine->amkeytype = InvalidOid;
 
 	amroutine->ambuild = btbuild;

src/backend/access/spgist/spgutils.c

@@ -22,6 +22,7 @@
 #include "access/transam.h"
 #include "access/xact.h"
 #include "catalog/pg_amop.h"
+#include "commands/vacuum.h"
 #include "storage/bufmgr.h"
 #include "storage/indexfsm.h"
 #include "storage/lmgr.h"
@@ -56,6 +57,9 @@ spghandler(PG_FUNCTION_ARGS)
 	amroutine->ampredlocks = false;
 	amroutine->amcanparallel = false;
 	amroutine->amcaninclude = false;
+	amroutine->amusemaintenanceworkmem = false;
+	amroutine->amparallelvacuumoptions =
+		VACUUM_OPTION_PARALLEL_BULKDEL | VACUUM_OPTION_PARALLEL_COND_CLEANUP;
 	amroutine->amkeytype = InvalidOid;
 
 	amroutine->ambuild = spgbuild;

src/include/access/amapi.h

@@ -197,6 +197,10 @@ typedef struct IndexAmRoutine
 	bool		amcanparallel;
 	/* does AM support columns included with clause INCLUDE? */
 	bool		amcaninclude;
+	/* does AM use maintenance_work_mem? */
+	bool		amusemaintenanceworkmem;
+	/* OR of parallel vacuum flags.  See vacuum.h for flags. */
+	uint8		amparallelvacuumoptions;
 	/* type of data stored in index, or InvalidOid if variable */
 	Oid			amkeytype;
 

src/include/commands/vacuum.h

@@ -23,6 +23,44 @@
 #include "storage/lock.h"
 #include "utils/relcache.h"
 
+/*
+ * Flags for amparallelvacuumoptions to control the participation of bulkdelete
+ * and vacuumcleanup in parallel vacuum.
+ */
+
+/*
+ * Both bulkdelete and vacuumcleanup are disabled by default.  This will be
+ * used by IndexAM's that don't want to or cannot participate in parallel
+ * vacuum.  For example, if an index AM doesn't have a way to communicate the
+ * index statistics allocated by the first ambulkdelete call to the subsequent
+ * ones until amvacuumcleanup, the index AM cannot participate in parallel
+ * vacuum.
+ */
+#define VACUUM_OPTION_NO_PARALLEL			0
+
+/*
+ * bulkdelete can be performed in parallel.  This option can be used by
+ * IndexAm's that need to scan the index to delete the tuples.
+ */
+#define VACUUM_OPTION_PARALLEL_BULKDEL		(1 << 0)
+
+/*
+ * vacuumcleanup can be performed in parallel if bulkdelete is not performed
+ * yet.  This will be used by IndexAM's that can scan the index if the
+ * bulkdelete is not performed.
+ */
+#define VACUUM_OPTION_PARALLEL_COND_CLEANUP	(1 << 1)
+
+/*
+ * vacuumcleanup can be performed in parallel even if bulkdelete has already
+ * processed the index.  This will be used by IndexAM's that scan the index
+ * during the cleanup phase of index irrespective of whether the index is
+ * already scanned or not during bulkdelete phase.
+ */
+#define VACUUM_OPTION_PARALLEL_CLEANUP		(1 << 2)
+
+/* value for checking vacuum flags */
+#define VACUUM_OPTION_MAX_VALID_VALUE		((1 << 3) - 1)
 
 /*----------
  * ANALYZE builds one of these structs for each attribute (column) that is

src/test/modules/dummy_index_am/dummy_index_am.c

@@ -16,6 +16,7 @@
 #include "access/amapi.h"
 #include "access/reloptions.h"
 #include "catalog/index.h"
+#include "commands/vacuum.h"
 #include "nodes/pathnodes.h"
 #include "utils/guc.h"
 #include "utils/rel.h"
@@ -294,6 +295,8 @@ dihandler(PG_FUNCTION_ARGS)
 	amroutine->ampredlocks = false;
 	amroutine->amcanparallel = false;
 	amroutine->amcaninclude = false;
+	amroutine->amusemaintenanceworkmem = false;
+	amroutine->amparallelvacuumoptions = VACUUM_OPTION_NO_PARALLEL;
 	amroutine->amkeytype = InvalidOid;
 
 	amroutine->ambuild = dibuild;