Skip full index scan during cleanup of B-tree indexes when possible

Vacuum of index consists from two stages: multiple (zero of more) ambulkdelete
calls and one amvacuumcleanup call. When workload on particular table
is append-only, then autovacuum isn't intended to touch this table. However,
user may run vacuum manually in order to fill visibility map and get benefits
of index-only scans. Then ambulkdelete wouldn't be called for indexes
of such table (because no heap tuples were deleted), only amvacuumcleanup would
be called In this case, amvacuumcleanup would perform full index scan for
two objectives: put recyclable pages into free space map and update index
statistics.

This patch allows btvacuumclanup to skip full index scan when two conditions
are satisfied: no pages are going to be put into free space map and index
statistics isn't stalled. In order to check first condition, we store
oldest btpo_xact in the meta-page. When it's precedes RecentGlobalXmin, then
there are some recyclable pages. In order to check second condition we store
number of heap tuples observed during previous full index scan by cleanup.
If fraction of newly inserted tuples is less than
vacuum_cleanup_index_scale_factor, then statistics isn't considered to be
stalled. vacuum_cleanup_index_scale_factor can be defined as both reloption and GUC (default).

This patch bumps B-tree meta-page version. Upgrade of meta-page is performed
"on the fly": during VACUUM meta-page is rewritten with new version. No special
handling in pg_upgrade is required.

Author: Masahiko Sawada, Alexander Korotkov
Review by: Peter Geoghegan, Kyotaro Horiguchi, Alexander Korotkov, Yura Sokolov
Discussion: https://www.postgresql.org/message-id/flat/CAD21AoAX+d2oD_nrd9O2YkpzHaFr=uQeGr9s1rKC3O4ENc568g@mail.gmail.com

7 files changed, 51 insertions, 18 deletions

diff --git a/contrib/amcheck/verify_nbtree.c b/contrib/amcheck/verify_nbtree.c
index a15fe21933b..52aa633056b 100644
--- a/contrib/amcheck/verify_nbtree.c
+++ b/contrib/amcheck/verify_nbtree.c
@@ -1500,12 +1500,14 @@ palloc_btree_page(BtreeCheckState *state, BlockNumber blocknum)
 					 errmsg("index \"%s\" meta page is corrupt",
 							RelationGetRelationName(state->rel))));
 
-		if (metad->btm_version != BTREE_VERSION)
+		if (metad->btm_version < BTREE_MIN_VERSION ||
+			metad->btm_version > BTREE_VERSION)
 			ereport(ERROR,
 					(errcode(ERRCODE_INDEX_CORRUPTED),
-					 errmsg("version mismatch in index \"%s\": file version %d, code version %d",
+					 errmsg("version mismatch in index \"%s\": file version %d, "
+							"current version %d, minimal supported version %d",
 							RelationGetRelationName(state->rel),
-							metad->btm_version, BTREE_VERSION)));
+							metad->btm_version, BTREE_VERSION, BTREE_MIN_VERSION)));
 	}
 
 	/*
diff --git a/contrib/pageinspect/Makefile b/contrib/pageinspect/Makefile
index 0a3cbeeb108..e5a581f141b 100644
--- a/contrib/pageinspect/Makefile
+++ b/contrib/pageinspect/Makefile
@@ -5,7 +5,8 @@ OBJS		= rawpage.o heapfuncs.o btreefuncs.o fsmfuncs.o \
 		  brinfuncs.o ginfuncs.o hashfuncs.o $(WIN32RES)
 
 EXTENSION = pageinspect
-DATA = pageinspect--1.5.sql pageinspect--1.5--1.6.sql \
+DATA =  pageinspect--1.6--1.7.sql \
+	pageinspect--1.5.sql pageinspect--1.5--1.6.sql \
 	pageinspect--1.4--1.5.sql pageinspect--1.3--1.4.sql \
 	pageinspect--1.2--1.3.sql pageinspect--1.1--1.2.sql \
 	pageinspect--1.0--1.1.sql pageinspect--unpackaged--1.0.sql
diff --git a/contrib/pageinspect/btreefuncs.c b/contrib/pageinspect/btreefuncs.c
index 4f834676ea2..51336537919 100644
--- a/contrib/pageinspect/btreefuncs.c
+++ b/contrib/pageinspect/btreefuncs.c
@@ -511,7 +511,7 @@ bt_metap(PG_FUNCTION_ARGS)
 	BTMetaPageData *metad;
 	TupleDesc	tupleDesc;
 	int			j;
-	char	   *values[6];
+	char	   *values[8];
 	Buffer		buffer;
 	Page		page;
 	HeapTuple	tuple;
@@ -555,6 +555,8 @@ bt_metap(PG_FUNCTION_ARGS)
 	values[j++] = psprintf("%d", metad->btm_level);
 	values[j++] = psprintf("%d", metad->btm_fastroot);
 	values[j++] = psprintf("%d", metad->btm_fastlevel);
+	values[j++] = psprintf("%u", metad->btm_oldest_btpo_xact);
+	values[j++] = psprintf("%lf", metad->btm_last_cleanup_num_heap_tuples);
 
 	tuple = BuildTupleFromCStrings(TupleDescGetAttInMetadata(tupleDesc),
 								   values);
diff --git a/contrib/pageinspect/expected/btree.out b/contrib/pageinspect/expected/btree.out
index 67b103add3f..2aaa4df53b1 100644
--- a/contrib/pageinspect/expected/btree.out
+++ b/contrib/pageinspect/expected/btree.out
@@ -3,13 +3,15 @@ INSERT INTO test1 VALUES (72057594037927937, 'text');
 CREATE INDEX test1_a_idx ON test1 USING btree (a);
 \x
 SELECT * FROM bt_metap('test1_a_idx');
--[ RECORD 1 ]-----
-magic     | 340322
-version   | 2
-root      | 1
-level     | 0
-fastroot  | 1
-fastlevel | 0
+-[ RECORD 1 ]-----------+-------
+magic                   | 340322
+version                 | 3
+root                    | 1
+level                   | 0
+fastroot                | 1
+fastlevel               | 0
+oldest_xact             | 0
+last_cleanup_num_tuples | -1
 
 SELECT * FROM bt_page_stats('test1_a_idx', 0);
 ERROR:  block 0 is a meta page
diff --git a/contrib/pageinspect/pageinspect--1.6--1.7.sql b/contrib/pageinspect/pageinspect--1.6--1.7.sql
new file mode 100644
index 00000000000..2433a21af27
--- /dev/null
+++ b/contrib/pageinspect/pageinspect--1.6--1.7.sql
@@ -0,0 +1,26 @@
+/* contrib/pageinspect/pageinspect--1.6--1.7.sql */
+
+-- complain if script is sourced in psql, rather than via ALTER EXTENSION
+\echo Use "ALTER EXTENSION pageinspect UPDATE TO '1.7'" to load this file. \quit
+
+--
+-- bt_metap()
+--
+DROP FUNCTION bt_metap(IN relname text,
+    OUT magic int4,
+    OUT version int4,
+    OUT root int4,
+    OUT level int4,
+    OUT fastroot int4,
+    OUT fastlevel int4);
+CREATE FUNCTION bt_metap(IN relname text,
+    OUT magic int4,
+    OUT version int4,
+    OUT root int4,
+    OUT level int4,
+    OUT fastroot int4,
+    OUT fastlevel int4,
+    OUT oldest_xact int4,
+    OUT last_cleanup_num_tuples real)
+AS 'MODULE_PATHNAME', 'bt_metap'
+LANGUAGE C STRICT PARALLEL SAFE;
diff --git a/contrib/pageinspect/pageinspect.control b/contrib/pageinspect/pageinspect.control
index 1a61c9f5ad3..dcfc61f22dc 100644
--- a/contrib/pageinspect/pageinspect.control
+++ b/contrib/pageinspect/pageinspect.control
@@ -1,5 +1,5 @@
 # pageinspect extension
 comment = 'inspect the contents of database pages at a low level'
-default_version = '1.6'
+default_version = '1.7'
 module_pathname = '$libdir/pageinspect'
 relocatable = true
diff --git a/contrib/pgstattuple/expected/pgstattuple.out b/contrib/pgstattuple/expected/pgstattuple.out
index 20b5585d03a..a7087f6d457 100644
--- a/contrib/pgstattuple/expected/pgstattuple.out
+++ b/contrib/pgstattuple/expected/pgstattuple.out
@@ -48,7 +48,7 @@ select version, tree_level,
     from pgstatindex('test_pkey');
  version | tree_level | index_size | root_block_no | internal_pages | leaf_pages | empty_pages | deleted_pages | avg_leaf_density | leaf_fragmentation 
 ---------+------------+------------+---------------+----------------+------------+-------------+---------------+------------------+--------------------
-       2 |          0 |          1 |             0 |              0 |          0 |           0 |             0 |              NaN |                NaN
+       3 |          0 |          1 |             0 |              0 |          0 |           0 |             0 |              NaN |                NaN
 (1 row)
 
 select version, tree_level,
@@ -58,7 +58,7 @@ select version, tree_level,
     from pgstatindex('test_pkey'::text);
  version | tree_level | index_size | root_block_no | internal_pages | leaf_pages | empty_pages | deleted_pages | avg_leaf_density | leaf_fragmentation 
 ---------+------------+------------+---------------+----------------+------------+-------------+---------------+------------------+--------------------
-       2 |          0 |          1 |             0 |              0 |          0 |           0 |             0 |              NaN |                NaN
+       3 |          0 |          1 |             0 |              0 |          0 |           0 |             0 |              NaN |                NaN
 (1 row)
 
 select version, tree_level,
@@ -68,7 +68,7 @@ select version, tree_level,
     from pgstatindex('test_pkey'::name);
  version | tree_level | index_size | root_block_no | internal_pages | leaf_pages | empty_pages | deleted_pages | avg_leaf_density | leaf_fragmentation 
 ---------+------------+------------+---------------+----------------+------------+-------------+---------------+------------------+--------------------
-       2 |          0 |          1 |             0 |              0 |          0 |           0 |             0 |              NaN |                NaN
+       3 |          0 |          1 |             0 |              0 |          0 |           0 |             0 |              NaN |                NaN
 (1 row)
 
 select version, tree_level,
@@ -78,7 +78,7 @@ select version, tree_level,
     from pgstatindex('test_pkey'::regclass);
  version | tree_level | index_size | root_block_no | internal_pages | leaf_pages | empty_pages | deleted_pages | avg_leaf_density | leaf_fragmentation 
 ---------+------------+------------+---------------+----------------+------------+-------------+---------------+------------------+--------------------
-       2 |          0 |          1 |             0 |              0 |          0 |           0 |             0 |              NaN |                NaN
+       3 |          0 |          1 |             0 |              0 |          0 |           0 |             0 |              NaN |                NaN
 (1 row)
 
 select pg_relpages('test');
@@ -229,7 +229,7 @@ create index test_partition_hash_idx on test_partition using hash (a);
 select pgstatindex('test_partition_idx');
          pgstatindex          
 ------------------------------
- (2,0,8192,0,0,0,0,0,NaN,NaN)
+ (3,0,8192,0,0,0,0,0,NaN,NaN)
 (1 row)
 
 select pgstathashindex('test_partition_hash_idx');