postgresql/contrib/pgstattuple/expected/pgstattuple.out
Teodor Sigaev 857f9c36cd 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
2018-04-04 19:29:00 +03:00

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CREATE EXTENSION pgstattuple;
--
-- It's difficult to come up with platform-independent test cases for
-- the pgstattuple functions, but the results for empty tables and
-- indexes should be that.
--
create table test (a int primary key, b int[]);
select * from pgstattuple('test');
table_len | tuple_count | tuple_len | tuple_percent | dead_tuple_count | dead_tuple_len | dead_tuple_percent | free_space | free_percent
-----------+-------------+-----------+---------------+------------------+----------------+--------------------+------------+--------------
0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
(1 row)
select * from pgstattuple('test'::text);
table_len | tuple_count | tuple_len | tuple_percent | dead_tuple_count | dead_tuple_len | dead_tuple_percent | free_space | free_percent
-----------+-------------+-----------+---------------+------------------+----------------+--------------------+------------+--------------
0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
(1 row)
select * from pgstattuple('test'::name);
table_len | tuple_count | tuple_len | tuple_percent | dead_tuple_count | dead_tuple_len | dead_tuple_percent | free_space | free_percent
-----------+-------------+-----------+---------------+------------------+----------------+--------------------+------------+--------------
0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
(1 row)
select * from pgstattuple('test'::regclass);
table_len | tuple_count | tuple_len | tuple_percent | dead_tuple_count | dead_tuple_len | dead_tuple_percent | free_space | free_percent
-----------+-------------+-----------+---------------+------------------+----------------+--------------------+------------+--------------
0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
(1 row)
select pgstattuple(oid) from pg_class where relname = 'test';
pgstattuple
---------------------
(0,0,0,0,0,0,0,0,0)
(1 row)
select pgstattuple(relname) from pg_class where relname = 'test';
pgstattuple
---------------------
(0,0,0,0,0,0,0,0,0)
(1 row)
select version, tree_level,
index_size / current_setting('block_size')::int as index_size,
root_block_no, internal_pages, leaf_pages, empty_pages, deleted_pages,
avg_leaf_density, leaf_fragmentation
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
---------+------------+------------+---------------+----------------+------------+-------------+---------------+------------------+--------------------
3 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | NaN | NaN
(1 row)
select version, tree_level,
index_size / current_setting('block_size')::int as index_size,
root_block_no, internal_pages, leaf_pages, empty_pages, deleted_pages,
avg_leaf_density, leaf_fragmentation
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
---------+------------+------------+---------------+----------------+------------+-------------+---------------+------------------+--------------------
3 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | NaN | NaN
(1 row)
select version, tree_level,
index_size / current_setting('block_size')::int as index_size,
root_block_no, internal_pages, leaf_pages, empty_pages, deleted_pages,
avg_leaf_density, leaf_fragmentation
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
---------+------------+------------+---------------+----------------+------------+-------------+---------------+------------------+--------------------
3 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | NaN | NaN
(1 row)
select version, tree_level,
index_size / current_setting('block_size')::int as index_size,
root_block_no, internal_pages, leaf_pages, empty_pages, deleted_pages,
avg_leaf_density, leaf_fragmentation
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
---------+------------+------------+---------------+----------------+------------+-------------+---------------+------------------+--------------------
3 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | NaN | NaN
(1 row)
select pg_relpages('test');
pg_relpages
-------------
0
(1 row)
select pg_relpages('test_pkey');
pg_relpages
-------------
1
(1 row)
select pg_relpages('test_pkey'::text);
pg_relpages
-------------
1
(1 row)
select pg_relpages('test_pkey'::name);
pg_relpages
-------------
1
(1 row)
select pg_relpages('test_pkey'::regclass);
pg_relpages
-------------
1
(1 row)
select pg_relpages(oid) from pg_class where relname = 'test_pkey';
pg_relpages
-------------
1
(1 row)
select pg_relpages(relname) from pg_class where relname = 'test_pkey';
pg_relpages
-------------
1
(1 row)
create index test_ginidx on test using gin (b);
select * from pgstatginindex('test_ginidx');
version | pending_pages | pending_tuples
---------+---------------+----------------
2 | 0 | 0
(1 row)
create index test_hashidx on test using hash (b);
select * from pgstathashindex('test_hashidx');
version | bucket_pages | overflow_pages | bitmap_pages | unused_pages | live_items | dead_items | free_percent
---------+--------------+----------------+--------------+--------------+------------+------------+--------------
4 | 4 | 0 | 1 | 0 | 0 | 0 | 100
(1 row)
-- these should error with the wrong type
select pgstatginindex('test_pkey');
ERROR: relation "test_pkey" is not a GIN index
select pgstathashindex('test_pkey');
ERROR: relation "test_pkey" is not a HASH index
select pgstatindex('test_ginidx');
ERROR: relation "test_ginidx" is not a btree index
select pgstathashindex('test_ginidx');
ERROR: relation "test_ginidx" is not a HASH index
select pgstatindex('test_hashidx');
ERROR: relation "test_hashidx" is not a btree index
select pgstatginindex('test_hashidx');
ERROR: relation "test_hashidx" is not a GIN index
-- check that using any of these functions with unsupported relations will fail
create table test_partitioned (a int) partition by range (a);
-- these should all fail
select pgstattuple('test_partitioned');
ERROR: "test_partitioned" (partitioned table) is not supported
select pgstattuple_approx('test_partitioned');
ERROR: "test_partitioned" is not a table or materialized view
select pg_relpages('test_partitioned');
ERROR: "test_partitioned" is not a table, index, materialized view, sequence, or TOAST table
select pgstatindex('test_partitioned');
ERROR: relation "test_partitioned" is not a btree index
select pgstatginindex('test_partitioned');
ERROR: relation "test_partitioned" is not a GIN index
select pgstathashindex('test_partitioned');
ERROR: "test_partitioned" is not an index
create view test_view as select 1;
-- these should all fail
select pgstattuple('test_view');
ERROR: "test_view" (view) is not supported
select pgstattuple_approx('test_view');
ERROR: "test_view" is not a table or materialized view
select pg_relpages('test_view');
ERROR: "test_view" is not a table, index, materialized view, sequence, or TOAST table
select pgstatindex('test_view');
ERROR: relation "test_view" is not a btree index
select pgstatginindex('test_view');
ERROR: relation "test_view" is not a GIN index
select pgstathashindex('test_view');
ERROR: "test_view" is not an index
create foreign data wrapper dummy;
create server dummy_server foreign data wrapper dummy;
create foreign table test_foreign_table () server dummy_server;
-- these should all fail
select pgstattuple('test_foreign_table');
ERROR: "test_foreign_table" (foreign table) is not supported
select pgstattuple_approx('test_foreign_table');
ERROR: "test_foreign_table" is not a table or materialized view
select pg_relpages('test_foreign_table');
ERROR: "test_foreign_table" is not a table, index, materialized view, sequence, or TOAST table
select pgstatindex('test_foreign_table');
ERROR: relation "test_foreign_table" is not a btree index
select pgstatginindex('test_foreign_table');
ERROR: relation "test_foreign_table" is not a GIN index
select pgstathashindex('test_foreign_table');
ERROR: "test_foreign_table" is not an index
-- a partition of a partitioned table should work though
create table test_partition partition of test_partitioned for values from (1) to (100);
select pgstattuple('test_partition');
pgstattuple
---------------------
(0,0,0,0,0,0,0,0,0)
(1 row)
select pgstattuple_approx('test_partition');
pgstattuple_approx
-----------------------
(0,0,0,0,0,0,0,0,0,0)
(1 row)
select pg_relpages('test_partition');
pg_relpages
-------------
0
(1 row)
-- not for the index calls though, of course
select pgstatindex('test_partition');
ERROR: relation "test_partition" is not a btree index
select pgstatginindex('test_partition');
ERROR: relation "test_partition" is not a GIN index
select pgstathashindex('test_partition');
ERROR: "test_partition" is not an index
-- an actual index of a partitioned table should work though
create index test_partition_idx on test_partition(a);
create index test_partition_hash_idx on test_partition using hash (a);
-- these should work
select pgstatindex('test_partition_idx');
pgstatindex
------------------------------
(3,0,8192,0,0,0,0,0,NaN,NaN)
(1 row)
select pgstathashindex('test_partition_hash_idx');
pgstathashindex
---------------------
(4,8,0,1,0,0,0,100)
(1 row)
drop table test_partitioned;
drop view test_view;
drop foreign table test_foreign_table;
drop server dummy_server;
drop foreign data wrapper dummy;