mirror of https://github.com/postgres/postgres
When VACUUM set relfrozenxid before now, it set it to whatever value was used to determine which tuples to freeze -- the FreezeLimit cutoff. This approach was very naive. The relfrozenxid invariant only requires that new relfrozenxid values be <= the oldest extant XID remaining in the table (at the point that the VACUUM operation ends), which in general might be much more recent than FreezeLimit. VACUUM now carefully tracks the oldest remaining XID/MultiXactId as it goes (the oldest remaining values _after_ lazy_scan_prune processing). The final values are set as the table's new relfrozenxid and new relminmxid in pg_class at the end of each VACUUM. The oldest XID might come from a tuple's xmin, xmax, or xvac fields. It might even come from one of the table's remaining MultiXacts. Final relfrozenxid values must still be >= FreezeLimit in an aggressive VACUUM (FreezeLimit still acts as a lower bound on the final value that aggressive VACUUM can set relfrozenxid to). Since standard VACUUMs still make no guarantees about advancing relfrozenxid, they might as well set relfrozenxid to a value from well before FreezeLimit when the opportunity presents itself. In general standard VACUUMs may now set relfrozenxid to any value > the original relfrozenxid and <= OldestXmin. Credit for the general idea of using the oldest extant XID to set pg_class.relfrozenxid at the end of VACUUM goes to Andres Freund. Author: Peter Geoghegan <pg@bowt.ie> Reviewed-By: Andres Freund <andres@anarazel.de> Reviewed-By: Robert Haas <robertmhaas@gmail.com> Discussion: https://postgr.es/m/CAH2-WzkymFbz6D_vL+jmqSn_5q1wsFvFrE+37yLgL_Rkfd6Gzg@mail.gmail.compull/81/head
Peter Geoghegan
4 years ago
parent
05023a237c
commit
0b018fabaa
@ -0,0 +1,189 @@ |
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Parsed test spec with 4 sessions |
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|
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starting permutation: vacuumer_pg_class_stats dml_insert vacuumer_nonaggressive_vacuum vacuumer_pg_class_stats |
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step vacuumer_pg_class_stats: |
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SELECT relpages, reltuples FROM pg_class WHERE oid = 'smalltbl'::regclass; |
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|
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relpages|reltuples |
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--------+--------- |
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1| 20 |
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(1 row) |
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|
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step dml_insert: |
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INSERT INTO smalltbl SELECT max(id) + 1 FROM smalltbl; |
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|
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step vacuumer_nonaggressive_vacuum: |
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VACUUM smalltbl; |
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|
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step vacuumer_pg_class_stats: |
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SELECT relpages, reltuples FROM pg_class WHERE oid = 'smalltbl'::regclass; |
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|
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relpages|reltuples |
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--------+--------- |
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1| 21 |
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(1 row) |
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|
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|
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starting permutation: vacuumer_pg_class_stats dml_insert pinholder_cursor vacuumer_nonaggressive_vacuum vacuumer_pg_class_stats pinholder_commit |
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step vacuumer_pg_class_stats: |
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SELECT relpages, reltuples FROM pg_class WHERE oid = 'smalltbl'::regclass; |
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|
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relpages|reltuples |
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--------+--------- |
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1| 20 |
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(1 row) |
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|
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step dml_insert: |
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INSERT INTO smalltbl SELECT max(id) + 1 FROM smalltbl; |
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|
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step pinholder_cursor: |
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BEGIN; |
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DECLARE c1 CURSOR FOR SELECT 1 AS dummy FROM smalltbl; |
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FETCH NEXT FROM c1; |
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|
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dummy |
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----- |
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1 |
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(1 row) |
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|
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step vacuumer_nonaggressive_vacuum: |
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VACUUM smalltbl; |
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|
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step vacuumer_pg_class_stats: |
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SELECT relpages, reltuples FROM pg_class WHERE oid = 'smalltbl'::regclass; |
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|
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relpages|reltuples |
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--------+--------- |
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1| 21 |
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(1 row) |
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|
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step pinholder_commit: |
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COMMIT; |
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|
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|
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starting permutation: vacuumer_pg_class_stats pinholder_cursor dml_insert dml_delete dml_insert vacuumer_nonaggressive_vacuum vacuumer_pg_class_stats pinholder_commit |
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step vacuumer_pg_class_stats: |
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SELECT relpages, reltuples FROM pg_class WHERE oid = 'smalltbl'::regclass; |
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|
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relpages|reltuples |
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--------+--------- |
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1| 20 |
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(1 row) |
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|
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step pinholder_cursor: |
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BEGIN; |
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DECLARE c1 CURSOR FOR SELECT 1 AS dummy FROM smalltbl; |
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FETCH NEXT FROM c1; |
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|
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dummy |
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----- |
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1 |
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(1 row) |
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|
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step dml_insert: |
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INSERT INTO smalltbl SELECT max(id) + 1 FROM smalltbl; |
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|
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step dml_delete: |
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DELETE FROM smalltbl WHERE id = (SELECT min(id) FROM smalltbl); |
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|
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step dml_insert: |
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INSERT INTO smalltbl SELECT max(id) + 1 FROM smalltbl; |
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|
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step vacuumer_nonaggressive_vacuum: |
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VACUUM smalltbl; |
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|
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step vacuumer_pg_class_stats: |
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SELECT relpages, reltuples FROM pg_class WHERE oid = 'smalltbl'::regclass; |
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|
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relpages|reltuples |
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--------+--------- |
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1| 21 |
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(1 row) |
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|
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step pinholder_commit: |
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COMMIT; |
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|
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|
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starting permutation: vacuumer_pg_class_stats dml_insert dml_delete pinholder_cursor dml_insert vacuumer_nonaggressive_vacuum vacuumer_pg_class_stats pinholder_commit |
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step vacuumer_pg_class_stats: |
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SELECT relpages, reltuples FROM pg_class WHERE oid = 'smalltbl'::regclass; |
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|
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relpages|reltuples |
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--------+--------- |
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1| 20 |
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(1 row) |
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|
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step dml_insert: |
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INSERT INTO smalltbl SELECT max(id) + 1 FROM smalltbl; |
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|
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step dml_delete: |
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DELETE FROM smalltbl WHERE id = (SELECT min(id) FROM smalltbl); |
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|
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step pinholder_cursor: |
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BEGIN; |
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DECLARE c1 CURSOR FOR SELECT 1 AS dummy FROM smalltbl; |
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FETCH NEXT FROM c1; |
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|
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dummy |
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----- |
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1 |
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(1 row) |
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|
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step dml_insert: |
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INSERT INTO smalltbl SELECT max(id) + 1 FROM smalltbl; |
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|
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step vacuumer_nonaggressive_vacuum: |
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VACUUM smalltbl; |
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step vacuumer_pg_class_stats: |
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SELECT relpages, reltuples FROM pg_class WHERE oid = 'smalltbl'::regclass; |
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|
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relpages|reltuples |
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--------+--------- |
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1| 21 |
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(1 row) |
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|
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step pinholder_commit: |
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COMMIT; |
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|
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|
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starting permutation: dml_begin dml_other_begin dml_key_share dml_other_key_share vacuumer_nonaggressive_vacuum pinholder_cursor dml_other_update dml_commit dml_other_commit vacuumer_nonaggressive_vacuum pinholder_commit vacuumer_nonaggressive_vacuum |
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step dml_begin: BEGIN; |
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step dml_other_begin: BEGIN; |
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step dml_key_share: SELECT id FROM smalltbl WHERE id = 3 FOR KEY SHARE; |
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id |
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-- |
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3 |
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(1 row) |
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|
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step dml_other_key_share: SELECT id FROM smalltbl WHERE id = 3 FOR KEY SHARE; |
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id |
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-- |
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3 |
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(1 row) |
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|
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step vacuumer_nonaggressive_vacuum: |
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VACUUM smalltbl; |
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|
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step pinholder_cursor: |
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BEGIN; |
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DECLARE c1 CURSOR FOR SELECT 1 AS dummy FROM smalltbl; |
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FETCH NEXT FROM c1; |
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|
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dummy |
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----- |
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1 |
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(1 row) |
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step dml_other_update: UPDATE smalltbl SET t = 'u' WHERE id = 3; |
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step dml_commit: COMMIT; |
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step dml_other_commit: COMMIT; |
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step vacuumer_nonaggressive_vacuum: |
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VACUUM smalltbl; |
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step pinholder_commit: |
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COMMIT; |
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step vacuumer_nonaggressive_vacuum: |
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VACUUM smalltbl; |
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@ -1,67 +0,0 @@ |
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Parsed test spec with 2 sessions |
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starting permutation: modify vac stats |
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step modify: |
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insert into smalltbl select max(id)+1 from smalltbl; |
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step vac: |
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vacuum smalltbl; |
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step stats: |
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select relpages, reltuples from pg_class |
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where oid='smalltbl'::regclass; |
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relpages|reltuples |
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--------+--------- |
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1| 21 |
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(1 row) |
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starting permutation: modify open fetch1 vac close stats |
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step modify: |
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insert into smalltbl select max(id)+1 from smalltbl; |
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step open: |
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begin; |
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declare c1 cursor for select 1 as dummy from smalltbl; |
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step fetch1: |
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fetch next from c1; |
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dummy |
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----- |
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1 |
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(1 row) |
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step vac: |
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vacuum smalltbl; |
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step close: |
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commit; |
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step stats: |
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select relpages, reltuples from pg_class |
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where oid='smalltbl'::regclass; |
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relpages|reltuples |
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--------+--------- |
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1| 21 |
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(1 row) |
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starting permutation: modify vac stats |
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step modify: |
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insert into smalltbl select max(id)+1 from smalltbl; |
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step vac: |
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vacuum smalltbl; |
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step stats: |
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select relpages, reltuples from pg_class |
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where oid='smalltbl'::regclass; |
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relpages|reltuples |
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--------+--------- |
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1| 21 |
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(1 row) |
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@ -0,0 +1,150 @@ |
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# Test for vacuum's reduced processing of heap pages (used for any heap page |
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# where a cleanup lock isn't immediately available) |
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# |
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# Debugging tip: Change VACUUM to VACUUM VERBOSE to get feedback on what's |
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# really going on |
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# Use name type here to avoid TOAST table: |
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setup |
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{ |
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CREATE TABLE smalltbl AS SELECT i AS id, 't'::name AS t FROM generate_series(1,20) i; |
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ALTER TABLE smalltbl SET (autovacuum_enabled = off); |
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ALTER TABLE smalltbl ADD PRIMARY KEY (id); |
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} |
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setup |
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{ |
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VACUUM ANALYZE smalltbl; |
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} |
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teardown |
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{ |
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DROP TABLE smalltbl; |
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} |
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# This session holds a pin on smalltbl's only heap page: |
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session pinholder |
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step pinholder_cursor |
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{ |
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BEGIN; |
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DECLARE c1 CURSOR FOR SELECT 1 AS dummy FROM smalltbl; |
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FETCH NEXT FROM c1; |
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} |
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step pinholder_commit |
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{ |
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COMMIT; |
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} |
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# This session inserts and deletes tuples, potentially affecting reltuples: |
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session dml |
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step dml_insert |
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{ |
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INSERT INTO smalltbl SELECT max(id) + 1 FROM smalltbl; |
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} |
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step dml_delete |
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{ |
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DELETE FROM smalltbl WHERE id = (SELECT min(id) FROM smalltbl); |
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} |
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step dml_begin { BEGIN; } |
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step dml_key_share { SELECT id FROM smalltbl WHERE id = 3 FOR KEY SHARE; } |
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step dml_commit { COMMIT; } |
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# Needed for Multixact test: |
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session dml_other |
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step dml_other_begin { BEGIN; } |
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step dml_other_key_share { SELECT id FROM smalltbl WHERE id = 3 FOR KEY SHARE; } |
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step dml_other_update { UPDATE smalltbl SET t = 'u' WHERE id = 3; } |
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step dml_other_commit { COMMIT; } |
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# This session runs non-aggressive VACUUM, but with maximally aggressive |
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# cutoffs for tuple freezing (e.g., FreezeLimit == OldestXmin): |
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session vacuumer |
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setup |
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{ |
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SET vacuum_freeze_min_age = 0; |
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SET vacuum_multixact_freeze_min_age = 0; |
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} |
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step vacuumer_nonaggressive_vacuum |
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{ |
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VACUUM smalltbl; |
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} |
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step vacuumer_pg_class_stats |
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{ |
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SELECT relpages, reltuples FROM pg_class WHERE oid = 'smalltbl'::regclass; |
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} |
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# Test VACUUM's reltuples counting mechanism. |
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# |
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# Final pg_class.reltuples should never be affected by VACUUM's inability to |
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# get a cleanup lock on any page, except to the extent that any cleanup lock |
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# contention changes the number of tuples that remain ("missed dead" tuples |
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# are counted in reltuples, much like "recently dead" tuples). |
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# Easy case: |
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permutation |
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vacuumer_pg_class_stats # Start with 20 tuples |
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dml_insert |
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vacuumer_nonaggressive_vacuum |
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vacuumer_pg_class_stats # End with 21 tuples |
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# Harder case -- count 21 tuples at the end (like last time), but with cleanup |
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# lock contention this time: |
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permutation |
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vacuumer_pg_class_stats # Start with 20 tuples |
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dml_insert |
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pinholder_cursor |
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vacuumer_nonaggressive_vacuum |
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vacuumer_pg_class_stats # End with 21 tuples |
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pinholder_commit # order doesn't matter |
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# Same as "harder case", but vary the order, and delete an inserted row: |
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permutation |
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vacuumer_pg_class_stats # Start with 20 tuples |
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pinholder_cursor |
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dml_insert |
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dml_delete |
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dml_insert |
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vacuumer_nonaggressive_vacuum |
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# reltuples is 21 here again -- "recently dead" tuple won't be included in |
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# count here: |
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vacuumer_pg_class_stats |
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pinholder_commit # order doesn't matter |
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# Same as "harder case", but initial insert and delete before cursor: |
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permutation |
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vacuumer_pg_class_stats # Start with 20 tuples |
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dml_insert |
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dml_delete |
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pinholder_cursor |
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dml_insert |
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vacuumer_nonaggressive_vacuum |
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# reltuples is 21 here again -- "missed dead" tuple ("recently dead" when |
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# concurrent activity held back VACUUM's OldestXmin) won't be included in |
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# count here: |
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vacuumer_pg_class_stats |
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pinholder_commit # order doesn't matter |
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|
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# Test VACUUM's mechanism for skipping MultiXact freezing. |
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# |
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# This provides test coverage for code paths that are only hit when we need to |
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# freeze, but inability to acquire a cleanup lock on a heap page makes |
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# freezing some XIDs/XMIDs < FreezeLimit/MultiXactCutoff impossible (without |
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# waiting for a cleanup lock, which non-aggressive VACUUM is unwilling to do). |
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permutation |
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dml_begin |
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dml_other_begin |
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dml_key_share |
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dml_other_key_share |
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# Will get cleanup lock, can't advance relminmxid yet: |
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# (though will usually advance relfrozenxid by ~2 XIDs) |
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vacuumer_nonaggressive_vacuum |
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pinholder_cursor |
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dml_other_update |
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dml_commit |
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dml_other_commit |
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# Can't cleanup lock, so still can't advance relminmxid here: |
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# (relfrozenxid held back by XIDs in MultiXact too) |
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vacuumer_nonaggressive_vacuum |
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pinholder_commit |
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# Pin was dropped, so will advance relminmxid, at long last: |
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# (ditto for relfrozenxid advancement) |
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vacuumer_nonaggressive_vacuum |
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@ -1,49 +0,0 @@ |
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# Test for vacuum's handling of reltuples when pages are skipped due |
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# to page pins. We absolutely need to avoid setting reltuples=0 in |
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# such cases, since that interferes badly with planning. |
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# |
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# Expected result for all three permutation is 21 tuples, including |
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# the second permutation. VACUUM is able to count the concurrently |
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# inserted tuple in its final reltuples, even when a cleanup lock |
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# cannot be acquired on the affected heap page. |
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setup { |
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create table smalltbl |
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as select i as id from generate_series(1,20) i; |
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alter table smalltbl set (autovacuum_enabled = off); |
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} |
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setup { |
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vacuum analyze smalltbl; |
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} |
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teardown { |
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drop table smalltbl; |
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} |
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session worker |
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step open { |
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begin; |
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declare c1 cursor for select 1 as dummy from smalltbl; |
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} |
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step fetch1 { |
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fetch next from c1; |
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} |
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step close { |
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commit; |
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} |
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step stats { |
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select relpages, reltuples from pg_class |
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where oid='smalltbl'::regclass; |
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} |
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session vacuumer |
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step vac { |
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vacuum smalltbl; |
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} |
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step modify { |
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insert into smalltbl select max(id)+1 from smalltbl; |
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} |
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permutation modify vac stats |
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permutation modify open fetch1 vac close stats |
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permutation modify vac stats |
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