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| author | Peter Geoghegan <pg@bowt.ie> | 2022-04-03 09:57:21 -0700 |
|---|---|---|
| committer | Peter Geoghegan <pg@bowt.ie> | 2022-04-03 09:57:21 -0700 |
| commit | 0b018fabaaba77e39539ce7eb71e34a90ceb0825 (patch) | |
| tree | a4b8ae23a9e20cf23460d3ba811c67a039f605e4 /src/backend/commands/cluster.c | |
| parent | 05023a237c059c840380817abf079a9282a227b7 (diff) | |
| download | postgresql-0b018fabaaba77e39539ce7eb71e34a90ceb0825.tar.gz postgresql-0b018fabaaba77e39539ce7eb71e34a90ceb0825.zip | |
Set relfrozenxid to oldest extant XID seen by VACUUM.
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.com
Diffstat (limited to 'src/backend/commands/cluster.c')
| -rw-r--r-- | src/backend/commands/cluster.c | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/src/backend/commands/cluster.c b/src/backend/commands/cluster.c index cd19e35319e..322d6bb2f18 100644 --- a/src/backend/commands/cluster.c +++ b/src/backend/commands/cluster.c @@ -806,9 +806,10 @@ copy_table_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex, bool verbose, Form_pg_class relform; TupleDesc oldTupDesc PG_USED_FOR_ASSERTS_ONLY; TupleDesc newTupDesc PG_USED_FOR_ASSERTS_ONLY; - TransactionId OldestXmin; - TransactionId FreezeXid; - MultiXactId MultiXactCutoff; + TransactionId OldestXmin, + FreezeXid; + MultiXactId OldestMxact, + MultiXactCutoff; bool use_sort; double num_tuples = 0, tups_vacuumed = 0, @@ -896,8 +897,8 @@ copy_table_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex, bool verbose, * Since we're going to rewrite the whole table anyway, there's no reason * not to be aggressive about this. */ - vacuum_set_xid_limits(OldHeap, 0, 0, 0, 0, - &OldestXmin, &FreezeXid, &MultiXactCutoff); + vacuum_set_xid_limits(OldHeap, 0, 0, 0, 0, &OldestXmin, &OldestMxact, + &FreezeXid, &MultiXactCutoff); /* * FreezeXid will become the table's new relfrozenxid, and that mustn't go |