Fix typo in freeze_table_age implementation

The original code used freeze_min_age instead of freeze_table_age.  The
main consequence of this mistake is that lowering freeze_min_age would
cause full-table scans to occur much more frequently, which causes
serious issues because the number of writes required is much larger.
That feature (freeze_min_age) is supposed to affect only how soon tuples
are frozen; some pages should still be skipped due to the visibility
map.

Backpatch to 8.4, where the freeze_table_age feature was introduced.

Report and patch from Andres Freund

diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index 2569f28b80cdad53aa4abd2810ec66c7a9a9d310..dbf10401b66fa6a133202cce499b0fac0d4b3cf4 100644 (file)
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -665,7 +665,7 @@ vacuum_set_xid_limits(int freeze_min_age,
                 * VACUUM schedule, the nightly VACUUM gets a chance to freeze tuples
                 * before anti-wraparound autovacuum is launched.
                 */
-               freezetable = freeze_min_age;
+               freezetable = freeze_table_age;
                if (freezetable < 0)
                        freezetable = vacuum_freeze_table_age;
                freezetable = Min(freezetable, autovacuum_freeze_max_age * 0.95);