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Remove some unnecessary code from multixact truncation

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With 64-bit multixact offsets, PerformMembersTruncation() doesn't need
the starting offset anymore. The 'oldestOffset' value that
TruncateMultiXact() calculates is no longer used for anything. Remove
it, and the code to calculate it.

'oldestOffset' was included in the WAL record as 'startTruncMemb',
which sounds nice if you e.g. look at the WAL with pg_waldump, but it
was also confusing because we didn't actually use the value for
determining what to truncate. Replaying the WAL would remove all
segments older than 'endTruncMemb', regardless of
'startTruncMemb'. The 'startTruncOff' stored in the WAL record was
similarly unnecessary even before 64-bit multixid offsets, it was
stored just for the sake of symmetry with 'startTruncMemb'. Remove
both from the WAL record, and rename the remaining 'endTruncOff' to
'oldestMulti' and 'endTruncMemb' to 'oldestOffset', for consistency
with the variable names used for them in other places.

Reviewed-by: Andrey Borodin <x4mmm@yandex-team.ru>
Discussion: https://www.postgresql.org/message-id/000301b2-5b81-4938-bdac-90f6eb660843@iki.fi
This commit is contained in:
Heikki Linnakangas
2026-01-15 13:34:50 +02:00
parent da265a8717
commit c4b71e6f60
4 changed files with 34 additions and 128 deletions
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10
src/include/access/multixact.h
View File

@@ -83,13 +83,11 @@ typedef struct xl_multixact_truncate
{
Oid oldestMultiDB;
/* to-be-truncated range of multixact offsets */
MultiXactId startTruncOff; /* just for completeness' sake */
MultiXactId endTruncOff;
/* truncate multixact offsets older than this */
MultiXactId oldestMulti;
/* to-be-truncated range of multixact members */
MultiXactOffset startTruncMemb;
MultiXactOffset endTruncMemb;
/* truncate multixact members older than this */
MultiXactOffset oldestOffset;
} xl_multixact_truncate;
#define SizeOfMultiXactTruncate (sizeof(xl_multixact_truncate))

2
src/include/access/xlog_internal.h
View File

@@ -31,7 +31,7 @@
/*
* Each page of XLOG file has a header like this:
*/
#define XLOG_PAGE_MAGIC 0xD11A /* can be used as WAL version indicator */
#define XLOG_PAGE_MAGIC 0xD11B /* can be used as WAL version indicator */
typedef struct XLogPageHeaderData
{