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modify segno. for pg_walfile_name() and pg_walfile_name_offset()

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Previously these functions returned the previous segment number if the
LSN was on a segment boundary.  We now always return the current segment
number for an LSN.

Docs updated to reflect this change.  Regression tests added, author
Andres Freund.

Also mentioned in thread https://postgr.es/m/flat/20220204225057.GA1535307%40nathanxps13#d964275c9540d8395e138efc0a75f7e8

BACKWARD INCOMPATIBILITY

Reported-by: Kyotaro Horiguchi

Discussion: https://postgr.es/m/20190726.172120.101752680.horikyota.ntt@gmail.com

Co-authored-by: Kyotaro Horiguchi

Backpatch-through: master
This commit is contained in:
Bruce Momjian 2023-11-24 19:44:09 -05:00
parent 5c4c7efadd
commit 344afc7769
4 changed files with 45 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
doc/src/sgml/func.sgml
View File

@ -27075,11 +27075,6 @@ postgres=# SELECT * FROM pg_walfile_name_offset((pg_backup_stop()).lsn);
(1 row)
</programlisting>
Similarly, <function>pg_walfile_name</function> extracts just the write-ahead log file name.
When the given write-ahead log location is exactly at a write-ahead log file boundary, both
these functions return the name of the preceding write-ahead log file.
This is usually the desired behavior for managing write-ahead log archiving
behavior, since the preceding file is the last one that currently
needs to be archived.
</para>
<para>

8
src/backend/access/transam/xlogfuncs.c
View File

@ -374,10 +374,6 @@ pg_last_wal_replay_lsn(PG_FUNCTION_ARGS)
/*
* Compute an xlog file name and decimal byte offset given a WAL location,
* such as is returned by pg_backup_stop() or pg_switch_wal().
*
* Note that a location exactly at a segment boundary is taken to be in
* the previous segment. This is usually the right thing, since the
* expected usage is to determine which xlog file(s) are ready to archive.
*/
Datum
pg_walfile_name_offset(PG_FUNCTION_ARGS)
@ -414,7 +410,7 @@ pg_walfile_name_offset(PG_FUNCTION_ARGS)
/*
* xlogfilename
*/
XLByteToPrevSeg(locationpoint, xlogsegno, wal_segment_size);
XLByteToSeg(locationpoint, xlogsegno, wal_segment_size);
XLogFileName(xlogfilename, GetWALInsertionTimeLine(), xlogsegno,
wal_segment_size);
@ -457,7 +453,7 @@ pg_walfile_name(PG_FUNCTION_ARGS)
errhint("%s cannot be executed during recovery.",
"pg_walfile_name()")));
XLByteToPrevSeg(locationpoint, xlogsegno, wal_segment_size);
XLByteToSeg(locationpoint, xlogsegno, wal_segment_size);
XLogFileName(xlogfilename, GetWALInsertionTimeLine(), xlogsegno,
wal_segment_size);

30
src/test/regress/expected/misc_functions.out
View File

@ -619,7 +619,7 @@ SELECT count(*) > 0 AS ok FROM pg_control_system();
t
(1 row)
-- pg_split_walfile_name
-- pg_split_walfile_name, pg_walfile_name & pg_walfile_name_offset
SELECT * FROM pg_split_walfile_name(NULL);
segment_number | timeline_id
----------------+-------------
@ -642,3 +642,31 @@ SELECT segment_number > 0 AS ok_segment_number, timeline_id
t | 4294967295
(1 row)
SELECT setting::int8 AS segment_size
FROM pg_settings
WHERE name = 'wal_segment_size'
\gset
SELECT segment_number, file_offset
FROM pg_walfile_name_offset('0/0'::pg_lsn + :segment_size),
pg_split_walfile_name(file_name);
segment_number | file_offset
----------------+-------------
1 | 0
(1 row)
SELECT segment_number, file_offset
FROM pg_walfile_name_offset('0/0'::pg_lsn + :segment_size + 1),
pg_split_walfile_name(file_name);
segment_number | file_offset
----------------+-------------
1 | 1
(1 row)
SELECT segment_number, file_offset = :segment_size - 1
FROM pg_walfile_name_offset('0/0'::pg_lsn + :segment_size - 1),
pg_split_walfile_name(file_name);
segment_number | ?column?
----------------+----------
0 | t
(1 row)

15
src/test/regress/sql/misc_functions.sql
View File

@ -230,10 +230,23 @@ SELECT count(*) > 0 AS ok FROM pg_control_init();
SELECT count(*) > 0 AS ok FROM pg_control_recovery();
SELECT count(*) > 0 AS ok FROM pg_control_system();
-- pg_split_walfile_name
-- pg_split_walfile_name, pg_walfile_name & pg_walfile_name_offset
SELECT * FROM pg_split_walfile_name(NULL);
SELECT * FROM pg_split_walfile_name('invalid');
SELECT segment_number > 0 AS ok_segment_number, timeline_id
FROM pg_split_walfile_name('000000010000000100000000');
SELECT segment_number > 0 AS ok_segment_number, timeline_id
FROM pg_split_walfile_name('ffffffFF00000001000000af');
SELECT setting::int8 AS segment_size
FROM pg_settings
WHERE name = 'wal_segment_size'
\gset
SELECT segment_number, file_offset
FROM pg_walfile_name_offset('0/0'::pg_lsn + :segment_size),
pg_split_walfile_name(file_name);
SELECT segment_number, file_offset
FROM pg_walfile_name_offset('0/0'::pg_lsn + :segment_size + 1),
pg_split_walfile_name(file_name);
SELECT segment_number, file_offset = :segment_size - 1
FROM pg_walfile_name_offset('0/0'::pg_lsn + :segment_size - 1),
pg_split_walfile_name(file_name);