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modify segno. for pg_walfile_name() and pg_walfile_name_offset()
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
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-13
lines changed

4 files changed

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lines changed

‎doc/src/sgml/func.sgml

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

‎src/backend/access/transam/xlogfuncs.c

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

Lines changed: 29 additions & 1 deletion
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@@ -619,7 +619,7 @@ SELECT count(*) > 0 AS ok FROM pg_control_system();
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t
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(1 row)
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-- pg_split_walfile_name
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-- pg_split_walfile_name, pg_walfile_name & pg_walfile_name_offset
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SELECT * FROM pg_split_walfile_name(NULL);
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segment_number | timeline_id
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----------------+-------------
@@ -642,3 +642,31 @@ SELECT segment_number > 0 AS ok_segment_number, timeline_id
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t | 4294967295
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(1 row)
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SELECT setting::int8 AS segment_size
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FROM pg_settings
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WHERE name = 'wal_segment_size'
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\gset
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SELECT segment_number, file_offset
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FROM pg_walfile_name_offset('0/0'::pg_lsn + :segment_size),
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pg_split_walfile_name(file_name);
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segment_number | file_offset
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----------------+-------------
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1 | 0
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(1 row)
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SELECT segment_number, file_offset
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FROM pg_walfile_name_offset('0/0'::pg_lsn + :segment_size + 1),
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pg_split_walfile_name(file_name);
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segment_number | file_offset
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----------------+-------------
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1 | 1
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(1 row)
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SELECT segment_number, file_offset = :segment_size - 1
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FROM pg_walfile_name_offset('0/0'::pg_lsn + :segment_size - 1),
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pg_split_walfile_name(file_name);
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segment_number | ?column?
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----------------+----------
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0 | t
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(1 row)
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‎src/test/regress/sql/misc_functions.sql

Lines changed: 14 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -230,10 +230,23 @@ SELECT count(*) > 0 AS ok FROM pg_control_init();
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SELECT count(*) > 0 AS ok FROM pg_control_recovery();
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SELECT count(*) > 0 AS ok FROM pg_control_system();
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-- pg_split_walfile_name
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-- pg_split_walfile_name, pg_walfile_name & pg_walfile_name_offset
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SELECT * FROM pg_split_walfile_name(NULL);
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SELECT * FROM pg_split_walfile_name('invalid');
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SELECT segment_number > 0 AS ok_segment_number, timeline_id
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FROM pg_split_walfile_name('000000010000000100000000');
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SELECT segment_number > 0 AS ok_segment_number, timeline_id
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FROM pg_split_walfile_name('ffffffFF00000001000000af');
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SELECT setting::int8 AS segment_size
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FROM pg_settings
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WHERE name = 'wal_segment_size'
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\gset
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SELECT segment_number, file_offset
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FROM pg_walfile_name_offset('0/0'::pg_lsn + :segment_size),
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pg_split_walfile_name(file_name);
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SELECT segment_number, file_offset
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FROM pg_walfile_name_offset('0/0'::pg_lsn + :segment_size + 1),
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pg_split_walfile_name(file_name);
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SELECT segment_number, file_offset = :segment_size - 1
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FROM pg_walfile_name_offset('0/0'::pg_lsn + :segment_size - 1),
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pg_split_walfile_name(file_name);

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