On Mon, Nov 13, 2023 at 09:49:53AM -0800, Andres Freund wrote:
> Hi,
>
> On 2023-11-13 12:14:57 -0500, Bruce Momjian wrote:
> > +SELECT *
> > +FROM (values ('0/16ffffff'), ('0/17000000'), ('0/17000001')) as t(lsn),
> > + LATERAL pg_walfile_name_offset(lsn::pg_lsn),
> > + LATERAL pg_walfile_name(lsn::pg_lsn);
> > + lsn | file_name | file_offset | pg_walfile_name
> >
> > +------------+--------------------------+-------------+--------------------------
> > + 0/16ffffff | 000000010000000000000016 | 16777215 |
> > 000000010000000000000016
> > + 0/17000000 | 000000010000000000000017 | 0 |
> > 000000010000000000000017
> > + 0/17000001 | 000000010000000000000017 | 1 |
> > 000000010000000000000017
> > +(3 rows)
>
> These would break when testing with a different segment size. Today that's not
> the case...
Okay, test removed in the updated patch.
--
Bruce Momjian <br...@momjian.us> https://momjian.us
EDB https://enterprisedb.com
Only you can decide what is important to you.
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index d963f0a0a0..7c22420839 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -27044,11 +27044,6 @@ 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>
diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c
index 45a70668b1..45452d937c 100644
--- a/src/backend/access/transam/xlogfuncs.c
+++ b/src/backend/access/transam/xlogfuncs.c
@@ -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);
diff --git a/src/test/regress/expected/misc_functions.out b/src/test/regress/expected/misc_functions.out
index c669948370..9302134077 100644
--- a/src/test/regress/expected/misc_functions.out
+++ b/src/test/regress/expected/misc_functions.out
@@ -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)
+
diff --git a/src/test/regress/sql/misc_functions.sql b/src/test/regress/sql/misc_functions.sql
index b57f01f3e9..d3dc591173 100644
--- a/src/test/regress/sql/misc_functions.sql
+++ b/src/test/regress/sql/misc_functions.sql
@@ -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);
