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Add pg_dissect_walfile_name() 

This function takes in input a WAL segment name and returns a tuple made
of the segment sequence number (dependent on the WAL segment size of the
cluster) and its timeline, as of a thin SQL wrapper around the existing
XLogFromFileName().

This function has multiple usages, like being able to compile a LSN from
a file name and an offset, or finding the timeline of a segment without
having to do to some maths based on the first eight characters of the
segment.

Bump catalog version.

Author: Bharath Rupireddy
Reviewed-by: Nathan Bossart, Kyotaro Horiguchi, Maxim Orlov, Michael
Paquier
Discussion: https://postgr.es/m/CALj2ACWV=FCddsxcGbVOA=cvPyMr75YCFbSQT6g4KDj=gcJK4g@mail.gmail.com
This commit is contained in:
Michael Paquier 2022-12-20 13:36:27 +09:00
parent b3bb7d12af
commit cca1863489
6 changed files with 125 additions and 1 deletions
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33
doc/src/sgml/func.sgml
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@ -26098,6 +26098,22 @@ LOG: Grand total: 1651920 bytes in 201 blocks; 622360 free (88 chunks); 1029560
</para></entry>
</row>
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
<primary>pg_dissect_walfile_name</primary>
</indexterm>
<function>pg_dissect_walfile_name</function> ( <parameter>file_name</parameter> <type>text</type> )
<returnvalue>record</returnvalue>
( <parameter>segno</parameter> <type>numeric</type>,
<parameter>timeline_id</parameter> <type>bigint</type> )
</para>
<para>
Extracts the file sequence number and timeline ID from a WAL file
name.
</para></entry>
</row>
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
@ -26155,6 +26171,23 @@ postgres=# SELECT * FROM pg_walfile_name_offset((pg_backup_stop()).lsn);
needs to be archived.
</para>
<para>
<function>pg_dissect_walfile_name</function> is useful to compute a
<acronym>LSN</acronym> from a file offset and WAL file name, for example:
<programlisting>
postgres=# \set file_name '000000010000000100C000AB'
postgres=# \set offset 256
postgres=# SELECT '0/0'::pg_lsn + pd.segno * ps.setting::int + :offset AS lsn
FROM pg_dissect_walfile_name(:'file_name') pd,
pg_show_all_settings() ps
WHERE ps.name = 'wal_segment_size';
lsn
---------------
C001/AB000100
(1 row)
</programlisting>
</para>
</sect2>
<sect2 id="functions-recovery-control">

53
src/backend/access/transam/xlogfuncs.c
View File

@ -432,6 +432,59 @@ pg_walfile_name(PG_FUNCTION_ARGS)
PG_RETURN_TEXT_P(cstring_to_text(xlogfilename));
}
/*
* Extract the sequence number and the timeline ID from given a WAL file
* name.
*/
Datum
pg_dissect_walfile_name(PG_FUNCTION_ARGS)
{
#define PG_DISSECT_WALFILE_NAME_COLS 2
char *fname = text_to_cstring(PG_GETARG_TEXT_PP(0));
char *fname_upper;
char *p;
TimeLineID tli;
XLogSegNo segno;
Datum values[PG_DISSECT_WALFILE_NAME_COLS] = {0};
bool isnull[PG_DISSECT_WALFILE_NAME_COLS] = {0};
TupleDesc tupdesc;
HeapTuple tuple;
char buf[256];
Datum result;
fname_upper = pstrdup(fname);
/* Capitalize WAL file name. */
for (p = fname_upper; *p; p++)
*p = pg_toupper((unsigned char) *p);
if (!IsXLogFileName(fname_upper))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("invalid WAL file name \"%s\"", fname)));
XLogFromFileName(fname_upper, &tli, &segno, wal_segment_size);
if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
elog(ERROR, "return type must be a row type");
/* Convert to numeric. */
snprintf(buf, sizeof buf, UINT64_FORMAT, segno);
values[0] = DirectFunctionCall3(numeric_in,
CStringGetDatum(buf),
ObjectIdGetDatum(0),
Int32GetDatum(-1));
values[1] = Int64GetDatum(tli);
tuple = heap_form_tuple(tupdesc, values, isnull);
result = HeapTupleGetDatum(tuple);
PG_RETURN_DATUM(result);
#undef PG_DISSECT_WALFILE_NAME_COLS
}
/*
* pg_wal_replay_pause - Request to pause recovery
*

2
src/include/catalog/catversion.h
View File

@ -57,6 +57,6 @@
*/
/* yyyymmddN */
#define CATALOG_VERSION_NO 202212191
#define CATALOG_VERSION_NO 202212201
#endif

7
src/include/catalog/pg_proc.dat
View File

@ -6372,6 +6372,13 @@
{ oid => '2851', descr => 'wal filename, given a wal location',
proname => 'pg_walfile_name', prorettype => 'text', proargtypes => 'pg_lsn',
prosrc => 'pg_walfile_name' },
{ oid => '8205',
descr => 'sequence number and timeline ID given a wal filename',
proname => 'pg_dissect_walfile_name', provolatile => 's',
prorettype => 'record', proargtypes => 'text',
proallargtypes => '{text,numeric,int8}', proargmodes => '{i,o,o}',
proargnames => '{file_name,segno,timeline_id}',
prosrc => 'pg_dissect_walfile_name' },
{ oid => '3165', descr => 'difference in bytes, given two wal locations',
proname => 'pg_wal_lsn_diff', prorettype => 'numeric',

23
src/test/regress/expected/misc_functions.out
View File

@ -619,3 +619,26 @@ SELECT count(*) > 0 AS ok FROM pg_control_system();
t
(1 row)
-- pg_dissect_walfile_name
SELECT * FROM pg_dissect_walfile_name(NULL);
segno | timeline_id
-------+-------------
|
(1 row)
SELECT * FROM pg_dissect_walfile_name('invalid');
ERROR: invalid WAL file name "invalid"
SELECT segno > 0 AS ok_segno, timeline_id
FROM pg_dissect_walfile_name('000000010000000100000000');
ok_segno | timeline_id
----------+-------------
t | 1
(1 row)
SELECT segno > 0 AS ok_segno, timeline_id
FROM pg_dissect_walfile_name('ffffffFF00000001000000af');
ok_segno | timeline_id
----------+-------------
t | 4294967295
(1 row)

8
src/test/regress/sql/misc_functions.sql
View File

@ -229,3 +229,11 @@ SELECT count(*) > 0 AS ok FROM pg_control_checkpoint();
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_dissect_walfile_name
SELECT * FROM pg_dissect_walfile_name(NULL);
SELECT * FROM pg_dissect_walfile_name('invalid');
SELECT segno > 0 AS ok_segno, timeline_id
FROM pg_dissect_walfile_name('000000010000000100000000');
SELECT segno > 0 AS ok_segno, timeline_id
FROM pg_dissect_walfile_name('ffffffFF00000001000000af');