On Tue, Dec 13, 2022 at 09:32:19PM +0530, Bharath Rupireddy wrote: > Okay, here's the v5 patch that I could come up with. It basically adds > functions for dissecting WAL file names and computing offset from lsn. > Thoughts?
I had a second look at that, and I still have mixed feelings about the addition of the SQL function, no real objection about pg_dissect_walfile_name(). I don't really think that we need a specific handling with a new macro from xlog_internal.h that does its own parsing of the segment number while XLogFromFileName() can do that based on the user input, so I have simplified that. A second thing is the TLI that had better be returned as int8 and not int4 so as we don't have a negative number for a TLI higher than 2B in a WAL segment name. -- Michael
From 25fb0848cf3220a5fc9638c2cfd116e5390be887 Mon Sep 17 00:00:00 2001
From: Michael Paquier <mich...@paquier.xyz>
Date: Mon, 19 Dec 2022 17:02:16 +0900
Subject: [PATCH v6] Add utility functions to disset WAL file name and compute
offset
---
src/include/catalog/pg_proc.dat | 7 +++
src/backend/access/transam/xlogfuncs.c | 53 ++++++++++++++++++++
src/test/regress/expected/misc_functions.out | 18 +++++++
src/test/regress/sql/misc_functions.sql | 8 +++
doc/src/sgml/func.sgml | 16 ++++++
5 files changed, 102 insertions(+)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 719599649a..79cfd1378d 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6365,6 +6365,13 @@
{ 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', prorettype => 'record',
+ proargtypes => 'text', proallargtypes => '{text,numeric,int8}',
+ provolatile => 's', 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',
diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c
index 487d5d9cac..0a31837ef1 100644
--- a/src/backend/access/transam/xlogfuncs.c
+++ b/src/backend/access/transam/xlogfuncs.c
@@ -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
*
diff --git a/src/test/regress/expected/misc_functions.out b/src/test/regress/expected/misc_functions.out
index 88bb696ded..fb676e9971 100644
--- a/src/test/regress/expected/misc_functions.out
+++ b/src/test/regress/expected/misc_functions.out
@@ -619,3 +619,21 @@ SELECT count(*) > 0 AS ok FROM pg_control_system();
t
(1 row)
+-- pg_dissect_walfile_name
+SELECT segno > 0 AS ok_segno, timeline_id
+ 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)
+
diff --git a/src/test/regress/sql/misc_functions.sql b/src/test/regress/sql/misc_functions.sql
index b07e9e8dbb..74cfc31913 100644
--- a/src/test/regress/sql/misc_functions.sql
+++ b/src/test/regress/sql/misc_functions.sql
@@ -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 segno > 0 AS ok_segno, timeline_id
+ 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');
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 1cd8b11334..2f05b06f14 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -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>
+ Extract 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>
--
2.39.0
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