On Fri, 26 Jul 2019 18:22:25 +0200
Jehan-Guillaume de Rorthais <j...@dalibo.com> wrote:
> On Fri, 26 Jul 2019 10:02:58 +0200
> Jehan-Guillaume de Rorthais <j...@dalibo.com> wrote:
>
> > On Fri, 26 Jul 2019 16:49:53 +0900 (Tokyo Standard Time)
> > Kyotaro Horiguchi <horikyota....@gmail.com> wrote:
> [...]
> > > We have an LSN reporting function each for several objectives.
> > >
> > > pg_current_wal_lsn
> > > pg_current_wal_insert_lsn
> > > pg_current_wal_flush_lsn
> > > pg_last_wal_receive_lsn
> > > pg_last_wal_replay_lsn
> >
> > Yes. In fact, my current implementation might be split as:
> >
> > pg_current_wal_tl: returns TL on a production cluster
> > pg_last_wal_received_tl: returns last received TL on a standby
> >
> > If useful, I could add pg_last_wal_replayed_tl. I don't think *insert_tl and
> > *flush_tl would be useful as a cluster in production is not supposed to
> > change its timeline during its lifetime.
> >
> > > But, I'm not sure just adding further pg_last_*_timeline() to
> > > this list is a good thing..
> >
> > I think this is a much better idea than mixing different case (production
> > and standby) in the same function as I did. Moreover, it's much more
> > coherent with other existing functions.
>
> Please, find in attachment a new version of the patch. It now creates two new
> fonctions:
>
> pg_current_wal_tl()
> pg_last_wal_received_tl()
I just found I forgot to use PG_RETURN_INT32 in pg_last_wal_received_tl().
Please find the corrected patch in attachment:
0001-v3-Add-functions-to-get-timeline.patch
Also, TimeLineID is declared as a uint32. So why do we use
PG_RETURN_INT32/Int32GetDatum to return a timeline and not PG_RETURN_UINT32?
See eg. in pg_stat_get_wal_receiver().
Regards,
>From 031d60de3e4239c83554c89c0c382c6390545434 Mon Sep 17 00:00:00 2001
From: Jehan-Guillaume de Rorthais <j...@dalibo.com>
Date: Thu, 25 Jul 2019 19:36:40 +0200
Subject: [PATCH] Add functions to get timeline
pg_current_wal_tl() returns the current timeline of a cluster in production.
pg_last_wal_received_tl() returns the timeline of the last xlog record
flushed to disk.
---
src/backend/access/transam/xlog.c | 17 +++++++++++++++++
src/backend/access/transam/xlogfuncs.c | 20 ++++++++++++++++++++
src/backend/replication/walreceiver.c | 19 +++++++++++++++++++
src/include/access/xlog.h | 1 +
src/include/catalog/pg_proc.dat | 12 ++++++++++++
5 files changed, 69 insertions(+)
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index da3d250986..fd30c88534 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -12243,3 +12243,20 @@ XLogRequestWalReceiverReply(void)
{
doRequestWalReceiverReply = true;
}
+
+/*
+ * Returns current active timeline.
+ */
+TimeLineID
+GetCurrentTimeLine(void)
+{
+ TimeLineID localTimeLineID;
+
+ SpinLockAcquire(&XLogCtl->info_lck);
+
+ localTimeLineID = XLogCtl->ThisTimeLineID;
+
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ return localTimeLineID;
+}
diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c
index b35043bf71..ae877be351 100644
--- a/src/backend/access/transam/xlogfuncs.c
+++ b/src/backend/access/transam/xlogfuncs.c
@@ -776,3 +776,23 @@ pg_promote(PG_FUNCTION_ARGS)
(errmsg("server did not promote within %d seconds", wait_seconds)));
PG_RETURN_BOOL(false);
}
+
+/*
+ * Returns the current timeline on a production cluster
+ */
+Datum
+pg_current_wal_tl(PG_FUNCTION_ARGS)
+{
+ TimeLineID currentTL;
+
+ if (RecoveryInProgress())
+ ereport(ERROR,
+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("recovery is in progress"),
+ errhint("%s cannot be executed during recovery.",
+ "pg_current_wal_tl()")));
+
+ currentTL = GetCurrentTimeLine();
+
+ PG_RETURN_INT32(currentTL);
+}
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index 6abc780778..9bffd822ff 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -1454,3 +1454,22 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
/* Returns the record as Datum */
PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
}
+
+/*
+ * Returns the timeline of the last xlog record flushed to WAL
+ */
+Datum
+pg_last_wal_received_tl(PG_FUNCTION_ARGS)
+{
+ TimeLineID lastReceivedTL;
+ WalRcvData *walrcv = WalRcv;
+
+ SpinLockAcquire(&walrcv->mutex);
+ lastReceivedTL = walrcv->receivedTLI;
+ SpinLockRelease(&walrcv->mutex);
+
+ if (!lastReceivedTL)
+ PG_RETURN_NULL();
+
+ PG_RETURN_INT32(lastReceivedTL);
+}
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index d519252aad..f0502c0b41 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -313,6 +313,7 @@ extern XLogRecPtr GetInsertRecPtr(void);
extern XLogRecPtr GetFlushRecPtr(void);
extern XLogRecPtr GetLastImportantRecPtr(void);
extern void RemovePromoteSignalFiles(void);
+extern TimeLineID GetCurrentTimeLine(void);
extern bool CheckPromoteSignal(void);
extern void WakeupRecovery(void);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 0902dce5f1..d7ec6ea100 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6006,6 +6006,18 @@
{ oid => '2851', descr => 'wal filename, given a wal location',
proname => 'pg_walfile_name', prorettype => 'text', proargtypes => 'pg_lsn',
prosrc => 'pg_walfile_name' },
+{ oid => '3434',
+ descr => 'current timeline',
+ proname => 'pg_current_wal_tl', prorettype => 'int4',
+ proargtypes => '', proallargtypes => '{int4}',
+ proargmodes => '{o}', proargnames => '{timeline}',
+ prosrc => 'pg_current_wal_tl' },
+{ oid => '3435',
+ descr => 'current wal flush timeline',
+ proname => 'pg_last_wal_received_tl', prorettype => 'int4',
+ proargtypes => '', proallargtypes => '{int4}',
+ proargmodes => '{o}', proargnames => '{timeline}',
+ prosrc => 'pg_last_wal_received_tl' },
{ oid => '3165', descr => 'difference in bytes, given two wal locations',
proname => 'pg_wal_lsn_diff', prorettype => 'numeric',
--
2.20.1
