Re: Streaming replication status

On Thu, 2010-01-14 at 17:33 +0900, Fujii Masao wrote:

> I added two new functions;
>
> (1) pg_last_xlog_receive_location() reports the last WAL location received
> and synced by walreceiver. If streaming replication is still in progress
> this will increase monotonically. If streaming replication has completed
> then this value will remain static at the value of the last WAL record
> received and synced. When the server has been started without a streaming
> replication then the return value will be InvalidXLogRecPtr (0/0).
>
> (2) pg_last_xlog_replay_location() reports the last WAL location replayed
> during recovery. If recovery is still in progress this will increase
> monotonically. If recovery has completed then this value will remain
> static at the value of the last WAL record applied. When the server has
> been started normally without a recovery then the return value will be
> InvalidXLogRecPtr (0/0).

I just noticed that these functions have almost the same name as
functions I wrote for Hot Standby and Heikki removed from that patch.
The function code and docs are 99% identical.

I'm happy that the code was used and it is BSD, though it does seem
strange to have this credited to others in the release notes.

>From May 2 2009 the patch included

+ <entry>
+
<literal><function>pg_last_recovered_xlog_location</function>()</literal>
+ </entry>
+ <entry><type>text</type></entry>
+ <entry>Returns the transaction log location of the last WAL
record
+ in the current recovery. If recovery is still in progress this
+ will increase monotonically. If recovery is complete then this value
will
+ remain static at the value of the last transaction applied during
that
+ recovery. When the server has been started normally this will
return
+ InvalidXLogRecPtr (0/0).
+ (zero).
+ </entry>

with code

+ /*
+ * Returns xlog location of last recovered WAL record.
+ */
+ Datum
+ pg_last_recovered_xlog_location(PG_FUNCTION_ARGS)
+ {
+ char location[MAXFNAMELEN];
+
+ {
+ /* use volatile pointer to prevent code rearrangement */
+ volatile XLogCtlData *xlogctl = XLogCtl;
+
+ SpinLockAcquire(&xlogctl->info_lck);
+
+ LastRec = xlogctl->recoveryLastRecPtr;
+
+ SpinLockRelease(&xlogctl->info_lck);
+ }
+
+ snprintf(location, sizeof(location), "%X/%X",
+ LastRec.xlogid, LastRec.xrecoff);
+ PG_RETURN_TEXT_P(cstring_to_text(location));
+ }

--
Simon Riggs www.2ndQuadrant.com