Re: pgsql: Generic Messages for Logical Decoding

On April 6, 2016 5:00:54 PM GMT+02:00, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
>On Wed, Apr 6, 2016 at 6:08 PM, Simon Riggs <simon(at)2ndquadrant(dot)com>
>wrote:
>> Generic Messages for Logical Decoding
>>
>> API and mechanism to allow generic messages to be inserted into WAL
>that are
>> intended to be read by logical decoding plugins. This commit adds an
>optional
>> new callback to the logical decoding API.
>
>When I specify very long text message, pg_xlogdump failed to dump
>correctly the WAL file which should contain that inserted text message.
>Isn't this a bug?
>
>You can reproduce the problem by the following steps.
>
>=# SELECT pg_xlogfile_name(pg_switch_xlog());
> pg_xlogfile_name
>--------------------------
> 000000010000000000000003
>(1 row)
>
>=# SELECT pg_xlogfile_name(pg_current_xlog_location());
> pg_xlogfile_name
>--------------------------
> 000000010000000000000003
>(1 row)
>
>=# SELECT pg_logical_emit_message(true, 'test',
>repeat('0123456789ABCDEFG', 1024*1024));
> pg_logical_emit_message
>-------------------------
> 0/510CD40
>(1 row)
>
>=# SELECT pg_xlogfile_name(pg_current_xlog_location());
> pg_xlogfile_name
>--------------------------
> 000000010000000000000005
>(1 row)
>
>=# insert into t values(0,0);
>INSERT 0 1
>postgres=# SELECT pg_xlogfile_name(pg_current_xlog_location());
> pg_xlogfile_name
>--------------------------
> 000000010000000000000005
>(1 row)
>
>The WAL record of pg_logical_emit_message() should be stored in
>000000010000000000000004 and 000000010000000000000005.
>The WAL record of last insertion should be stored in
>000000010000000000000005.
>But the results of pg_xlogdump were wrong as follows.
>
>$ pg_xlogdump data/pg_xlog/000000010000000000000004
>rmgr: Standby len (rec/tot): 24/ 50, tx: 0, lsn:
>0/04000028, prev 0/030146F8, desc: RUNNING_XACTS nextXid 863
>latestCompletedXid 862 oldestRunningXid 863
>
>$ pg_xlogdump data/pg_xlog/000000010000000000000005
>pg_xlogdump: FATAL: could not find a valid record after 0/5000000

If you specify a file it only looks at records in that file. Try with -s.
--
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