From: | Artur Zakirov <a(dot)zakirov(at)postgrespro(dot)ru> |
---|---|
To: | Andres Freund <andres(at)anarazel(dot)de>, Petr Jelinek <petr(at)2ndquadrant(dot)com> |
Cc: | Simon Riggs <simon(at)2ndQuadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Craig Ringer <craig(at)2ndquadrant(dot)com> |
Subject: | Re: Proposal: Generic WAL logical messages |
Date: | 2016-02-27 16:35:12 |
Message-ID: | 56D1D040.2030408@postgrespro.ru |
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Thread: | |
Lists: | pgsql-hackers |
Hello,
On 27.02.2016 03:05, Andres Freund wrote:
> Hi,
>
> I'm not really convinced by RegisterStandbyMsgPrefix() et al. There's
> not much documentation about what it actually is supposed to
> acomplish. Afaics you're basically forced to use
> shared_preload_libraries with it right now? Also, iterating through a
> linked list everytime something is logged doesn't seem very satisfying?
>
I have did some tests with a simple plugin. I have used event triggers
to send messages. It works, but I agree with Andres. We have problems if
plugin is not loaded. For example, if you will execute the query:
SELECT 'msg2' FROM pg_logical_send_message(false, 'test', 'msg2');
you will get the error (if plugin which should register a prefix is not
loaded yet):
ERROR: standby message prefix "test" is not registered
Some stylistic note (logical.c):
> +static void message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
> + XLogRecPtr message_lsn,
> + bool transactional, const char *prefix,
> + Size sz, const char *message)
> +{
> + LogicalDecodingContext *ctx = cache->private_data;
> + LogicalErrorCallbackState state;
> + ErrorContextCallback errcallback;
It should be written in the following way:
static void
message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
XLogRecPtr message_lsn,
bool transactional, const char *prefix,
Size sz, const char *message)
{
LogicalDecodingContext *ctx = cache->private_data;
LogicalErrorCallbackState state;
ErrorContextCallback errcallback;
--
Artur Zakirov
Postgres Professional: http://www.postgrespro.com
Russian Postgres Company
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