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(SIGUSR1, which we have not been using recently) instead of piggybacking on SIGUSR2-driven NOTIFY processing. This has several good results: the processing needed to drain the sinval queue is a lot less than the processing needed to answer a NOTIFY; there's less contention since we don't have a bunch of backends all trying to acquire exclusive lock on pg_listener; backends that are sitting inside a transaction block can still drain the queue, whereas NOTIFY processing can't run if there's an open transaction block. (This last is a fairly serious issue that I don't think we ever recognized before --- with clients like JDBC that tend to sit with open transaction blocks, the sinval queue draining mechanism never really worked as intended, probably resulting in a lot of useless cache-reset overhead.) This is the last of several proposed changes in response to Philip Warner's recent report of sinval-induced performance problems.
39 lines
1.2 KiB
C
39 lines
1.2 KiB
C
/*-------------------------------------------------------------------------
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*
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* async.h
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* Asynchronous notification: NOTIFY, LISTEN, UNLISTEN
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*
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* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/commands/async.h,v 1.24 2004/05/23 03:50:45 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef ASYNC_H
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#define ASYNC_H
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extern bool Trace_notify;
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/* notify-related SQL statements */
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extern void Async_Notify(char *relname);
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extern void Async_Listen(char *relname, int pid);
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extern void Async_Unlisten(char *relname, int pid);
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/* perform (or cancel) outbound notify processing at transaction commit */
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extern void AtCommit_Notify(void);
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extern void AtAbort_Notify(void);
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/* signal handler for inbound notifies (SIGUSR2) */
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extern void NotifyInterruptHandler(SIGNAL_ARGS);
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/*
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* enable/disable processing of inbound notifies directly from signal handler.
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* The enable routine first performs processing of any inbound notifies that
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* have occurred since the last disable.
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*/
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extern void EnableNotifyInterrupt(void);
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extern bool DisableNotifyInterrupt(void);
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#endif /* ASYNC_H */
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