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How to know a table has been modified?

From: Tatsuo Ishii <ishii(at)postgresql(dot)org>
To: pgsql-hackers(at)postgresql(dot)org
Subject: How to know a table has been modified?
Date: 2012-02-26 05:11:15
Message-ID: 20120226.141115.509677969352231723.t-ishii@sraoss.co.jp (view raw or flat)
Thread:
Lists: pgsql-hackers
I'm working on implementing query cache in pgpool-II. I want to know
if a table has been modified because pgpool-II has to invalidate cache
if corresponding table is modified. For DDL/DML it would be doable
since pgpool-II knows all SQLs sent from clients. Problem is, implicit
table modifications done by CASCADE, TRIGGERS and so on.

create table t1(i int, j int);
create table t2(i int references t1.i);
drop table t1 cascade;

In this example, if t1 is dropped, t2 is dropped as well. So query
cache corresponding to t1 and t2 should be invalidated. The only way I
could thinking of is, looking into pg_depend. I would like to know if
there's any better/convenient way to know it.

For TRIGGER, I cannot thinking of any way. Any idea will be welcome.
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese: http://www.sraoss.co.jp

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