From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | t-ishii(at)sra(dot)co(dot)jp |
Cc: | "Hiroshi Inoue" <Inoue(at)tpf(dot)co(dot)jp>, "Bruce Momjian" <maillist(at)candle(dot)pha(dot)pa(dot)us>, pgsql-hackers(at)postgreSQL(dot)org |
Subject: | Re: [HACKERS] md.c is feeling much better now, thank you |
Date: | 1999-09-05 15:33:27 |
Message-ID: | 5805.936545607@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Tatsuo Ishii <t-ishii(at)sra(dot)co(dot)jp> writes:
> Ok. I will give another example that seems more serious.
> test=> aaa;
> ERROR: parser: parse error at or near "aaa"
> -- transaction is aborted and the table file t1 is unlinked.
> test=> select * from t1;
> -- but parser doesn't know t1 does not exist any more.
> -- it tries to open t1 using mdopen(). (see including backtrace)
> -- mdopen() tries to open t1 and fails. In this case mdopen()
> -- creates t1!
> NOTICE: (transaction aborted): queries ignored until END
> *ABORT STATE*
Hmm. It seems a more straightforward solution would be to alter
pg_parse_and_plan so that the parser isn't even called if we have
already failed the current transaction; that is, the "queries ignored"
test should occur sooner. I'm rather surprised to realize that
we do run the parser in this situation...
> I think the long range solution would be let parser obtain certain
> locks as Tom said.
That would not solve this particular problem, since the lock manager
wouldn't know any better than the parser that the table doesn't really
exist any more.
> Until that I propose following solution. It looks
> simple, safe and would be neccessary anyway (I don't know why that
> check had not been implemented). See included patches.
This looks like it might be a good change, but I'm not quite as sure
as you are that it won't have any bad effects. Have you tested it?
regards, tom lane
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