From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Tony Cebzanov <tonyceb(at)andrew(dot)cmu(dot)edu> |
Cc: | Richard Huxton <dev(at)archonet(dot)com>, pgsql-sql(at)postgresql(dot)org |
Subject: | Re: Avoiding cycles in a directed graph |
Date: | 2010-03-16 21:09:12 |
Message-ID: | 14550.1268773752@sss.pgh.pa.us |
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Tony Cebzanov <tonyceb(at)andrew(dot)cmu(dot)edu> writes:
> I'm okay with running the big, fat WITH RECURSIVE query in my insert
> trigger if I have to -- it won't be great for performance, but I don't
> expect this to be a frequent operation, so I'll accept the performance
> hit if it works.
> Unfortunately I can't even get that working. Here's the (not at all
> functional) trigger I've got right now, which only detects the cycle
> *after* it's been inserted, which is of no help at all. Any way I can
> modify this to do the right thing?
Run it in an AFTER trigger?
If you don't expect this to be common, maybe you could fix the
concurrency issue by taking a table-wide lock that locks out
other writers.
regards, tom lane
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