On 16/03/10 21:09, Tom Lane wrote:
Tony Cebzanov<tony...@andrew.cmu.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.
Surely SELECT FOR UPDATE on the parents would be sufficient? If there's
no overlap between (currently non-cyclic) graphs being altered then
there can't be any conflict.
--
Richard Huxton
Archonet Ltd
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