| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Peter Eisentraut <peter_e(at)gmx(dot)net> |
| Cc: | Itagaki Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Trigger with WHEN clause (WIP) |
| Date: | 2009-10-16 12:02:22 |
| Message-ID: | 1255694542.30088.3388.camel@ebony |
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| Lists: | pgsql-hackers |
On Fri, 2009-10-16 at 14:39 +0300, Peter Eisentraut wrote:
> On Fri, 2009-10-16 at 09:31 +0100, Simon Riggs wrote:
> > * It will reduce size of in-memory pending trigger list (for large
> > statements)
>
> But this won't be the outcome when it's implemented the way it is being
> proposed, which checks the where clause just before executing the
> trigger function.
Thanks for pointing that out.
I'm giving reasons why we'd want a WHEN clause. If the current
implementation doesn't do all that it could, then ISTM thats a reason to
reject patch for now, but not for all time.
Incidentally, re-accessing a data block at end of statement may have
caused to block to fall out of cache and then be re-accessed again. So
optimising that away can save on I/O as well.
--
Simon Riggs www.2ndQuadrant.com
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