| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | pgsql-hackers(at)postgreSQL(dot)org |
| Cc: | Neil Conway <neilc(at)samurai(dot)com>, "atsorgassa" <Kontakt(at)atsorgassa(dot)de> |
| Subject: | TupleDesc refcounting, again |
| Date: | 2006-05-19 02:32:53 |
| Message-ID: | 23860.1148005973@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Those of you with long memories may recall a discussion back in January
about reference-counting TupleDescs retrieved by lookup_rowtype_tupdesc().
I didn't like the patch Neil Conway developed for this, so I'm on the
hook to find a better answer before 8.2 comes out. I haven't forgotten
... but I was reminded of it while looking at the performance issue
pointed out by Marc Orgassa here:
http://archives.postgresql.org/pgsql-novice/2006-05/msg00153.php
If oprofile is to be trusted, Marc's second example spends something
close to forty percent of its runtime in CreateTupleDescCopy()
operations (including the subsidiary memcpy() calls). Yikes.
A reference-counting mechanism would have to be cheaper than that.
So I'll try to bubble this issue up to the top of the to-do queue
again...
regards, tom lane
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