| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Daniel Farina <daniel(at)heroku(dot)com>, Craig Ringer <ringerc(at)ringerc(dot)id(dot)au>, Harold A(dot) Giménez <harold(dot)gimenez(at)gmail(dot)com> |
| Subject: | Re: [PERFORM] DELETE vs TRUNCATE explanation |
| Date: | 2012-07-19 21:02:08 |
| Message-ID: | 13265.1342731728@sss.pgh.pa.us |
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| Lists: | pgsql-hackers pgsql-performance |
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> What if we change the hash table to have RelFileNode as the key and an
> array of MAX_FORKNUM bitmapsets as the value? Then when you get a
> "forget" request, you can just zap all the sets to empty.
Hm ... the only argument I can really make against that is that there'll
be no way to move such a table into shared memory; but there's probably
little hope of that anyway, given points made upthread. The bitmapset
manipulations are a bit tricky but solvable, and I agree there's
something to be said for not tying this stuff so closely to the
mechanism for relfilenode recycling.
regards, tom lane
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