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Re: [PERFORM] DELETE vs TRUNCATE explanation

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Jeff Janes <jeff.janes@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, Daniel Farina <daniel@heroku.com>, Craig Ringer <ringerc@ringerc.id.au>, Harold A. Giménez <harold.gimenez@gmail.com>
Date: 2012-07-19T21:02:08Z
Lists: pgsql-hackers, pgsql-performance 
Robert Haas <robertmhaas@gmail.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

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Scan the buffer pool just once, not once per fork, during relation drop.