| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Luca Ferrari <fluca1978(at)infinito(dot)it> |
| Cc: | pgsql-general <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: explain doubt |
| Date: | 2012-06-25 14:09:14 |
| Message-ID: | 20619.1340633354@sss.pgh.pa.us |
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| Lists: | pgsql-general |
Luca Ferrari <fluca1978(at)infinito(dot)it> writes:
> Now, what is the .35 in the cost of the bitmap index scan nodes?
If you're going to get picky about second-order cost components,
it's time to start reading the source code:
http://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/backend/optimizer/path/costsize.c;h=480c1b7425ce66a02e2e10711359143ea7ffe59c;hb=HEAD#l218
http://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/backend/utils/adt/selfuncs.c;h=95e46276f0a8911758f4ec02b993193bf55eee15;hb=HEAD#l6087
The short answer though is that this is probably coming from CPU cost
components not disk-access components.
regards, tom lane
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