From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Andrew Lazarus <andrew(at)pillette(dot)com> |
Cc: | Mark Kirkwood <markir(at)paradise(dot)net(dot)nz>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: index structure for 114-dimension vector |
Date: | 2007-04-21 00:44:31 |
Message-ID: | 3357.1177116271@sss.pgh.pa.us |
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Lists: | pgsql-performance |
Andrew Lazarus <andrew(at)pillette(dot)com> writes:
> Because I know the 25 closest are going to be fairly close in each
> coordinate, I did try a multicolumn index on the last 6 columns and
> used a +/- 0.1 or 0.2 tolerance on each. (The 25 best are very probably inside
> that hypercube on the distribution of data in question.)
> This hypercube tended to have 10-20K records, and took at least 4
> seconds to retrieve. I was a little surprised by how long that took.
> So I'm wondering if my data representation is off the wall.
A multicolumn btree index isn't going to be helpful at all. Jeff's idea
of using six single-column indexes with the above query might work,
though.
regards, tom lane
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