| From: | Yang Zhang <yanghatespam(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Performance cost of a sort-merge join |
| Date: | 2010-02-22 17:51:19 |
| Message-ID: | 9066fa251002220951q7ccf8f3enc5261c665bbc6edd@mail.gmail.com |
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| Lists: | pgsql-general |
On Mon, Feb 22, 2010 at 12:10 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> I've left it running over night. By
>> comparison, a "select * from metarelcloud_transactionlog order by
>> transactionid" takes on the order of seconds/minutes (at least in
>> MySQL).
>
> That's got approximately nothing to do with this query.
Isn't that exactly what the leaf sorts are doing? By comparison,
"select * from metarelcloud_transactionlog order by transactionid"
takes much, much longer in PG (it's been running for 68 minutes now,
and still going, whereas MySQL took 6 minutes).
--
Yang Zhang
http://www.mit.edu/~y_z/
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