From: | Stefan Keller <sfkeller(at)gmail(dot)com> |
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To: | twoflower <standa(dot)kurik(at)gmail(dot)com> |
Cc: | "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org> |
Subject: | Re: [PERFORM] Re: Query > 1000× slowdown after adding datetime comparison |
Date: | 2015-08-31 20:24:35 |
Message-ID: | CAFcOn2-u8QE-0vwkUuEQ7b1m9+YfH=vjLAaJrhAh=zU4n9Hu1w@mail.gmail.com |
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Lists: | pgsql-performance |
2015-08-31 21:46 GMT+02:00 twoflower <standa(dot)kurik(at)gmail(dot)com> wrote:
> I created a new boolean column and filled it for every row in DOCUMENT with
> *(doc.date_last_updated >= date(now() - '171:00:00'::interval))*, reanalyzed
> ...
... and you've put an index on that new boolean column (say "updated")?
CREATE INDEX index_name ON some_table (boolean_field);
or tried a conditional index like
CREATE INDEX index_name ON some_table (some_field) WHERE boolean_field;
-S.
2015-08-31 21:46 GMT+02:00 twoflower <standa(dot)kurik(at)gmail(dot)com>:
> David G Johnston wrote
>> What happens if you pre-compute the date condition and hard code it?
>
> I created a new boolean column and filled it for every row in DOCUMENT with
> *(doc.date_last_updated >= date(now() - '171:00:00'::interval))*, reanalyzed
> the table and modified the query to just compare this column to TRUE. I
> expected this to be very fast, considering that a (to me, anyway) similar
> query also containing a constant value comparison finishes immediately.
> However, the query is running now for 4 minutes already. That's really
> interesting.
>
>
>
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