From: | hamann(dot)w(at)t-online(dot)de |
---|---|
To: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: optimize query? |
Date: | 2013-01-30 13:32:37 |
Message-ID: | 510920F5.mailx43Y11TD0Y@amadeus3.local |
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Thread: | |
Lists: | pgsql-general |
Bob Futrelle wrote:
If looking for the variants with a single suffixed character is all you'll
ever need to do:
Do a single pass on the large table, after creating a field, 'trunc' that
contains a truncated version of the item, e.g., adding XY423 to trunc for
each entry of the form XY423A, or XY423B, etc. This would be a one-time
operation.
Hi Bob,
unfortunately it is not because the suffix pattern is not always the same.
On the other hand, I tried to split the query into
select substring (code from '^[A-Z]+[0-9]+') as code into tmp table t
select .... where tab2.code = t.code
which definitely was a big improvement. I believe that most of the time
passing in a pattern like that would work
So thank you for that tip
Regards
Wolfgang
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