From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | "D(dot) Dante Lorenso" <dante(at)lorenso(dot)com> |
Cc: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Indexing a Boolean or Null column? |
Date: | 2004-01-04 04:26:52 |
Message-ID: | 17336.1073190412@sss.pgh.pa.us |
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Lists: | pgsql-performance |
"D. Dante Lorenso" <dante(at)lorenso(dot)com> writes:
> Does it make sense to have an index on data_is_active?
Hard to say. You weren't very clear about what fraction of the table
rows you expect to have data_is_active = true. If that's a very small
fraction, then an index might be worthwhile.
However, I'd suggest using a partial index that merges the is_active
test with some other useful behavior. For example, if this is a
common pattern:
> SELECT *
> FROM table
> WHERE data_lookup_key = 'pear'
> AND data_is_active IS TRUE;
then what you really want is
CREATE INDEX myindex ON table (data_lookup_key) WHERE data_is_active IS TRUE;
> I bet this is in a FAQ somewhere. Can you point me in the right
> direction?
See the docs on partial indexes.
regards, tom lane
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