Re: Indexing a Boolean or Null column?

"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