I have a table with a field, "when", of type "datetime". I can't use
"date" because I need the times as well. I'm using PostgreSQL 6.4.2.
I'd like to identify all of the records with today's date, as in:
select when from notes where when::date = now()::date;
The query works, but is very slow. Explain confirms that a sequential
scan is being used.
I've tried indexing on when:
create index when_ndx1 on notes (when);
But that doesn't help, as (I suppose) the optimizer can't match
when::date with this index.
Neither of these works:
db=> create index when_ndx2 on notes (when::date);
ERROR: parser: parse error at or near "::"
db=> create index when_ndx3 on notes (date(when));
ERROR: DefineIndex: class not found
As a workaround, I've been using this:
select when from notes where when >= '3/29/1999 0:0:0' and when <=
'3/29/1999 23:59:59';
but that's ugly and requires hardcoding today's date each time, rather
than using now().
So, the question is, is there a way to index a datetime field by date?
Andrew Merrill
