From: | Andrew Merrill <andrew(at)compclass(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Thomas Lockhart <lockhart(at)alumni(dot)caltech(dot)edu>, "Jackson, DeJuan" <djackson(at)cpsgroup(dot)com>, pgsql-sql(at)hub(dot)org, PGSQL Hackers <pgsql-hackers(at)hub(dot)org> |
Subject: | Re: [SQL] indexing a datetime by date |
Date: | 1999-03-30 17:25:39 |
Message-ID: | 37010913.4298B216@compclass.com |
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Lists: | pgsql-hackers pgsql-sql |
Tom Lane wrote:
> In the meantime, a workaround is to call the function using its
> builtin name:
>
> play=> create table notes (when datetime);
> CREATE
> play=> create index when_ndx3 on notes (datetime_date(when) date_ops);
> CREATE
Thanks, that helps - I can now index a datetime field by date.But the index
doesn't appear to be used:
db=> create index ndx3 on notes (datetime_date(when) date_ops);
CREATE
db=> vacuum analyze notes;
VACUUM
db=> explain select when from notes where when::date = 'now'::date;
NOTICE: QUERY PLAN:
Seq Scan on notes (cost=4330.37 size=43839 width=8)
EXPLAIN
So it appears that the optimizer doesn't like this index. (This is with
version 6.4.2.)
The table has about 90,000 rows, of which between 10 and 100 might match a
given date, so an index would really help.
Am I missing something simple here? Thanks again for all your help.
Andrew Merrill
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