Re: select max(id) from aTable is very slow - Mailing list pgsql-performance

David Teran wrote:
> Hi,
>
> we have a table with about 6.000.000 rows. There is an index on a
> column with the name id which is an integer and serves as primary key.
>
> When we execute select max(id) from theTable; it takes about 10
> seconds. Explain analyze returns:

Due to the open-ended nature of PG's aggregate function system, it can't
see inside the max() function to realise it doesn't need all the values.

Fortune favours the flexible however - the simple workaround is to use
the equivalent:
   SELECT id FROM theTable ORDER BY id DESC LIMIT 1;

--
   Richard Huxton
   Archonet Ltd