On 10/11/2010 3:54 PM, Neil Whelchel wrote:
1. A faster count(*), or something like my proposed estimate(*). 2. A way to get the total rows matched when using LIMIT and OFFSET before LIMIT and OFFSET are applied.
The biggest single problem with "select count(*)" is that it is seriously overused. People use that idiom to establish existence, which usually leads to a performance disaster in the application using it, unless the table has no more than few hundred records. SQL language, of which PostgreSQL offers an excellent implementation, offers [NOT] EXISTS clause since its inception in the Jurassic era. The problem is with the sequential scan, not with counting. I'd even go as far as to suggest that 99% instances of the "select count(*)" idiom are probably bad use of the SQL language.
-- Mladen Gogala Sr. Oracle DBA 1500 Broadway New York, NY 10036 (212) 329-5251 www.vmsinfo.com -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
