On 2010-10-26, John R Pierce <pierce@xxxxxxxxxxxx> wrote: > > count(*) has to read the whole table to get the accurate count. The > reason for this is that different clients can see different versions of > that table, for instance, if client A is already in a transaction, and > client B then does an INSERT, the two clients will see different values > for the count. They may or may not. the default transaction isolation level "read commited" allows a session to see most changes that were committed externally after the start of the transaction. Tlso the index may include deleted rows. which is another reason count(*) does a table scan. -- ÉÇpun uÊop ÉoÉÉ sÆuÄÊÇÇÉâ -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
