Hi,
Some time ago [1], I proposed print a message every time there isn't
autovacuum slots available and it asks for another one. It is not a complete
solution for autovacuum tuning but it would at least give us a hint that
number of workers is insufficient to keep up with the current load. The
accurate number of slots needed would be the optimal solution but that
information is not free (it would have to check every table in the databases
available to get the approximate number of slots needed. Approximate because
some table could be finishing the operation). A new warning is better than
nothing. If we decided to improve this area in a future we should remove the
warning but right now it would be an excelent hint to tune autovacuum.
[1] http://archives.postgresql.org/pgsql-hackers/2011-06/msg00678.php
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Euler Taveira de Oliveira - Timbira http://www.timbira.com.br/
PostgreSQL: Consultoria, Desenvolvimento, Suporte 24x7 e Treinamento