On 11/15/2011 05:46 AM, MirrorX wrote:
i am facing an issue concerning cancelled queries made on a hot standby server. if we suppose that there are some tables that are never changed (no inserts/updates/deletes) and that autovacuum is set to false for these tables, what else could there be affecting these tables and consequently cancelling my queries? thx in advance for any suggestions
Query cancellation isn't targeted this way. Whether or not a query needs to be canceled by vacuum cleanup depends on whether any open transaction can see the rows that are being cleaned up. I think you have the understandable belief what rows are actually being viewed by the query running on the standby matter; they don't.
Let's say you have a long-running query Q accessing a table A on the standby. Then some vacuum cleanup of table B happens on the master. Q can then be canceled when those cleanup records are replicated. The fact that A is never changed and doesn't have autovacuum enabled doesn't matter. Because it's possible for Q to see B, it's canceled regardless of whether it's looked at it yet.
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