* John D. Burger (john@xxxxxxxxx) wrote: > My understanding is that PG will use an index on the referring side of a > foreign key for FK checks. How can I tell whether it's doing that? It should, when it makes sense, yes. Having the actual schema definitions would help in debugging this, of course. > EXPLAIN ANALYZE just shows something like this: > > => explain analyze delete from segments where segmentid = 24305259; What does: explain analyze delete from tokenizedSegments where segmentId = 24305259; look like? If more than a few percent of the tokenizedSegments table has a segmentId of 24305259 then PG may rightly be scanning the whole table sequantially because going through it randomly with an index would be slower. There's a few options which can tune those parameters in the planner, of course, but you might consider doing a test 'set enable_seqscan = false;' first, if it's indeed doing one, to see what the difference really is. Thanks, Stephen
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