On 4 June 2016 at 14:10, Christophe Pettus <x...@thebuild.com> wrote:
> Something I've noticed frequently is that HashAggregate will, especially if
> the children are Append with one of the nodes a non-seqscan, estimate 200
> rows rather than a calculated vlaue. Where is that value coming from? The
> statistics target, a hardwired constant, or something else?
Most likely from DEFAULT_NUM_DISTINCT in selfuncs.h. This is the
fallback, when nothing else can be used.
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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