Re: [BUGS] BUG #14469: Wrong cost estimates for merge append plan with partitions.

Alexey Ermakov <alexey.ermakov@postgresql-consulting.com> writes:
> I think we should change that estimation and in case when child node 
> expected to return only one row (and really 0 rows) we should use it's 
> total_cost as base for estimation of startup_cost.

This would make sense as part of the overall rethinking of startup_cost
discussed in
https://www.postgresql.org/message-id/flat/31065.1481742760%40sss.pgh.pa.us
but I'm disinclined to do it in isolation.  Redefining startup_cost for
just one path type seems likely to create more problems than it solves.

            regards, tom lane


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