On 22 December 2017 at 12:45, Robert Haas <robertmh...@gmail.com> wrote: > PREPARE q3 (int, int) AS SELECT * FROM unpartitioned_table WHERE > partkey BETWEEN $1 AND $2; > > ...that has to decide whether to use an index. And to do that it has > to estimate what fraction of the table will match the BETWEEN clause. > That may be an uninformed guess, but it guesses something. We > probably want to do something here that makes the guess for a > partitioned_table similar to the guess for an unpartitioned_table.
Are you considering some sort of clauselist_selectivity() estimate on the given parameters and comparing that to the same selectivities that were determined for the previous custom plans? -- David Rowley http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
