On 01.03.2018 22:48, Andres Freund wrote:
Hi, I still don't think, as commented upon by Tom and me upthread, that we want this feature in the current form. Your arguments about layering violations seem to be counteracted by the fact that ProjectionIsNotChanged() basically appears to do purely executor work inside inside heapam.c.
ProjectionIsNotChanged doesn't perform evaluation itslef, is calls FormIndexDatum. FormIndexDatum is also called in 13 other places in Postgres: analyze.c, constraint.c, index.c, tuplesort, execIndexing.c I still think that trying to store somewhere result odf index expression evaluation to be able to reuse in index update is not so good idea: it complicates code and add extra dependencies between different modules. And benefits of such optimization are not obvious: is index expression evaluation is so expensive, then recheck_on_update should be prohibited for such index at all. -- Konstantin Knizhnik Postgres Professional: http://www.postgrespro.com The Russian Postgres Company
