Improve eqjoinsel's ndistinct clamping to work for multiple levels of join.
This patch fixes an oversight in my commit 7f3eba30c9d622d1981b1368f2d79ba0999cdff2 of 2008-10-23. That patch accounted for baserel restriction clauses that reduced the number of rows coming out of a table (and hence the number of possibly-distinct values of a join variable), but not for join restriction clauses that might have been applied at a lower level of join. To account for the latter, look up the sizes of the min_lefthand and min_righthand inputs of the current join, and clamp with those in the same way as for the base relations. Noted while investigating a complaint from Ben Chobot, although this in itself doesn't seem to explain his report. Back-patch to 8.4; previous versions used different estimation methods for which this heuristic isn't relevant. Branch ------ REL9_1_STABLE Details ------- http://git.postgresql.org/pg/commitdiff/ca4f70ca779013599ec4c31c54944c2c7a584e92 Modified Files -------------- src/backend/utils/adt/selfuncs.c | 81 ++++++++++++++++++++++++++++++++++---- 1 files changed, 73 insertions(+), 8 deletions(-) -- Sent via pgsql-committers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-committers
