Make PlaceHolderInfo lookup O(1). Up to now we've just searched the placeholder_list when we want to find the PlaceHolderInfo with a given ID. While there's no evidence of that being a problem in the field, an upcoming patch will add find_placeholder_info() calls in build_joinrel_tlist(), which seems likely to make it more of an issue: a joinrel emitting lots of PlaceHolderVars would incur O(N^2) cost, and we might be building a lot of joinrels in complex queries. Hence, add an array that can be indexed directly by phid to make the lookups constant-time.
Discussion: https://postgr.es/m/[email protected] Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/6569ca43973b754e8213072c8ddcae9e7baf2aaa Modified Files -------------- src/backend/optimizer/plan/analyzejoins.c | 3 +++ src/backend/optimizer/plan/planmain.c | 2 ++ src/backend/optimizer/util/placeholder.c | 43 +++++++++++++++++++++++++++---- src/backend/optimizer/util/var.c | 11 ++------ src/include/nodes/pathnodes.h | 5 ++++ 5 files changed, 50 insertions(+), 14 deletions(-)
