Improve planner's handling of SetOp plans. Remove the code for inserting flag columns in the inputs of a SetOp. That was the only reason why there would be resjunk columns in a set-operations plan tree, so we can get rid of some code that supported that, too.
Get rid of choose_hashed_setop() in favor of building Paths for the hashed and sorted alternatives, and letting them fight it out within add_path(). Remove set_operation_ordered_results_useful(), which was giving wrong answers due to examining the wrong ancestor node: we need to examine the immediate SetOperationStmt parent not the topmost node. Instead make each caller of recurse_set_operations() pass down the relevant parent node. (This thinko seems to have led only to wasted planning cycles and possibly-inferior plans, not wrong query answers. Perhaps we should back-patch it, but I'm not doing so right now.) Teach generate_nonunion_paths() to consider pre-sorted inputs for sorted SetOps, rather than always generating a Sort node. Patch by me; thanks to Richard Guo and David Rowley for review. Discussion: https://postgr.es/m/1850138.1731549...@sss.pgh.pa.us Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/8d96f57d5cc79c0c51050bb707c19bf07d2895eb Modified Files -------------- src/backend/optimizer/plan/planner.c | 7 +- src/backend/optimizer/prep/prepunion.c | 478 ++++++++++++-------------------- src/backend/optimizer/util/pathnode.c | 69 ++++- src/include/optimizer/prep.h | 1 - src/test/regress/expected/subselect.out | 48 +++- src/test/regress/expected/union.out | 53 ++-- src/test/regress/sql/subselect.sql | 32 ++- src/test/regress/sql/union.sql | 9 + 8 files changed, 365 insertions(+), 332 deletions(-)
