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Tom Lane 41efb83408 Move resolution of AlternativeSubPlan choices to the planner. ... When commit bd3daddaf introduced AlternativeSubPlans, I had some ambitions towards allowing the choice of subplan to change during execution. That has not happened, or even been thought about, in the ensuing twelve years; so it seems like a failed experiment. So let's rip that out and resolve the choice of subplan at the end of planning (in setrefs.c) rather than during executor startup. This has a number of positive benefits: * Removal of a few hundred lines of executor code, since AlternativeSubPlans need no longer be supported there. * Removal of executor-startup overhead (particularly, initialization of subplans that won't be used). * Removal of incidental costs of having a larger plan tree, such as tree-scanning and copying costs in the plancache; not to mention setrefs.c's own costs of processing the discarded subplans. * EXPLAIN no longer has to print a weird (and undocumented) representation of an AlternativeSubPlan choice; it sees only the subplan actually used. This should mean less confusion for users. * Since setrefs.c knows which subexpression of a plan node it's working on at any instant, it's possible to adjust the estimated number of executions of the subplan based on that. For example, we should usually estimate more executions of a qual expression than a targetlist expression. The implementation used here is pretty simplistic, because we don't want to expend a lot of cycles on the issue; but it's better than ignoring the point entirely, as the executor had to. That last point might possibly result in shifting the choice between hashed and non-hashed EXISTS subplans in a few cases, but in general this patch isn't meant to change planner choices. Since we're doing the resolution so late, it's really impossible to change any plan choices outside the AlternativeSubPlan itself. Patch by me; thanks to David Rowley for review. Discussion: https://postgr.es/m/1992952.1592785225@sss.pgh.pa.us		5 years ago
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Makefile	Split all OBJS style lines in makefiles into one-line-per-entry style.	6 years ago
llvmjit.c	Register llvm_shutdown using on_proc_exit, not before_shmem_exit.	5 years ago
llvmjit_deform.c	Introduce macros for typalign and typstorage constants.	6 years ago
llvmjit_error.cpp	Update copyrights for 2020	6 years ago
llvmjit_expr.c	Move resolution of AlternativeSubPlan choices to the planner.	5 years ago
llvmjit_inline.cpp	llvmjit: Fix building against LLVM 11 by removing unnecessary include.	5 years ago
llvmjit_types.c	Move resolution of AlternativeSubPlan choices to the planner.	5 years ago
llvmjit_wrap.cpp	Update copyrights for 2020	6 years ago