Replace the sorted array of GUC variables with a hash table

Enterprise / PostgreSQL - Tom Lane [sss.pgh.pa.us] - 14 October 2022 16:26 UTC

This gets rid of bsearch() in favor of hashed lookup. The main advantage is that it becomes far cheaper to add new GUCs, since we needn't re-sort the pointer array. Adding N new GUCs had been O(N^2 log N), but now it's closer to O(N). We need to sort only in SHOW ALL and equivalent functions, which are hopefully not performance-critical to anybody.

Also, merge GetNumConfigOptions() into get_guc_variables(), because in a world where the set of GUCs isn't fairly static you really want to consider those two results as tied together not independent.

Discussion: https://postgr.es/m/2982579.1662416866@sss.pgh.pa.us

3057465acf Replace the sorted array of GUC variables with a hash table.
src/backend/utils/misc/guc.c | 385 ++++++++++++++++++++++-------------
src/backend/utils/misc/guc_funcs.c | 39 ++--
src/backend/utils/misc/help_config.c | 5 +-
src/include/utils/guc.h | 1 -
src/include/utils/guc_tables.h | 2 +-
5 files changed, 272 insertions(+), 160 deletions(-)

Upstream: git.postgresql.org


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