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Remove replacement selection sort.

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At the time replacement_sort_tuples was introduced, there were still
cases where replacement selection sort noticeably outperformed using
quicksort even for the first run.  However, those cases seem to have
evaporated as a result of further improvements made since that time
(and perhaps also advances in CPU technology).  So remove replacement
selection and the controlling GUC entirely.  This makes tuplesort.c
noticeably simpler and probably paves the way for further
optimizations someone might want to do later.

Peter Geoghegan, with review and testing by Tomas Vondra and me.

Discussion: https://postgr.es/m/CAH2-WzmmNjG_K0R9nqYwMq3zjyJJK+hCbiZYNGhAy-Zyjs64GQ@mail.gmail.com
This commit is contained in:
Robert Haas
2017-09-29 10:20:44 -04:00
parent d2773f9bcd
commit 8b304b8b72
9 changed files with 52 additions and 448 deletions
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src/backend/utils/init/globals.c
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@@ -112,7 +112,6 @@ bool enableFsync = true;
bool allowSystemTableMods = false;
int work_mem = 1024;
int maintenance_work_mem = 16384;
int replacement_sort_tuples = 150000;
/*
* Primary determinants of sizes of shared-memory structures.