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Invent recursive_worktable_factor GUC to replace hard-wired constant.

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Up to now, the planner estimated the size of a recursive query's
worktable as 10 times the size of the non-recursive term.  It's hard
to see how to do significantly better than that automatically, but
we can give users control over the multiplier to allow tuning for
specific use-cases.  The default behavior remains the same.

Simon Riggs

Discussion: https://postgr.es/m/CANbhV-EuaLm4H3g0+BSTYHEGxJj3Kht0R+rJ8vT57Dejnh=_nA@mail.gmail.com
This commit is contained in:
Tom Lane
2022-03-24 11:47:41 -04:00
parent a47651447f
commit 0bd7af082a
6 changed files with 44 additions and 3 deletions
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2
src/include/optimizer/cost.h
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@@ -29,6 +29,8 @@
#define DEFAULT_PARALLEL_TUPLE_COST 0.1
#define DEFAULT_PARALLEL_SETUP_COST 1000.0
/* defaults for non-Cost parameters */
#define DEFAULT_RECURSIVE_WORKTABLE_FACTOR 10.0
#define DEFAULT_EFFECTIVE_CACHE_SIZE 524288 /* measured in pages */
typedef enum

1
src/include/optimizer/optimizer.h
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@@ -91,6 +91,7 @@ extern PGDLLIMPORT double cpu_index_tuple_cost;
extern PGDLLIMPORT double cpu_operator_cost;
extern PGDLLIMPORT double parallel_tuple_cost;
extern PGDLLIMPORT double parallel_setup_cost;
extern PGDLLIMPORT double recursive_worktable_factor;
extern PGDLLIMPORT int effective_cache_size;
extern double clamp_row_est(double nrows);