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Do ScalarArrayOp estimation correctly when array is a stable expression.

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Most estimation functions apply estimate_expression_value to see if they
can reduce an expression to a constant; the key difference is that it
allows evaluation of stable as well as immutable functions in hopes of
ending up with a simple Const node.  scalararraysel didn't get the memo
though, and neither did gincost_opexpr/gincost_scalararrayopexpr.  Fix
that, and remove a now-unnecessary estimate_expression_value step in the
subsidiary function scalararraysel_containment.

Per complaint from Alexey Klyukin.  Back-patch to 9.3.  The problem
goes back further, but I'm hesitant to change estimation behavior in
long-stable release branches.
This commit is contained in:
Tom Lane
2014-02-21 17:10:46 -05:00
parent 0c5783ff30
commit 77585bce03
2 changed files with 26 additions and 11 deletions
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15
src/backend/utils/adt/array_selfuncs.c
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@ -68,11 +68,13 @@ static int float_compare_desc(const void *key1, const void *key2);
* scalararraysel_containment
* Estimate selectivity of ScalarArrayOpExpr via array containment.
*
* scalararraysel() has already verified that the operator of a
* ScalarArrayOpExpr is the array element type's default equality or
* inequality operator. If we have const =/<> ANY/ALL (array_var)
* then we can estimate the selectivity as though this were an array
* containment operator, array_var op ARRAY[const].
* If we have const =/<> ANY/ALL (array_var) then we can estimate the
* selectivity as though this were an array containment operator,
* array_var op ARRAY[const].
*
* scalararraysel() has already verified that the ScalarArrayOpExpr's operator
* is the array element type's default equality or inequality operator, and
* has aggressively simplified both inputs to constants.
*
* Returns selectivity (0..1), or -1 if we fail to estimate selectivity.
*/
@ -99,9 +101,8 @@ scalararraysel_containment(PlannerInfo *root,
}
/*
* Aggressively reduce leftop to a constant, if possible.
* leftop must be a constant, else punt.
*/
leftop = estimate_expression_value(root, leftop);
if (!IsA(leftop, Const))
{
ReleaseVariableStats(vardata);