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Use a hash table to speed up NOT IN(values)

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Similar to 50e17ad28, which allowed hash tables to be used for IN clauses
with a set of constants, here we add the same feature for NOT IN clauses.

NOT IN evaluates the same as: WHERE a <> v1 AND a <> v2 AND a <> v3.
Obviously, if we're using a hash table we must be exactly equivalent to
that and return the same result taking into account that either side of
the condition could contain a NULL.  This requires a little bit of
special handling to make work with the hash table version.

When processing NOT IN, the ScalarArrayOpExpr's operator will be the <>
operator.  To be able to build and lookup a hash table we must use the
<>'s negator operator.  The planner checks if that exists and is hashable
and sets the relevant fields in ScalarArrayOpExpr to instruct the executor
to use hashing.

Author: David Rowley, James Coleman
Reviewed-by: James Coleman, Zhihong Yu
Discussion: https://postgr.es/m/CAApHDvoF1mum_FRk6D621edcB6KSHBi2+GAgWmioj5AhOu2vwQ@mail.gmail.com
This commit is contained in:
David Rowley
2021-07-07 16:29:17 +12:00
parent d854720df6
commit 29f45e299e
16 changed files with 242 additions and 29 deletions
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17
src/backend/executor/execExprInterp.c
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@ -3493,6 +3493,7 @@ ExecEvalHashedScalarArrayOp(ExprState *state, ExprEvalStep *op, ExprContext *eco
{
ScalarArrayOpExprHashTable *elements_tab = op->d.hashedscalararrayop.elements_tab;
FunctionCallInfo fcinfo = op->d.hashedscalararrayop.fcinfo_data;
bool inclause = op->d.hashedscalararrayop.inclause;
bool strictfunc = op->d.hashedscalararrayop.finfo->fn_strict;
Datum scalar = fcinfo->args[0].value;
bool scalar_isnull = fcinfo->args[0].isnull;
@ -3596,7 +3597,12 @@ ExecEvalHashedScalarArrayOp(ExprState *state, ExprEvalStep *op, ExprContext *eco
/* Check the hash to see if we have a match. */
hashfound = NULL != saophash_lookup(elements_tab->hashtab, scalar);
result = BoolGetDatum(hashfound);
/* the result depends on if the clause is an IN or NOT IN clause */
if (inclause)
result = BoolGetDatum(hashfound); /* IN */
else
result = BoolGetDatum(!hashfound); /* NOT IN */
resultnull = false;
/*
@ -3605,7 +3611,7 @@ ExecEvalHashedScalarArrayOp(ExprState *state, ExprEvalStep *op, ExprContext *eco
* hashtable, but instead marked if we found any when building the table
* in has_nulls.
*/
if (!DatumGetBool(result) && op->d.hashedscalararrayop.has_nulls)
if (!hashfound && op->d.hashedscalararrayop.has_nulls)
{
if (strictfunc)
{
@ -3633,6 +3639,13 @@ ExecEvalHashedScalarArrayOp(ExprState *state, ExprEvalStep *op, ExprContext *eco
result = op->d.hashedscalararrayop.fn_addr(fcinfo);
resultnull = fcinfo->isnull;
/*
* Reverse the result for NOT IN clauses since the above function
* is the equality function and we need not-equals.
*/
if (!inclause)
result = !result;
}
}