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Use multi-variate MCV lists to estimate ScalarArrayOpExpr

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Commit 8f321bd16c added support for estimating ScalarArrayOpExpr clauses
(IN/ANY) clauses using functional dependencies. There's no good reason
not to support estimation of these clauses using multi-variate MCV lists
too, so this commits implements that. That makes the behavior consistent
and MCV lists can estimate all variants (ANY/ALL, inequalities, ...).

Author: Tomas Vondra
Review: Dean Rasheed
Discussion: https://www.postgresql.org/message-id/flat/13902317.Eha0YfKkKy%40pierred-pdoc
This commit is contained in:
Tomas Vondra
2020-03-14 14:56:37 +01:00
parent 8f321bd16c
commit e83daa7e33
5 changed files with 252 additions and 9 deletions
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111
src/backend/statistics/mcv.c
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@@ -1579,7 +1579,7 @@ mcv_get_match_bitmap(PlannerInfo *root, List *clauses,
OpExpr *expr = (OpExpr *) clause;
FmgrInfo opproc;
/* valid only after examine_opclause_expression returns true */
/* valid only after examine_clause_args returns true */
Var *var;
Const *cst;
bool varonleft;
@@ -1587,7 +1587,7 @@ mcv_get_match_bitmap(PlannerInfo *root, List *clauses,
fmgr_info(get_opcode(expr->opno), &opproc);
/* extract the var and const from the expression */
if (examine_opclause_expression(expr, &var, &cst, &varonleft))
if (examine_clause_args(expr->args, &var, &cst, &varonleft))
{
int idx;
@@ -1652,6 +1652,113 @@ mcv_get_match_bitmap(PlannerInfo *root, List *clauses,
}
}
}
else if (IsA(clause, ScalarArrayOpExpr))
{
ScalarArrayOpExpr *expr = (ScalarArrayOpExpr *) clause;
FmgrInfo opproc;
/* valid only after examine_clause_args returns true */
Var *var;
Const *cst;
bool varonleft;
fmgr_info(get_opcode(expr->opno), &opproc);
/* extract the var and const from the expression */
if (examine_clause_args(expr->args, &var, &cst, &varonleft))
{
int idx;
ArrayType *arrayval;
int16 elmlen;
bool elmbyval;
char elmalign;
int num_elems;
Datum *elem_values;
bool *elem_nulls;
/* ScalarArrayOpExpr has the Var always on the left */
Assert(varonleft);
if (!cst->constisnull)
{
arrayval = DatumGetArrayTypeP(cst->constvalue);
get_typlenbyvalalign(ARR_ELEMTYPE(arrayval),
&elmlen, &elmbyval, &elmalign);
deconstruct_array(arrayval,
ARR_ELEMTYPE(arrayval),
elmlen, elmbyval, elmalign,
&elem_values, &elem_nulls, &num_elems);
}
/* match the attribute to a dimension of the statistic */
idx = bms_member_index(keys, var->varattno);
/*
* Walk through the MCV items and evaluate the current clause.
* We can skip items that were already ruled out, and
* terminate if there are no remaining MCV items that might
* possibly match.
*/
for (i = 0; i < mcvlist->nitems; i++)
{
int j;
bool match = (expr->useOr ? false : true);
MCVItem *item = &mcvlist->items[i];
/*
* When the MCV item or the Const value is NULL we can treat
* this as a mismatch. We must not call the operator because
* of strictness.
*/
if (item->isnull[idx] || cst->constisnull)
{
matches[i] = RESULT_MERGE(matches[i], is_or, false);
continue;
}
/*
* Skip MCV items that can't change result in the bitmap.
* Once the value gets false for AND-lists, or true for
* OR-lists, we don't need to look at more clauses.
*/
if (RESULT_IS_FINAL(matches[i], is_or))
continue;
for (j = 0; j < num_elems; j++)
{
Datum elem_value = elem_values[j];
bool elem_isnull = elem_nulls[j];
bool elem_match;
/* NULL values always evaluate as not matching. */
if (elem_isnull)
{
match = RESULT_MERGE(match, expr->useOr, false);
continue;
}
/*
* Stop evaluating the array elements once we reach
* match value that can't change - ALL() is the same
* as AND-list, ANY() is the same as OR-list.
*/
if (RESULT_IS_FINAL(match, expr->useOr))
break;
elem_match = DatumGetBool(FunctionCall2Coll(&opproc,
var->varcollid,
item->values[idx],
elem_value));
match = RESULT_MERGE(match, expr->useOr, elem_match);
}
/* update the match bitmap with the result */
matches[i] = RESULT_MERGE(matches[i], is_or, match);
}
}
}
else if (IsA(clause, NullTest))
{
NullTest *expr = (NullTest *) clause;