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Fix run-time partition pruning code to handle NULL values properly.

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The previous coding just ignored pruning constraints that compare a
partition key to a null-valued expression.  This is silly, since really
what we can do there is conclude that all partitions are rejected: the
pruning operator is known strict so the comparison must always fail.

This also fixes the logic to not ignore constisnull for a Const comparison
value.  That's probably an unreachable case, since the planner would
normally have simplified away a strict operator with a constant-null input.
But this code has no business assuming that.

David Rowley, per a gripe from me

Discussion: https://postgr.es/m/26279.1528670981@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2018-06-11 12:08:09 -04:00
parent 387543f7bd
commit be3d90026a
3 changed files with 53 additions and 13 deletions
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48
src/backend/partitioning/partprune.c
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@@ -170,7 +170,8 @@ static PruneStepResult *perform_pruning_combine_step(PartitionPruneContext *cont
static bool match_boolean_partition_clause(Oid partopfamily, Expr *clause,
Expr *partkey, Expr **outconst);
static bool partkey_datum_from_expr(PartitionPruneContext *context,
Expr *expr, int stateidx, Datum *value);
Expr *expr, int stateidx,
Datum *value, bool *isnull);
/*
@@ -184,8 +185,9 @@ static bool partkey_datum_from_expr(PartitionPruneContext *context,
* indexes.
*
* If no non-Const expressions are being compared to the partition key in any
* of the 'partitioned_rels', then we return NIL. In such a case run-time
* partition pruning would be useless, since the planner did it already.
* of the 'partitioned_rels', then we return NIL to indicate no run-time
* pruning should be performed. Run-time pruning would be useless, since the
* pruning done during planning will have pruned everything that can be.
*/
List *
make_partition_pruneinfo(PlannerInfo *root, List *partition_rels,
@@ -2835,14 +2837,33 @@ perform_pruning_base_step(PartitionPruneContext *context,
Expr *expr;
int stateidx;
Datum datum;
bool isnull;
expr = lfirst(lc1);
stateidx = PruneCxtStateIdx(context->partnatts,
opstep->step.step_id, keyno);
if (partkey_datum_from_expr(context, expr, stateidx, &datum))
if (partkey_datum_from_expr(context, expr, stateidx,
&datum, &isnull))
{
Oid cmpfn;
/*
* Since we only allow strict operators in pruning steps, any
* null-valued comparison value must cause the comparison to
* fail, so that no partitions could match.
*/
if (isnull)
{
PruneStepResult *result;
result = (PruneStepResult *) palloc(sizeof(PruneStepResult));
result->bound_offsets = NULL;
result->scan_default = false;
result->scan_null = false;
return result;
}
/*
* If we're going to need a different comparison function than
* the one cached in the PartitionKey, we'll need to look up
@@ -3072,8 +3093,8 @@ match_boolean_partition_clause(Oid partopfamily, Expr *clause, Expr *partkey,
* Evaluate expression for potential partition pruning
*
* Evaluate 'expr', whose ExprState is stateidx of the context exprstate
* array; set *value to the resulting Datum. Return true if evaluation was
* possible, otherwise false.
* array; set *value and *isnull to the resulting Datum and nullflag.
* Return true if evaluation was possible, otherwise false.
*
* Note that the evaluated result may be in the per-tuple memory context of
* context->planstate->ps_ExprContext, and we may have leaked other memory
@@ -3082,11 +3103,16 @@ match_boolean_partition_clause(Oid partopfamily, Expr *clause, Expr *partkey,
*/
static bool
partkey_datum_from_expr(PartitionPruneContext *context,
Expr *expr, int stateidx, Datum *value)
Expr *expr, int stateidx,
Datum *value, bool *isnull)
{
if (IsA(expr, Const))
{
*value = ((Const *) expr)->constvalue;
/* We can always determine the value of a constant */
Const *con = (Const *) expr;
*value = con->constvalue;
*isnull = con->constisnull;
return true;
}
else
@@ -3105,14 +3131,10 @@ partkey_datum_from_expr(PartitionPruneContext *context,
{
ExprState *exprstate;
ExprContext *ectx;
bool isNull;
exprstate = context->exprstates[stateidx];
ectx = context->planstate->ps_ExprContext;
*value = ExecEvalExprSwitchContext(exprstate, ectx, &isNull);
if (isNull)
return false;
*value = ExecEvalExprSwitchContext(exprstate, ectx, isnull);
return true;
}
}