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Avoid making a separate pass over the query to check for partializability.

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It's rather silly to make a separate pass over the tlist + HAVING qual,
and a separate set of visits to the syscache, when get_agg_clause_costs
already has all the required information in hand.  This nets out as less
code as well as fewer cycles.
This commit is contained in:
Tom Lane
2016-06-26 15:55:01 -04:00
parent 19e972d558
commit f1993038a4
4 changed files with 54 additions and 118 deletions
Download Patch File Download Diff File Expand all files Collapse all files

29
src/backend/optimizer/plan/planner.c
View File

@ -110,8 +110,10 @@ static double get_number_of_groups(PlannerInfo *root,
List *rollup_groupclauses);
static void set_grouped_rel_consider_parallel(PlannerInfo *root,
RelOptInfo *grouped_rel,
PathTarget *target);
static Size estimate_hashagg_tablesize(Path *path, AggClauseCosts *agg_costs,
PathTarget *target,
const AggClauseCosts *agg_costs);
static Size estimate_hashagg_tablesize(Path *path,
const AggClauseCosts *agg_costs,
double dNumGroups);
static RelOptInfo *create_grouping_paths(PlannerInfo *root,
RelOptInfo *input_rel,
@ -3207,7 +3209,8 @@ get_number_of_groups(PlannerInfo *root,
*/
static void
set_grouped_rel_consider_parallel(PlannerInfo *root, RelOptInfo *grouped_rel,
PathTarget *target)
PathTarget *target,
const AggClauseCosts *agg_costs)
{
Query *parse = root->parse;
@ -3240,15 +3243,14 @@ set_grouped_rel_consider_parallel(PlannerInfo *root, RelOptInfo *grouped_rel,
return;
/*
* All that's left to check now is to make sure all aggregate functions
* support partial mode. If there's no aggregates then we can skip
* checking that.
* If we have any non-partial-capable aggregates, or if any of them can't
* be serialized, we can't go parallel.
*/
if (!parse->hasAggs)
grouped_rel->consider_parallel = true;
else if (aggregates_allow_partial((Node *) target->exprs) == PAT_ANY &&
aggregates_allow_partial(root->parse->havingQual) == PAT_ANY)
grouped_rel->consider_parallel = true;
if (agg_costs->hasNonPartial || agg_costs->hasNonSerial)
return;
/* OK, consider parallelization */
grouped_rel->consider_parallel = true;
}
/*
@ -3257,7 +3259,7 @@ set_grouped_rel_consider_parallel(PlannerInfo *root, RelOptInfo *grouped_rel,
* require based on the agg_costs, path width and dNumGroups.
*/
static Size
estimate_hashagg_tablesize(Path *path, AggClauseCosts *agg_costs,
estimate_hashagg_tablesize(Path *path, const AggClauseCosts *agg_costs,
double dNumGroups)
{
Size hashentrysize;
@ -3411,7 +3413,8 @@ create_grouping_paths(PlannerInfo *root,
* going to be safe to do so.
*/
if (input_rel->partial_pathlist != NIL)
set_grouped_rel_consider_parallel(root, grouped_rel, target);
set_grouped_rel_consider_parallel(root, grouped_rel,
target, &agg_costs);
/*
* Determine whether it's possible to perform sort-based implementations

118
src/backend/optimizer/util/clauses.c
View File

@ -52,10 +52,6 @@
#include "utils/syscache.h"
#include "utils/typcache.h"
typedef struct
{
PartialAggType allowedtype;
} partial_agg_context;
typedef struct
{
@ -98,8 +94,6 @@ typedef struct
bool allow_restricted;
} has_parallel_hazard_arg;
static bool aggregates_allow_partial_walker(Node *node,
partial_agg_context *context);
static bool contain_agg_clause_walker(Node *node, void *context);
static bool get_agg_clause_costs_walker(Node *node,
get_agg_clause_costs_context *context);
@ -403,81 +397,6 @@ make_ands_implicit(Expr *clause)
* Aggregate-function clause manipulation
*****************************************************************************/
/*
* aggregates_allow_partial
* Recursively search for Aggref clauses and determine the maximum
* level of partial aggregation which can be supported.
*/
PartialAggType
aggregates_allow_partial(Node *clause)
{
partial_agg_context context;
/* initially any type is okay, until we find Aggrefs which say otherwise */
context.allowedtype = PAT_ANY;
if (!aggregates_allow_partial_walker(clause, &context))
return context.allowedtype;
return context.allowedtype;
}
static bool
aggregates_allow_partial_walker(Node *node, partial_agg_context *context)
{
if (node == NULL)
return false;
if (IsA(node, Aggref))
{
Aggref *aggref = (Aggref *) node;
HeapTuple aggTuple;
Form_pg_aggregate aggform;
Assert(aggref->agglevelsup == 0);
/*
* We can't perform partial aggregation with Aggrefs containing a
* DISTINCT or ORDER BY clause.
*/
if (aggref->aggdistinct || aggref->aggorder)
{
context->allowedtype = PAT_DISABLED;
return true; /* abort search */
}
aggTuple = SearchSysCache1(AGGFNOID,
ObjectIdGetDatum(aggref->aggfnoid));
if (!HeapTupleIsValid(aggTuple))
elog(ERROR, "cache lookup failed for aggregate %u",
aggref->aggfnoid);
aggform = (Form_pg_aggregate) GETSTRUCT(aggTuple);
/*
* If there is no combine function, then partial aggregation is not
* possible.
*/
if (!OidIsValid(aggform->aggcombinefn))
{
ReleaseSysCache(aggTuple);
context->allowedtype = PAT_DISABLED;
return true; /* abort search */
}
/*
* If we find any aggs with an internal transtype then we must check
* whether these have serialization/deserialization functions;
* otherwise, we set the maximum allowed type to PAT_INTERNAL_ONLY.
*/
if (aggform->aggtranstype == INTERNALOID &&
(!OidIsValid(aggform->aggserialfn) ||
!OidIsValid(aggform->aggdeserialfn)))
context->allowedtype = PAT_INTERNAL_ONLY;
ReleaseSysCache(aggTuple);
return false; /* continue searching */
}
return expression_tree_walker(node, aggregates_allow_partial_walker,
(void *) context);
}
/*
* contain_agg_clause
* Recursively search for Aggref/GroupingFunc nodes within a clause.
@ -529,8 +448,9 @@ contain_agg_clause_walker(Node *node, void *context)
*
* We count the nodes, estimate their execution costs, and estimate the total
* space needed for their transition state values if all are evaluated in
* parallel (as would be done in a HashAgg plan). See AggClauseCosts for
* the exact set of statistics collected.
* parallel (as would be done in a HashAgg plan). Also, we check whether
* partial aggregation is feasible. See AggClauseCosts for the exact set
* of statistics collected.
*
* In addition, we mark Aggref nodes with the correct aggtranstype, so
* that that doesn't need to be done repeatedly. (That makes this function's
@ -616,10 +536,40 @@ get_agg_clause_costs_walker(Node *node, get_agg_clause_costs_context *context)
aggref->aggtranstype = aggtranstype;
}
/* count it; note ordered-set aggs always have nonempty aggorder */
/*
* Count it, and check for cases requiring ordered input. Note that
* ordered-set aggs always have nonempty aggorder. Any ordered-input
* case also defeats partial aggregation.
*/
costs->numAggs++;
if (aggref->aggorder != NIL || aggref->aggdistinct != NIL)
{
costs->numOrderedAggs++;
costs->hasNonPartial = true;
}
/*
* Check whether partial aggregation is feasible, unless we already
* found out that we can't do it.
*/
if (!costs->hasNonPartial)
{
/*
* If there is no combine function, then partial aggregation is
* not possible.
*/
if (!OidIsValid(aggcombinefn))
costs->hasNonPartial = true;
/*
* If we have any aggs with transtype INTERNAL then we must check
* whether they have serialization/deserialization functions; if
* not, we can't serialize partial-aggregation results.
*/
else if (aggtranstype == INTERNALOID &&
(!OidIsValid(aggserialfn) || !OidIsValid(aggdeserialfn)))
costs->hasNonSerial = true;
}
/*
* Add the appropriate component function execution costs to