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Provide a planner hook at a suitable place for creating upper-rel Paths.

2016年3月14日 23:23:29 +0000 (19:23 -0400)

In the initial revision of the upper-planner pathification work, the only
available way for an FDW or custom-scan provider to inject Paths
representing post-scan-join processing was to insert them during scan-level
GetForeignPaths or similar processing. While that's not impossible, it'd
require quite a lot of duplicative processing to look forward and see if
the extension would be capable of implementing the whole query. To improve
matters for custom-scan providers, provide a hook function at the point
where the core code is about to start filling in upperrel Paths. At this
point Paths are available for the whole scan/join tree, which should reduce
the amount of redundant effort considerably.

(An alternative design that was suggested was to provide a separate hook
for each post-scan-join processing step, but that seems messy and not
clearly more useful.)

Following our time-honored tradition, there's no documentation for this
hook outside the source code.

As-is, this hook is only meant for custom scan providers, which we can't
assume very much about. A followon patch will implement an FDW callback
to let FDWs do the same thing in a somewhat more structured fashion.

src/backend/optimizer/plan/planner.c patch | blob | blame | history

src/backend/optimizer/prep/prepjointree.c patch | blob | blame | history

src/include/nodes/relation.h patch | blob | blame | history

src/include/optimizer/planner.h patch | blob | blame | history

diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c

index f3a0a44fd889df7bc87532c205e3263f7c23d3ca..d11f44e64d530cb9bb77486d08d276ac8bffea6c 100644 (file)

--- a/src/backend/optimizer/plan/planner.c

+++ b/src/backend/optimizer/plan/planner.c

@@ -62,6 +62,9 @@ int force_parallel_mode = FORCE_PARALLEL_OFF;

/* Hook for plugins to get control in planner() */

planner_hook_type planner_hook = NULL;

+/* Hook for plugins to get control before grouping_planner plans upper rels */

+create_upper_paths_hook_type create_upper_paths_hook = NULL;

/* Expression kind codes for preprocess_expression */

#define EXPRKIND_QUAL 0

@@ -459,6 +462,7 @@ subquery_planner(PlannerGlobal *glob, Query *parse,

root->append_rel_list = NIL;

root->rowMarks = NIL;

memset(root->upper_rels, 0, sizeof(root->upper_rels));

+ memset(root->upper_targets, 0, sizeof(root->upper_targets));

root->processed_tlist = NIL;

root->grouping_map = NULL;

root->minmax_aggs = NIL;

@@ -1736,6 +1740,28 @@ grouping_planner(PlannerInfo *root, bool inheritance_update,

}

+ /*

+ * Save the various upper-rel PathTargets we just computed into

+ * root->upper_targets[]. The core code doesn't use this, but it

+ * provides a convenient place for extensions to get at the info. For

+ * consistency, we save all the intermediate targets, even though some

+ * of the corresponding upperrels might not be needed for this query.

+ */

+ root->upper_targets[UPPERREL_FINAL] = final_target;

+ root->upper_targets[UPPERREL_WINDOW] = sort_input_target;

+ root->upper_targets[UPPERREL_GROUP_AGG] = grouping_target;

+ /*

+ * Let extensions, particularly CustomScan providers, consider

+ * injecting extension Paths into the query's upperrels, where they

+ * will compete with the Paths we create below. We pass the final

+ * scan/join rel because that's not so easily findable from the

+ * PlannerInfo struct; anything else the hook wants to know should be

+ * obtainable via "root".

+ */

+ if (create_upper_paths_hook)

+ (*create_upper_paths_hook) (root, current_rel);

* If we have grouping and/or aggregation, consider ways to implement

* that. We build a new upperrel representing the output of this

diff --git a/src/backend/optimizer/prep/prepjointree.c b/src/backend/optimizer/prep/prepjointree.c

index c8d5c66b396cdde4d144d8539c858bdfdf60061d..75577bce2ca02e56cb010d2161c85c8711967e0f 100644 (file)

--- a/src/backend/optimizer/prep/prepjointree.c

+++ b/src/backend/optimizer/prep/prepjointree.c

@@ -909,6 +909,7 @@ pull_up_simple_subquery(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte,

subroot->append_rel_list = NIL;

subroot->rowMarks = NIL;

memset(subroot->upper_rels, 0, sizeof(subroot->upper_rels));

+ memset(subroot->upper_targets, 0, sizeof(subroot->upper_targets));

subroot->processed_tlist = NIL;

subroot->grouping_map = NULL;

subroot->minmax_aggs = NIL;

diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h

index b48a6183dc2cbedb0aa97d7a0846b57c685abbbd..503269693bac3c1ba23b8668dddb1490ea68a3fb 100644 (file)

--- a/src/include/nodes/relation.h

+++ b/src/include/nodes/relation.h

@@ -263,6 +263,9 @@ typedef struct PlannerInfo

/* Use fetch_upper_rel() to get any particular upper rel */

List *upper_rels[UPPERREL_FINAL + 1]; /* upper-rel RelOptInfos */

+ /* Result tlists chosen by grouping_planner for upper-stage processing */

+ struct PathTarget *upper_targets[UPPERREL_FINAL + 1];

* grouping_planner passes back its final processed targetlist here, for

* use in relabeling the topmost tlist of the finished Plan.

diff --git a/src/include/optimizer/planner.h b/src/include/optimizer/planner.h

index 3fb7cb58cbd77d2eedf6ce00ae40fd048cafb9b2..a95e73fa93b4e36f83dd0c79b8b3b2160ec87729 100644 (file)

--- a/src/include/optimizer/planner.h

+++ b/src/include/optimizer/planner.h

@@ -24,6 +24,11 @@ typedef PlannedStmt *(*planner_hook_type) (Query *parse,

ParamListInfo boundParams);

extern PGDLLIMPORT planner_hook_type planner_hook;

+/* Hook for plugins to get control before grouping_planner plans upper rels */

+typedef void (*create_upper_paths_hook_type) (PlannerInfo *root,

+ RelOptInfo *scan_join_rel);

+extern PGDLLIMPORT create_upper_paths_hook_type create_upper_paths_hook;

extern PlannedStmt *planner(Query *parse, int cursorOptions,

ParamListInfo boundParams);

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