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Improve handling of CustomPath/CustomPlan(State) children.

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Allow CustomPath to have a list of paths, CustomPlan a list of plans,
and CustomPlanState a list of planstates known to the core system, so
that custom path/plan providers can more reasonably use this
infrastructure for nodes with multiple children.

KaiGai Kohei, per a design suggestion from Tom Lane, with some
further kibitzing by me.
This commit is contained in:
Robert Haas
2015-06-26 09:40:47 -04:00
parent 4b8e24b9ad
commit 5ca611841b
8 changed files with 77 additions and 7 deletions
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10
doc/src/sgml/custom-scan.sgml
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@ -60,6 +60,7 @@ typedef struct CustomPath
{
Path path;
uint32 flags;
List *custom_paths;
List *custom_private;
const CustomPathMethods *methods;
} CustomPath;
@ -73,6 +74,9 @@ typedef struct CustomPath
<literal>CUSTOMPATH_SUPPORT_BACKWARD_SCAN</> if the custom path can support
a backward scan and <literal>CUSTOMPATH_SUPPORT_MARK_RESTORE</> if it
can support mark and restore. Both capabilities are optional.
An optional <structfield>custom_paths</> is a list of <structname>Path</>
nodes used by this custom-path node; these will be transformed into
<structname>Plan</> nodes by planner.
<structfield>custom_private</> can be used to store the custom path's
private data. Private data should be stored in a form that can be handled
by <literal>nodeToString</>, so that debugging routines that attempt to
@ -112,7 +116,8 @@ Plan *(*PlanCustomPath) (PlannerInfo *root,
RelOptInfo *rel,
CustomPath *best_path,
List *tlist,
List *clauses);
List *clauses,
List *custom_plans);
</programlisting>
Convert a custom path to a finished plan. The return value will generally
be a <literal>CustomScan</> object, which the callback must allocate and
@ -145,6 +150,7 @@ typedef struct CustomScan
{
Scan scan;
uint32 flags;
List *custom_plans;
List *custom_exprs;
List *custom_private;
List *custom_scan_tlist;
@ -159,6 +165,8 @@ typedef struct CustomScan
estimated costs, target lists, qualifications, and so on.
<structfield>flags</> is a bitmask with the same meaning as in
<structname>CustomPath</>.
<structfield>custom_plans</> can be used to store child
<structname>Plan</> nodes.
<structfield>custom_exprs</> should be used to
store expression trees that will need to be fixed up by
<filename>setrefs.c</> and <filename>subselect.c</>, while