Arrange to free planning memory (or most of it, anyway) at completion

of planning.  This should reduce memory requirements for large joins.

diff --git a/src/backend/optimizer/plan/planmain.c b/src/backend/optimizer/plan/planmain.c
index a33d068a385ef01ab1546d33b8e16926f705c371..6b6bc15bda7b5e2dd70705f52e2611cbe31f5ea0 100644 (file)
--- a/src/backend/optimizer/plan/planmain.c
+++ b/src/backend/optimizer/plan/planmain.c
@@ -14,7 +14,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planmain.c,v 1.56 2000/07/24 03:11:01 tgl Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planmain.c,v 1.57 2000/07/27 04:51:04 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -28,6 +28,7 @@
 #include "optimizer/paths.h"
 #include "optimizer/planmain.h"
 #include "optimizer/tlist.h"
+#include "utils/memutils.h"
 
 
 static Plan *subplanner(Query *root, List *flat_tlist, List *qual,
@@ -176,6 +177,9 @@ subplanner(Query *root,
           double tuple_fraction)
 {
    RelOptInfo *final_rel;
+   Plan       *resultplan;
+   MemoryContext mycontext;
+   MemoryContext oldcxt;
    Path       *cheapestpath;
    Path       *presortedpath;
 
@@ -212,6 +216,24 @@ subplanner(Query *root,
     */
    root->query_pathkeys = canonicalize_pathkeys(root, root->query_pathkeys);
 
+   /*
+    * We might allocate quite a lot of storage during planning (due to
+    * constructing lots of Paths), but all of it can be reclaimed after
+    * we generate the finished Plan tree.  Work in a temporary context
+    * to let that happen.  We make the context a child of
+    * TransactionCommandContext so it will be freed if error abort.
+    *
+    * Note: beware of trying to move this up to the start of this routine.
+    * Some of the data structures built above --- notably the pathkey
+    * equivalence sets --- will still be needed after this routine exits.
+    */
+   mycontext = AllocSetContextCreate(TransactionCommandContext,
+                                     "Planner",
+                                     ALLOCSET_DEFAULT_MINSIZE,
+                                     ALLOCSET_DEFAULT_INITSIZE,
+                                     ALLOCSET_DEFAULT_MAXSIZE);
+   oldcxt = MemoryContextSwitchTo(mycontext);
+
    /*
     * Ready to do the primary planning.
     */
@@ -235,7 +257,9 @@ subplanner(Query *root,
        root->query_pathkeys = NIL;     /* signal unordered result */
 
        /* Make childless Result node to evaluate given tlist. */
-       return (Plan *) make_result(flat_tlist, (Node *) qual, (Plan *) NULL);
+       resultplan = (Plan *) make_result(flat_tlist, (Node *) qual,
+                                         (Plan *) NULL);
+       goto plan_built;
    }
 
 #ifdef NOT_USED                    /* fix xfunc */
@@ -295,7 +319,8 @@ subplanner(Query *root,
                              cheapestpath->pathkeys))
    {
        root->query_pathkeys = cheapestpath->pathkeys;
-       return create_plan(root, cheapestpath);
+       resultplan = create_plan(root, cheapestpath);
+       goto plan_built;
    }
 
    /*
@@ -321,7 +346,8 @@ subplanner(Query *root,
        {
            /* Presorted path is cheaper, use it */
            root->query_pathkeys = presortedpath->pathkeys;
-           return create_plan(root, presortedpath);
+           resultplan = create_plan(root, presortedpath);
+           goto plan_built;
        }
        /* otherwise, doing it the hard way is still cheaper */
    }
@@ -334,5 +360,24 @@ subplanner(Query *root,
     * as an aggregate function...)
     */
    root->query_pathkeys = cheapestpath->pathkeys;
-   return create_plan(root, cheapestpath);
+   resultplan = create_plan(root, cheapestpath);
+
+plan_built:
+
+   /*
+    * Must copy the completed plan tree and its pathkeys out of temporary
+    * context.
+    */
+   MemoryContextSwitchTo(oldcxt);
+
+   resultplan = copyObject(resultplan);
+
+   root->query_pathkeys = copyObject(root->query_pathkeys);
+
+   /*
+    * Now we can release the Path storage.
+    */
+   MemoryContextDelete(mycontext);
+
+   return resultplan;
 }