Fix bugs in RelationGetPartitionDispatchInfo.

The previous coding was not quite right for cases involving multiple
levels of partitioning.

Amit Langote

diff --git a/src/backend/catalog/partition.c b/src/backend/catalog/partition.c
index 63d9b13db44aad7e1aaa3ec4cd68f687be30ceac..9980582b777af65838dcca0a7675b9c4ae70be14 100644 (file)
--- a/src/backend/catalog/partition.c
+++ b/src/backend/catalog/partition.c
@@ -950,7 +950,8 @@ RelationGetPartitionDispatchInfo(Relation rel, int lockmode,
               *parted_rels;
    ListCell   *lc;
    int         i,
-               k;
+               k,
+               offset;
 
    /*
     * Lock partitions and make a list of the partitioned ones to prepare
@@ -990,11 +991,19 @@ RelationGetPartitionDispatchInfo(Relation rel, int lockmode,
         */
    }
 
-   /* Generate PartitionDispatch objects for all partitioned tables */
+   /*
+    * We want to create two arrays - one for leaf partitions and another for
+    * partitioned tables (including the root table and internal partitions).
+    * While we only create the latter here, leaf partition array of suitable
+    * objects (such as, ResultRelInfo) is created by the caller using the
+    * list of OIDs we return.  Indexes into these arrays get assigned in a
+    * breadth-first manner, whereby partitions of any given level are placed
+    * consecutively in the respective arrays.
+    */
    pd = (PartitionDispatchData **) palloc(*num_parted *
                                           sizeof(PartitionDispatchData *));
    *leaf_part_oids = NIL;
-   i = k = 0;
+   i = k = offset = 0;
    foreach(lc, parted_rels)
    {
        Relation    partrel = lfirst(lc);
@@ -1010,6 +1019,16 @@ RelationGetPartitionDispatchInfo(Relation rel, int lockmode,
        pd[i]->partdesc = partdesc;
        pd[i]->indexes = (int *) palloc(partdesc->nparts * sizeof(int));
 
+       /*
+        * Indexes corresponding to the internal partitions are multiplied by
+        * -1 to distinguish them from those of leaf partitions.  Encountering
+        * an index >= 0 means we found a leaf partition, which is immediately
+        * returned as the partition we are looking for.  A negative index
+        * means we found a partitioned table, whose PartitionDispatch object
+        * is located at the above index multiplied back by -1.  Using the
+        * PartitionDispatch object, search is continued further down the
+        * partition tree.
+        */
        m = 0;
        for (j = 0; j < partdesc->nparts; j++)
        {
@@ -1023,14 +1042,22 @@ RelationGetPartitionDispatchInfo(Relation rel, int lockmode,
            else
            {
                /*
-                * We can assign indexes this way because of the way
-                * parted_rels has been generated.
+                * offset denotes the number of partitioned tables of upper
+                * levels including those of the current level.  Any partition
+                * of this table must belong to the next level and hence will
+                * be placed after the last partitioned table of this level.
                 */
-               pd[i]->indexes[j] = -(i + 1 + m);
+               pd[i]->indexes[j] = -(1 + offset + m);
                m++;
            }
        }
        i++;
+
+       /*
+        * This counts the number of partitioned tables at upper levels
+        * including those of the current level.
+        */
+       offset += m;
    }
 
    return pd;