Fix query pullup issue with WindowClause runCondition

94985c210 added code to detect when WindowFuncs were monotonic and
allowed additional quals to be "pushed down" into the subquery to be
used as WindowClause runConditions in order to short-circuit execution
in nodeWindowAgg.c.

The Node representation of runConditions wasn't well selected and
because we do qual pushdown before planning the subquery, the planning
of the subquery could perform subquery pull-up of nested subqueries.
For WindowFuncs with args, the arguments could be changed after pushing
the qual down to the subquery.

This was made more difficult by the fact that the code duplicated the
WindowFunc inside an OpExpr to include in the WindowClauses runCondition
field.  This could result in duplication of subqueries and a pull-up of
such a subquery could result in another initplan parameter being issued
for the 2nd version of the subplan.  This could result in errors such as:

ERROR:  WindowFunc not found in subplan target lists

To fix this, we change the node representation of these run conditions
and instead of storing an OpExpr containing the WindowFunc in a list
inside WindowClause, we now store a new node type named
WindowFuncRunCondition within a new field in the WindowFunc.  These get
transformed into OpExprs later in planning once subquery pull-up has been
performed.

This problem did exist in v15 and v16, but that was fixed by 9d36b883b
and e5d20bbd.

Cat version bump due to new node type and modifying WindowFunc struct.

Bug: #18305
Reported-by: Zuming Jiang
Discussion: https://postgr.es/m/18305-33c49b4c830b37b3%40postgresql.org

1 files changed, 30 insertions, 0 deletions

diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 43f5766d732..4830efc5738 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -575,6 +575,8 @@ typedef struct WindowFunc
 	List	   *args;
 	/* FILTER expression, if any */
 	Expr	   *aggfilter;
+	/* List of WindowFuncRunConditions to help short-circuit execution */
+	List	   *runCondition pg_node_attr(query_jumble_ignore);
 	/* index of associated WindowClause */
 	Index		winref;
 	/* true if argument list was really '*' */
@@ -586,6 +588,34 @@ typedef struct WindowFunc
 } WindowFunc;
 
 /*
+ * WindowFuncRunCondition
+ *
+ * Represents intermediate OpExprs which will be used by WindowAgg to
+ * short-circuit execution.
+ */
+typedef struct WindowFuncRunCondition
+{
+	Expr		xpr;
+
+	/* PG_OPERATOR OID of the operator */
+	Oid			opno;
+	/* OID of collation that operator should use */
+	Oid			inputcollid pg_node_attr(query_jumble_ignore);
+
+	/*
+	 * true of WindowFunc belongs on the left of the resulting OpExpr or false
+	 * if the WindowFunc is on the right.
+	 */
+	bool		wfunc_left;
+
+	/*
+	 * The Expr being compared to the WindowFunc to use in the OpExpr in the
+	 * WindowAgg's runCondition
+	 */
+	Expr	   *arg;
+} WindowFuncRunCondition;
+
+/*
  * MergeSupportFunc
  *
  * A MergeSupportFunc is a merge support function expression that can only