Prune real-time branch of deep hierarchical caggs

A single application of ts_transform_time_bucket_comparison() strips
only the outermost time_bucket() from a comparison. In a hierarchical
continuous aggregate the bucket input is itself another time_bucket()
call. The real-time branch could not be proven empty and the refresh
re-scanned the whole raw un-materialized tail of the base hypertable.

Add ts_transform_nested_time_bucket_comparison(), which applies the
single-level transform repeatedly until the bound is expressed on the
raw column. Only the original qual and the fully reduced qual are kept;
the intermediate levels have no consumer.

Fixes: #10071

Author: melihmutlu

.unreleased/pr_10175

@@ -0,0 +1,2 @@
+Fixes: #10071 Prune the real-time branch of hierarchical continuous aggregates at any nesting depth
+Thanks: @viniciusrsouza for reporting the issue

src/nodes/chunk_append/exec.c

@@ -1001,7 +1001,7 @@ ts_constify_restrictinfos(PlannerInfo *root, List *restrictinfos)
 			 * transformations again. This might allow us to exclude chunks
 			 * based on a parameterized time_bucket expression.
 			 */
-			Expr *additional_clause = ts_transform_time_bucket_comparison(constified);
+			Expr *additional_clause = ts_transform_nested_time_bucket_comparison(constified);
 			if (additional_clause != NULL)
 			{
 				/*

src/planner/expand_hypertable.c

@@ -731,6 +731,32 @@ ts_transform_time_bucket_comparison(Expr *node)
 	return &op->xpr;
 }
 
+/*
+ * Fully unwrap a (possibly nested) time_bucket() comparison by applying the
+ * single-level transform repeatedly until the bound reaches the raw column.
+ *
+ * ts_transform_time_bucket_comparison() only strips the outermost time_bucket().
+ * In hierarchical continuous aggregates the time_bucket() input column can be
+ * itself another time_bucket() call.
+ *
+ * Used both during hypertable expansion and from the chunk-append executor's
+ * runtime constification.
+ */
+Expr *
+ts_transform_nested_time_bucket_comparison(Expr *qual)
+{
+	Expr *nested = ts_transform_time_bucket_comparison(qual);
+	Expr *transformed = NULL;
+
+	while (nested != NULL)
+	{
+		transformed = nested;
+		nested = ts_transform_time_bucket_comparison(transformed);
+	}
+
+	return transformed;
+}
+
 /*
  * Since baserestrictinfo is not yet set by the planner, we have to derive
  * it ourselves. It's safe for us to miss some restrict info clauses (this
@@ -784,7 +810,7 @@ process_quals(Node *quals, CollectQualCtx *ctx, bool is_outer_join)
 				 * check for time_bucket comparisons
 				 * time_bucket(Const, time_colum) > Const
 				 */
-				Expr *transformed = ts_transform_time_bucket_comparison(qual);
+				Expr *transformed = ts_transform_nested_time_bucket_comparison(qual);
 				if (transformed != NULL)
 				{
 					/*
@@ -835,7 +861,7 @@ timebucket_annotate(Node *quals, CollectQualCtx *ctx)
 		 * check for time_bucket comparisons
 		 * time_bucket(Const, time_colum) > Const
 		 */
-		Expr *transformed = ts_transform_time_bucket_comparison(qual);
+		Expr *transformed = ts_transform_nested_time_bucket_comparison(qual);
 		if (transformed != NULL)
 		{
 			/*
@@ -1054,7 +1080,7 @@ get_simplified_restrictions(PlannerInfo *root, List *restrictions)
 				 * check for time_bucket comparisons
 				 * time_bucket(Const, time_colum) > Const
 				 */
-				Expr *transformed = ts_transform_time_bucket_comparison(qual);
+				Expr *transformed = ts_transform_nested_time_bucket_comparison(qual);
 				if (transformed != NULL)
 				{
 					/*

src/planner/planner.h

@@ -97,6 +97,7 @@ extern void ts_plan_expand_hypertable_chunks(Hypertable *ht, PlannerInfo *root,
 											 bool include_osm);
 extern void ts_plan_expand_timebucket_annotate(PlannerInfo *root, RelOptInfo *rel);
 extern Expr *ts_transform_time_bucket_comparison(Expr *);
+extern Expr *ts_transform_nested_time_bucket_comparison(Expr *);
 extern Node *ts_constify_now(PlannerInfo *root, List *rtable, Node *node);
 extern void ts_planner_constraint_cleanup(PlannerInfo *root, RelOptInfo *rel);
 extern Node *ts_add_space_constraints(PlannerInfo *root, List *rtable, Node *node);