Re: [PR] Optimize DISTINCT, ORDER BY and DISTINCT ON when Aggregation without Group By. [cloudberry]

["avamingli (via GitHub)" <gi...@apache.org>]

avamingli commented on code in PR #685:
URL: https://github.com/apache/cloudberry/pull/685#discussion_r1867398373


##########
src/backend/optimizer/plan/transform.c:
##########
@@ -520,3 +521,124 @@ replace_sirvf_rte(Query *query, RangeTblEntry *rte)
 
 	return rte;
 }
+
+/*
+ * Does query has SRFs, or WITH ORDINALITY?
+ */
+bool query_has_srf(Query *query)
+{
+	if (query->hasTargetSRFs)
+	{
+		return true;
+	}
+
+	/* Double check for subquery. */
+	if (expression_returns_set( (Node *) query->targetList))
+	{
+		return true;
+	}
+
+	ListCell *lcrte = NULL;
+	foreach (lcrte, query->rtable)

Review Comment:
   Fixed, as well as JOIN of SRFs:
   
   ```sql
   explain(verbose, costs off)
   select distinct(count(a)) from generate_series(0, 1) as a;
                                                           QUERY PLAN                                                         
   ---------------------------------------------------------------------------------------------------------------------------
    Aggregate
      Output: count(a)
      ->  Function Scan on pg_catalog.generate_series a
            Output: a
            Function Call: generate_series(0, 1)
    Settings: enable_hashagg = 'on', enable_sort = 'on', gp_statistics_pullup_from_child_partition = 'off', optimizer = 'off'
    Optimizer: Postgres query optimizer
   (7 rows)
   
   explain(verbose, costs off)
   select distinct(count(*)) from generate_series(0, 1) a join generate_series(0, 2) b on true;
                                                           QUERY PLAN                                                         
   ---------------------------------------------------------------------------------------------------------------------------
    Aggregate
      Output: count(*)
      ->  Nested Loop
            ->  Function Scan on pg_catalog.generate_series a
                  Output: a.a
                  Function Call: generate_series(0, 1)
            ->  Function Scan on pg_catalog.generate_series b
                  Output: b.b
                  Function Call: generate_series(0, 2)
    Settings: enable_hashagg = 'on', enable_sort = 'on', gp_statistics_pullup_from_child_partition = 'off', optimizer = 'off'
    Optimizer: Postgres query optimizer
   (11 rows)
   
   ```



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