From 5fc37e297bdda371b8e806eb787da413aa2636ba Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9s=20Taylor?= <andres@planetscale.com>
Date: Wed, 16 Oct 2024 16:28:39 +0200
Subject: [PATCH] bugfix: add HAVING columns inside derived tables (#16976)

Signed-off-by: Andres Taylor <andres@planetscale.com>
---
 .../operators/horizon_expanding.go            |  6 ++
 .../planbuilder/testdata/aggr_cases.json      | 76 +++++++++++++++----
 2 files changed, 67 insertions(+), 15 deletions(-)

diff --git a/go/vt/vtgate/planbuilder/operators/horizon_expanding.go b/go/vt/vtgate/planbuilder/operators/horizon_expanding.go
index a2f0799c547..bf7e95f5a17 100644
--- a/go/vt/vtgate/planbuilder/operators/horizon_expanding.go
+++ b/go/vt/vtgate/planbuilder/operators/horizon_expanding.go
@@ -90,6 +90,12 @@ func expandSelectHorizon(ctx *plancontext.PlanningContext, horizon *Horizon, sel
 		for _, order := range horizon.Query.GetOrderBy() {
 			qp.addDerivedColumn(ctx, order.Expr)
 		}
+		sel, isSel := horizon.Query.(*sqlparser.Select)
+		if isSel && sel.Having != nil {
+			for _, pred := range sqlparser.SplitAndExpression(nil, sel.Having.Expr) {
+				qp.addDerivedColumn(ctx, pred)
+			}
+		}
 	}
 
 	op, err := createProjectionFromSelect(ctx, horizon)
diff --git a/go/vt/vtgate/planbuilder/testdata/aggr_cases.json b/go/vt/vtgate/planbuilder/testdata/aggr_cases.json
index 127dd2c4837..bf12cd7b884 100644
--- a/go/vt/vtgate/planbuilder/testdata/aggr_cases.json
+++ b/go/vt/vtgate/planbuilder/testdata/aggr_cases.json
@@ -571,6 +571,35 @@
       ]
     }
   },
+  {
+    "comment": "using HAVING inside a derived table still produces viable plans",
+    "query": "select id from (select id from user group by id having (count(user.id) = 2) limit 2 offset 0) subquery_for_limit",
+    "plan": {
+      "QueryType": "SELECT",
+      "Original": "select id from (select id from user group by id having (count(user.id) = 2) limit 2 offset 0) subquery_for_limit",
+      "Instructions": {
+        "OperatorType": "Limit",
+        "Count": "2",
+        "Offset": "0",
+        "Inputs": [
+          {
+            "OperatorType": "Route",
+            "Variant": "Scatter",
+            "Keyspace": {
+              "Name": "user",
+              "Sharded": true
+            },
+            "FieldQuery": "select id from (select id, count(`user`.id) = 2 from `user` where 1 != 1 group by id) as subquery_for_limit where 1 != 1",
+            "Query": "select id from (select id, count(`user`.id) = 2 from `user` group by id having count(`user`.id) = 2) as subquery_for_limit limit 2",
+            "Table": "`user`"
+          }
+        ]
+      },
+      "TablesUsed": [
+        "user.user"
+      ]
+    }
+  },
   {
     "comment": "sum with distinct no unique vindex",
     "query": "select col1, sum(distinct col2) from user group by col1",
@@ -3613,25 +3642,42 @@
       "QueryType": "SELECT",
       "Original": "select * from (select id from user having count(*) = 1) s",
       "Instructions": {
-        "OperatorType": "Filter",
-        "Predicate": "count(*) = 1",
-        "ResultColumns": 1,
+        "OperatorType": "SimpleProjection",
+        "ColumnNames": [
+          "0:id"
+        ],
+        "Columns": "0",
         "Inputs": [
           {
-            "OperatorType": "Aggregate",
-            "Variant": "Scalar",
-            "Aggregates": "any_value(0) AS id, sum_count_star(1) AS count(*)",
+            "OperatorType": "Projection",
+            "Expressions": [
+              ":0 as id",
+              "count(*) = 1 as count(*) = 1"
+            ],
             "Inputs": [
               {
-                "OperatorType": "Route",
-                "Variant": "Scatter",
-                "Keyspace": {
-                  "Name": "user",
-                  "Sharded": true
-                },
-                "FieldQuery": "select id, count(*) from `user` where 1 != 1",
-                "Query": "select id, count(*) from `user`",
-                "Table": "`user`"
+                "OperatorType": "Filter",
+                "Predicate": "count(*) = 1",
+                "Inputs": [
+                  {
+                    "OperatorType": "Aggregate",
+                    "Variant": "Scalar",
+                    "Aggregates": "any_value(0) AS id, sum_count_star(1) AS count(*), any_value(2)",
+                    "Inputs": [
+                      {
+                        "OperatorType": "Route",
+                        "Variant": "Scatter",
+                        "Keyspace": {
+                          "Name": "user",
+                          "Sharded": true
+                        },
+                        "FieldQuery": "select id, count(*), 1 from `user` where 1 != 1",
+                        "Query": "select id, count(*), 1 from `user`",
+                        "Table": "`user`"
+                      }
+                    ]
+                  }
+                ]
               }
             ]
           }