Set parsed comments in operator for subqueries (#18369)

go/vt/vtgate/planbuilder/operators/subquery_planning.go

@@ -551,6 +551,9 @@ func tryMergeSubqueryWithOuter(ctx *plancontext.PlanningContext, subQuery *SubQu
 	if !subQuery.IsArgument {
 		op.Source = newFilter(outer.Source, subQuery.Original)
 	}
+	if outer.Comments != nil {
+		op.Comments = outer.Comments
+	}
 	ctx.MergedSubqueries = append(ctx.MergedSubqueries, subQuery.originalSubquery)
 	return op, Rewrote("merged subquery with outer")
 }

go/vt/vtgate/planbuilder/testdata/select_cases.json

@@ -985,6 +985,74 @@
     },
     "skip_e2e": true
   },
+  {
+    "comment": "Comments with subquery",
+    "query": "select /* comment */ user.col from user where id IN (select id from user where id > 1 and id < 10)",
+    "plan": {
+      "Type": "Scatter",
+      "QueryType": "SELECT",
+      "Original": "select /* comment */ user.col from user where id IN (select id from user where id > 1 and id < 10)",
+      "Instructions": {
+        "OperatorType": "Route",
+        "Variant": "Scatter",
+        "Keyspace": {
+          "Name": "user",
+          "Sharded": true
+        },
+        "FieldQuery": "select `user`.col from `user` where 1 != 1",
+        "Query": "select /* comment */ `user`.col from `user` where id in (select id from `user` where id > 1 and id < 10)"
+      },
+      "TablesUsed": [
+        "user.user"
+      ]
+    },
+    "skip_e2e": true
+  },
+  {
+    "comment": "Comments with subquery not merged into a single route",
+    "query": "select /* comment */ user.col from user where foo IN (select id from user where id > 1 and id < 10)",
+    "plan": {
+      "Type": "Complex",
+      "QueryType": "SELECT",
+      "Original": "select /* comment */ user.col from user where foo IN (select id from user where id > 1 and id < 10)",
+      "Instructions": {
+        "OperatorType": "UncorrelatedSubquery",
+        "Variant": "PulloutIn",
+        "PulloutVars": [
+          "__sq_has_values",
+          "__sq1"
+        ],
+        "Inputs": [
+          {
+            "InputName": "SubQuery",
+            "OperatorType": "Route",
+            "Variant": "Scatter",
+            "Keyspace": {
+              "Name": "user",
+              "Sharded": true
+            },
+            "FieldQuery": "select id from `user` where 1 != 1",
+            "Query": "select /* comment */ id from `user` where id > 1 and id < 10"
+          },
+          {
+            "InputName": "Outer",
+            "OperatorType": "Route",
+            "Variant": "Scatter",
+            "Keyspace": {
+              "Name": "user",
+              "Sharded": true
+            },
+            "FieldQuery": "select `user`.col from `user` where 1 != 1",
+            "Query": "select /* comment */ `user`.col from `user` where :__sq_has_values and foo in ::__sq1"
+          }
+        ]
+      },
+      "TablesUsed": [
+        "user.user"
+      ]
+    },
+    "skip_e2e": true
+  },
   {
     "comment": "for update",
     "query": "select user.col from user join user_extra for update",