fix: derived table join column expression to be part of add join pred…

…icate on rewrite

Signed-off-by: Harshit Gangal <harshit@planetscale.com>

go/test/endtoend/vtgate/queries/derived/derived_test.go

@@ -113,3 +113,17 @@ func TestDerivedTablesWithLimit(t *testing.T) {
                 (SELECT id, user_id FROM music LIMIT 10) as m on u.id = m.user_id`,
 		`[[INT64(1) INT64(1)] [INT64(5) INT64(2)] [INT64(1) INT64(3)] [INT64(2) INT64(4)] [INT64(3) INT64(5)] [INT64(5) INT64(7)] [INT64(4) INT64(6)] [INT64(6) NULL]]`)
 }
+
+func TestDerivedTableColumnAliasWithJoin(t *testing.T) {
+	mcmp, closer := start(t)
+	defer closer()
+
+	mcmp.AssertMatches(`SELECT user.id FROM user join (SELECT id as uid FROM user) t on t.uid = user.id`,
+		`[[INT64(5)] [INT64(4)] [INT64(3)] [INT64(2)] [INT64(1)]]`)
+	mcmp.AssertMatches(`SELECT user.id FROM user left join (SELECT id as uid FROM user) t on t.uid = user.id`,
+		`[[INT64(5)] [INT64(4)] [INT64(3)] [INT64(2)] [INT64(1)]]`)
+	mcmp.AssertMatches(`SELECT user.id FROM user join (SELECT id FROM user) t(uid) on t.uid = user.id`,
+		`[[INT64(5)] [INT64(4)] [INT64(3)] [INT64(2)] [INT64(1)]]`)
+	mcmp.AssertMatches(`SELECT user.id FROM user left join (SELECT id FROM user) t(uid) on t.uid = user.id`,
+		`[[INT64(5)] [INT64(4)] [INT64(3)] [INT64(2)] [INT64(1)]]`)
+}

go/vt/vtgate/planbuilder/operators/apply_join.go

@@ -163,7 +163,9 @@ func (aj *ApplyJoin) AddJoinPredicate(ctx *plancontext.PlanningContext, expr sql
 		col := breakExpressionInLHSandRHSForApplyJoin(ctx, pred, TableID(aj.LHS))
 		aj.JoinPredicates.add(col)
 		ctx.AddJoinPredicates(pred, col.RHSExpr)
+		ctx.JoinPredInProgress = pred
 		rhs = rhs.AddPredicate(ctx, col.RHSExpr)
+		ctx.JoinPredInProgress = nil
 	}
 	aj.RHS = rhs
 }

go/vt/vtgate/planbuilder/operators/horizon.go

@@ -100,6 +100,9 @@ func (h *Horizon) AddPredicate(ctx *plancontext.PlanningContext, expr sqlparser.
 	}
 
 	newExpr := semantics.RewriteDerivedTableExpression(expr, tableInfo)
+	if ctx.JoinPredInProgress != nil {
+		ctx.AddJoinPredicates(ctx.JoinPredInProgress, newExpr)
+	}
 	if ContainsAggr(ctx, newExpr) {
 		return newFilter(h, expr)
 	}

go/vt/vtgate/planbuilder/operators/rewriters.go

@@ -218,6 +218,9 @@ func bottomUp(
 			childID = childID.Merge(resolveID(oldInputs[0]))
 		}
 		in, changed := bottomUp(operator, childID, resolveID, rewriter, shouldVisit, false)
+		if DebugOperatorTree && changed.Changed() {
+			fmt.Println(ToTree(in))
+		}
 		anythingChanged = anythingChanged.Merge(changed)
 		newInputs[i] = in
 	}

go/vt/vtgate/planbuilder/plancontext/planning_context.go

@@ -28,6 +28,7 @@ type PlanningContext struct {
 	SemTable     *semantics.SemTable
 	VSchema      VSchema
 
+	JoinPredInProgress sqlparser.Expr
 	// joinPredicates maps each original join predicate (key) to a slice of
 	// variations of the RHS predicates (value). This map is used to handle
 	// different scenarios in join planning, where the RHS predicates are

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

@@ -5221,5 +5221,27 @@
         "main.unsharded_a"
       ]
     }
+  },
+  {
+    "comment": "join with derived table with alias and join condition - merge into route",
+    "query": "select 1 from user join (select id as uid from user) as t where t.uid = user.id",
+    "plan": {
+      "QueryType": "SELECT",
+      "Original": "select 1 from user join (select id as uid from user) as t where t.uid = user.id",
+      "Instructions": {
+        "OperatorType": "Route",
+        "Variant": "Scatter",
+        "Keyspace": {
+          "Name": "user",
+          "Sharded": true
+        },
+        "FieldQuery": "select 1 from (select id as uid from `user` where 1 != 1) as t, `user` where 1 != 1",
+        "Query": "select 1 from (select id as uid from `user`) as t, `user` where t.uid = `user`.id",
+        "Table": "`user`"
+      },
+      "TablesUsed": [
+        "user.user"
+      ]
+    }
   }
 ]