[4.1-dev] fix: resolve comma-joined tables in nested explicit JOIN ON conditions

pkg/sql/plan/build_test.go

@@ -3275,3 +3275,11 @@ func TestReplaceCaptureDedupJoinDoesNotShuffle(t *testing.T) {
 
 	t.Fatal("expected REPLACE plan to contain a DEDUP JOIN with OldColCaptureList")
 }
+
+func TestCommaJoinWithExplicitJoin(t *testing.T) {
+	mock := NewMockOptimizer(false)
+	sqls := []string{
+		"select nation.n_name from nation, nation2 join region on nation2.r_regionkey = region.r_regionkey",
+	}
+	runTestShouldPass(mock, t, sqls, false, false)
+}

pkg/sql/plan/query_builder.go

@@ -5042,7 +5042,7 @@ func (builder *QueryBuilder) buildTable(stmt tree.TableExpr, ctx *BindContext, p
 		if tbl.Right == nil {
 			return builder.buildTable(tbl.Left, ctx, preNodeId, leftCtx)
 		}
-		return builder.buildJoinTable(tbl, ctx)
+		return builder.buildJoinTable(tbl, ctx, leftCtx)
 
 	case *tree.ApplyTableExpr:
 		_, ok := tbl.Right.(*tree.TableFunction)
@@ -5327,7 +5327,7 @@ func (builder *QueryBuilder) addBinding(nodeID int32, alias tree.AliasClause, ct
 	return nil
 }
 
-func (builder *QueryBuilder) buildJoinTable(tbl *tree.JoinTableExpr, ctx *BindContext) (int32, error) {
+func (builder *QueryBuilder) buildJoinTable(tbl *tree.JoinTableExpr, ctx *BindContext, extLeftCtx *BindContext) (int32, error) {
 	joinType := plan.Node_INNER
 
 	switch tbl.JoinType {
@@ -5375,6 +5375,43 @@ func (builder *QueryBuilder) buildJoinTable(tbl *tree.JoinTableExpr, ctx *BindCo
 		return 0, err
 	}
 
+	// Comma (CROSS) joins produce nested trees where the outer left context
+	// is not visible in the inner ON condition
+	// (e.g. FROM a, b JOIN c ON a.x = c.y). Temporarily add extLeftCtx
+	// bindings to ctx for the ON condition binding, then remove them so
+	// the outer mergeContexts doesn't see a duplicate.
+	var extBindingsRestore func()
+	if extLeftCtx != nil {
+		var addedTables []string
+		for _, binding := range extLeftCtx.bindings {
+			if _, ok := ctx.bindingByTable[binding.table]; !ok {
+				ctx.bindings = append(ctx.bindings, binding)
+				ctx.bindingByTag[binding.tag] = binding
+				ctx.bindingByTable[binding.table] = binding
+				addedTables = append(addedTables, binding.table)
+			}
+		}
+		var addedCols []string
+		for col, binding := range extLeftCtx.bindingByCol {
+			if _, ok := ctx.bindingByCol[col]; !ok {
+				ctx.bindingByCol[col] = binding
+				addedCols = append(addedCols, col)
+			}
+		}
+		extBindingsRestore = func() {
+			for _, table := range addedTables {
+				delete(ctx.bindingByTable, table)
+			}
+			for _, col := range addedCols {
+				delete(ctx.bindingByCol, col)
+			}
+			for _, binding := range extLeftCtx.bindings {
+				delete(ctx.bindingByTag, binding.tag)
+			}
+			ctx.bindings = ctx.bindings[:len(ctx.bindings)-len(addedTables)]
+		}
+	}
+
 	node := &plan.Node{
 		NodeType:     plan.Node_JOIN,
 		Children:     []int32{leftChildID, rightChildID},
@@ -5444,6 +5481,9 @@ func (builder *QueryBuilder) buildJoinTable(tbl *tree.JoinTableExpr, ctx *BindCo
 		}
 	}
 
+	if extBindingsRestore != nil {
+		extBindingsRestore()
+	}
 	return nodeID, nil
 }