Merge pull request #1894 from pingcap/hanfei/product

*: add a flag to restrict cartesian product.

executor/executor_test.go

@@ -31,6 +31,7 @@ import (
 	"github.com/pingcap/tidb/kv"
 	"github.com/pingcap/tidb/model"
 	"github.com/pingcap/tidb/parser"
+	"github.com/pingcap/tidb/plan"
 	"github.com/pingcap/tidb/sessionctx/variable"
 	"github.com/pingcap/tidb/store/tikv"
 	"github.com/pingcap/tidb/util/testkit"
@@ -599,6 +600,15 @@ func (s *testSuite) TestJoin(c *C) {
 	result = tk.MustQuery("select a.c1 from t a , t1 b where a.c1 = b.c1 order by a.c1;")
 	result.Check(testkit.Rows("1", "2", "3", "4", "5", "6", "7"))
 
+	plan.AllowCartesianProduct = false
+	_, err := tk.Exec("select * from t, t1")
+	c.Check(plan.ErrCartesianProductUnsupported.Equal(err), IsTrue)
+	_, err = tk.Exec("select * from t left join t1 on 1")
+	c.Check(plan.ErrCartesianProductUnsupported.Equal(err), IsTrue)
+	_, err = tk.Exec("select * from t right join t1 on 1")
+	c.Check(plan.ErrCartesianProductUnsupported.Equal(err), IsTrue)
+	plan.AllowCartesianProduct = true
+
 }
 
 func (s *testSuite) TestMultiJoin(c *C) {

plan/optimizer.go

@@ -23,6 +23,9 @@ import (
 	"github.com/pingcap/tidb/terror"
 )
 
+// AllowCartesianProduct means whether tidb allows cartesian join without equal conditions.
+var AllowCartesianProduct = true
+
 // Optimize does optimization and creates a Plan.
 // The node must be prepared first.
 func Optimize(ctx context.Context, node ast.Node, is infoschema.InfoSchema) (Plan, error) {
@@ -49,6 +52,9 @@ func Optimize(ctx context.Context, node ast.Node, is infoschema.InfoSchema) (Pla
 		if err != nil {
 			return nil, errors.Trace(err)
 		}
+		if !AllowCartesianProduct && existsCartesianProduct(logic) {
+			return nil, ErrCartesianProductUnsupported
+		}
 		logic = EliminateProjection(logic)
 		info, err := logic.convert2PhysicalPlan(&requiredProperty{})
 		if err != nil {
@@ -60,6 +66,17 @@ func Optimize(ctx context.Context, node ast.Node, is infoschema.InfoSchema) (Pla
 	}
 	return p, nil
 }
+func existsCartesianProduct(p LogicalPlan) bool {
+	if join, ok := p.(*Join); ok && len(join.EqualConditions) == 0 {
+		return join.JoinType == InnerJoin || join.JoinType == LeftOuterJoin || join.JoinType == RightOuterJoin
+	}
+	for _, child := range p.GetChildren() {
+		if existsCartesianProduct(child.(LogicalPlan)) {
+			return true
+		}
+	}
+	return false
+}
 
 // PrepareStmt prepares a raw statement parsed from parser.
 // The statement must be prepared before it can be passed to optimize function.
@@ -86,12 +103,12 @@ const (
 
 // Optimizer base errors.
 var (
-	ErrOneColumn           = terror.ClassOptimizer.New(CodeOneColumn, "Operand should contain 1 column(s)")
-	ErrSameColumns         = terror.ClassOptimizer.New(CodeSameColumns, "Operands should contain same columns")
-	ErrMultiWildCard       = terror.ClassOptimizer.New(CodeMultiWildCard, "wildcard field exist more than once")
-	ErrUnSupported         = terror.ClassOptimizer.New(CodeUnsupported, "unsupported")
-	ErrInvalidGroupFuncUse = terror.ClassOptimizer.New(CodeInvalidGroupFuncUse, "Invalid use of group function")
-	ErrIllegalReference    = terror.ClassOptimizer.New(CodeIllegalReference, "Illegal reference")
+	ErrOneColumn                   = terror.ClassOptimizer.New(CodeOneColumn, "Operand should contain 1 column(s)")
+	ErrSameColumns                 = terror.ClassOptimizer.New(CodeSameColumns, "Operands should contain same columns")
+	ErrMultiWildCard               = terror.ClassOptimizer.New(CodeMultiWildCard, "wildcard field exist more than once")
+	ErrCartesianProductUnsupported = terror.ClassOptimizer.New(CodeUnsupported, "Cartesian product is unsupported")
+	ErrInvalidGroupFuncUse         = terror.ClassOptimizer.New(CodeInvalidGroupFuncUse, "Invalid use of group function")
+	ErrIllegalReference            = terror.ClassOptimizer.New(CodeIllegalReference, "Illegal reference")
 )
 
 func init() {

tidb-server/main.go

@@ -56,6 +56,7 @@ var (
 	reportStatus    = flag.Bool("report-status", true, "If enable status report HTTP service.")
 	logFile         = flag.String("log-file", "", "log file path")
 	joinCon         = flag.Int("join-concurrency", 5, "the number of goroutines that participate joining.")
+	crossJoin       = flag.Bool("cross-join", true, "whether support cartesian product or not.")
 	metricsAddr     = flag.String("metrics-addr", "", "prometheus pushgateway address, leaves it empty will disable prometheus push.")
 	metricsInterval = flag.Int("metrics-interval", 15, "prometheus client push interval in second, set \"0\" to disable prometheus push.")
 	binlogSocket    = flag.String("binlog-socket", "", "socket file to write binlog")
@@ -92,6 +93,7 @@ func main() {
 	if joinCon != nil && *joinCon > 0 {
 		plan.JoinConcurrency = *joinCon
 	}
+	plan.AllowCartesianProduct = *crossJoin
 	// Call this before setting log level to make sure that TiDB info could be printed.
 	printer.PrintTiDBInfo()
 	log.SetLevelByString(cfg.LogLevel)