Merge pull request #768 from erizocosmico/fix/bool-coercion

sql: use custom boolean coercion logic in condition evaluation

Author: ajnavarro

engine_test.go

@@ -1230,6 +1230,10 @@ var queries = []struct {
 		`SELECT (NULL+1)`,
 		[]sql.Row{{nil}},
 	},
+	{
+		`SELECT * FROM mytable WHERE NULL AND i = 3`,
+		[]sql.Row{},
+	},
 }
 
 func TestQueries(t *testing.T) {

sql/core.go

@@ -3,6 +3,8 @@ package sql // import "github.com/src-d/go-mysql-server/sql"
 import (
 	"fmt"
 	"io"
+	"math"
+	"time"
 
 	"gopkg.in/src-d/go-errors.v1"
 )
@@ -218,3 +220,27 @@ type Lockable interface {
 	// available.
 	Unlock(ctx *Context, id uint32) error
 }
+
+// EvaluateCondition evaluates a condition, which is an expression whose value
+// will be coerced to boolean.
+func EvaluateCondition(ctx *Context, cond Expression, row Row) (bool, error) {
+	v, err := cond.Eval(ctx, row)
+	if err != nil {
+		return false, err
+	}
+
+	switch b := v.(type) {
+	case bool:
+		return b, nil
+	case int, int64, int32, int16, int8, uint, uint64, uint32, uint16, uint8:
+		return b != 0, nil
+	case time.Duration:
+		return int64(b) != 0, nil
+	case time.Time:
+		return b.UnixNano() != 0, nil
+	case float32, float64:
+		return int(math.Round(v.(float64))) != 0, nil
+	default:
+		return false, nil
+	}
+}

sql/plan/filter.go

@@ -107,12 +107,12 @@ func (i *FilterIter) Next() (sql.Row, error) {
 			return nil, err
 		}
 
-		result, err := i.cond.Eval(i.ctx, row)
+		ok, err := sql.EvaluateCondition(i.ctx, i.cond, row)
 		if err != nil {
 			return nil, err
 		}
 
-		if result == true {
+		if ok {
 			return row, nil
 		}
 	}

sql/type.go

@@ -616,25 +616,13 @@ func (t booleanT) Convert(v interface{}) (interface{}, error) {
 	case bool:
 		return b, nil
 	case int, int64, int32, int16, int8, uint, uint64, uint32, uint16, uint8:
-		if b != 0 {
-			return true, nil
-		}
-		return false, nil
+		return b != 0, nil
 	case time.Duration:
-		if int64(b) != 0 {
-			return true, nil
-		}
-		return false, nil
+		return int64(b) != 0, nil
 	case time.Time:
-		if b.UnixNano() != 0 {
-			return true, nil
-		}
-		return false, nil
+		return b.UnixNano() != 0, nil
 	case float32, float64:
-		if int(math.Round(v.(float64))) != 0 {
-			return true, nil
-		}
-		return false, nil
+		return int(math.Round(v.(float64))) != 0, nil
 	case string:
 		return false, fmt.Errorf("unable to cast string to bool")