sql: use custom boolean coercion logic in condition evaluation

erizocosmico · erizocosmico · commit ee455f09064a · 2019-06-24T15:03:08.000+02:00
Signed-off-by: Miguel Molina &lt;miguel@erizocosmi.co&gt;
diff --git a/engine_test.go b/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) {
diff --git a/sql/core.go b/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 +220,39 @@ 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:
+		if b != 0 {
+			return true, nil
+		}
+		return false, nil
+	case time.Duration:
+		if int64(b) != 0 {
+			return true, nil
+		}
+		return false, nil
+	case time.Time:
+		if b.UnixNano() != 0 {
+			return true, nil
+		}
+		return false, nil
+	case float32, float64:
+		if int(math.Round(v.(float64))) != 0 {
+			return true, nil
+		}
+		return false, nil
+	default:
+		return false, nil
+	}
+}
diff --git a/sql/plan/filter.go b/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
 		}
 	}

Original file line number	Diff line number	Diff line change
`@@ -107,12 +107,12 @@ func (i *FilterIter) Next() (sql.Row, error) {`
`107`	`107`	`return nil, err`
`108`	`108`	`}`
`109`	`109`
`110`		`- result, err := i.cond.Eval(i.ctx, row)`
	`110`	`+ ok, err := sql.EvaluateCondition(i.ctx, i.cond, row)`
`111`	`111`	`if err != nil {`
`112`	`112`	`return nil, err`
`113`	`113`	`}`
`114`	`114`
`115`		`- if result == true {`
	`115`	`+ if ok {`
`116`	`116`	`return row, nil`
`117`	`117`	`}`
`118`	`118`	`}`