use go-mysql-server condition evaluation logic

Signed-off-by: Miguel Molina <[email protected]>

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 - Panic on query using EXPLODE ([#755](https://github.com/src-d/go-mysql-server/issues/755))
 - Fixed error iterating over non ready repositories ([src-d/go-borges#54](https://github.com/src-d/go-borges/pull/54))
+- Error saying value could not be converted to bool.
 
 ## [0.22.0-rc1] - 2019-06-21
 
@@ -24,10 +25,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
-- function: correctly transform up explode nodes ([#757](https://github.com/src-d/go-mysql-server/pull/757)) 
+- function: correctly transform up explode nodes ([#757](https://github.com/src-d/go-mysql-server/pull/757))
 - git libraries bare or non bare format is automatically detected ([#897](https://github.com/src-d/gitbase/pull/897))
 - Fix bug that created multiple object cache with incorrect size ([#898](https://github.com/src-d/gitbase/pull/898))
-- sql/expression: handle null values in arithmetic expressions ([#760](https://github.com/src-d/go-mysql-server/pull/760)) 
+- sql/expression: handle null values in arithmetic expressions ([#760](https://github.com/src-d/go-mysql-server/pull/760))
 
 ## [0.22.0-beta1] - 2019-06-20
 
@@ -43,7 +44,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
-- function: correctly transform up explode nodes ([#757](https://github.com/src-d/go-mysql-server/pull/757)) 
+- function: correctly transform up explode nodes ([#757](https://github.com/src-d/go-mysql-server/pull/757))
 
 ## [0.21.0] - 2019-06-20
 

integration_test.go

@@ -496,6 +496,19 @@ func TestIntegration(t *testing.T) {
 				{"lordran.local", int64(1)},
 			},
 		},
+		{
+			`
+			SELECT file_path
+			FROM commit_files
+			NATURAL JOIN refs
+			WHERE ref_name = 'HEAD'
+			AND LANGUAGE(file_path) = 'Go';
+			`,
+			[]sql.Row{
+				{"go/example.go"},
+				{"vendor/foo.go"},
+			},
+		},
 	}
 
 	var pid uint64

squash_iterator.go

@@ -3486,17 +3486,7 @@ func (i *squashCommitFileBlobsIter) Close() error {
 }
 
 func evalFilters(ctx *sql.Context, row sql.Row, filters sql.Expression) (bool, error) {
-	v, err := filters.Eval(ctx, row)
-	if err != nil {
-		return false, err
-	}
-
-	v, err = sql.Boolean.Convert(v)
-	if err != nil {
-		return false, err
-	}
-
-	return v.(bool), nil
+	return sql.EvaluateCondition(ctx, filters, row)
 }
 
 var errInvalidCommit = errors.NewKind("invalid commit of type: %T")