/
is_tag.go
60 lines (48 loc) · 1.27 KB
/
is_tag.go
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package function
import (
"fmt"
"reflect"
"gopkg.in/src-d/go-git.v4/plumbing"
"github.com/src-d/go-mysql-server/sql"
"github.com/src-d/go-mysql-server/sql/expression"
)
// IsTag checks the given string is a tag name.
type IsTag struct {
expression.UnaryExpression
}
// NewIsTag creates a new IsTag function.
func NewIsTag(e sql.Expression) sql.Expression {
return &IsTag{expression.UnaryExpression{Child: e}}
}
// Eval implements the expression interface.
func (f *IsTag) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
span, ctx := ctx.Span("gitbase.IsTag")
defer span.Finish()
val, err := f.Child.Eval(ctx, row)
if err != nil {
return nil, err
}
if val == nil {
return false, nil
}
name, ok := val.(string)
if !ok {
return nil, sql.ErrInvalidType.New(reflect.TypeOf(val).String())
}
return plumbing.ReferenceName(name).IsTag(), nil
}
func (f IsTag) String() string {
return fmt.Sprintf("is_tag(%s)", f.Child)
}
// TransformUp implements the Expression interface.
func (f IsTag) TransformUp(fn sql.TransformExprFunc) (sql.Expression, error) {
child, err := f.Child.TransformUp(fn)
if err != nil {
return nil, err
}
return fn(NewIsTag(child))
}
// Type implements the Expression interface.
func (IsTag) Type() sql.Type {
return sql.Boolean
}