/
concat.go
112 lines (91 loc) · 2.65 KB
/
concat.go
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// Copyright 2020-2021 Dolthub, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package function
import (
"fmt"
"strings"
"github.com/dolthub/go-mysql-server/sql"
)
// Concat joins several strings together.
type Concat struct {
args []sql.Expression
}
var _ sql.FunctionExpression = (*Concat)(nil)
// NewConcat creates a new Concat UDF.
func NewConcat(args ...sql.Expression) (sql.Expression, error) {
if len(args) == 0 {
return nil, sql.ErrInvalidArgumentNumber.New("CONCAT", "1 or more", 0)
}
return &Concat{args}, nil
}
// FunctionName implements sql.FunctionExpression
func (c *Concat) FunctionName() string {
return "concat"
}
// Description implements sql.FunctionExpression
func (c *Concat) Description() string {
return "concatenates any group of fields into a single string."
}
// Type implements the Expression interface.
func (c *Concat) Type() sql.Type { return sql.LongText }
// IsNullable implements the Expression interface.
func (c *Concat) IsNullable() bool {
for _, arg := range c.args {
if arg.IsNullable() {
return true
}
}
return false
}
func (c *Concat) String() string {
var args = make([]string, len(c.args))
for i, arg := range c.args {
args[i] = arg.String()
}
return fmt.Sprintf("concat(%s)", strings.Join(args, ", "))
}
// WithChildren implements the Expression interface.
func (*Concat) WithChildren(children ...sql.Expression) (sql.Expression, error) {
return NewConcat(children...)
}
// Resolved implements the Expression interface.
func (c *Concat) Resolved() bool {
for _, arg := range c.args {
if !arg.Resolved() {
return false
}
}
return true
}
// Children implements the Expression interface.
func (c *Concat) Children() []sql.Expression { return c.args }
// Eval implements the Expression interface.
func (c *Concat) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
var parts []string
for _, arg := range c.args {
val, err := arg.Eval(ctx, row)
if err != nil {
return nil, err
}
if val == nil {
return nil, nil
}
val, err = sql.LongText.Convert(val)
if err != nil {
return nil, err
}
parts = append(parts, val.(string))
}
return strings.Join(parts, ""), nil
}