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concat_ws.go
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concat_ws.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/gabereiser/go-mysql-server/sql"
"github.com/gabereiser/go-mysql-server/sql/types"
)
// ConcatWithSeparator joins several strings together. The first argument is
// the separator for the rest of the arguments. The separator is added between
// the strings to be concatenated. The separator can be a string, as can the
// rest of the arguments. If the separator is NULL, the result is NULL.
type ConcatWithSeparator struct {
args []sql.Expression
}
var _ sql.FunctionExpression = (*ConcatWithSeparator)(nil)
// NewConcatWithSeparator creates a new NewConcatWithSeparator UDF.
func NewConcatWithSeparator(args ...sql.Expression) (sql.Expression, error) {
if len(args) == 0 {
return nil, sql.ErrInvalidArgumentNumber.New("CONCAT_WS", "1 or more", 0)
}
return &ConcatWithSeparator{args}, nil
}
// FunctionName implements sql.FunctionExpression
func (f *ConcatWithSeparator) FunctionName() string {
return "concat_ws"
}
// Description implements sql.FunctionExpression
func (f *ConcatWithSeparator) Description() string {
return "concatenates any group of fields into a single string. The first argument is the separator for the rest of the arguments. The separator is added between the strings to be concatenated. The separator can be a string, as can the rest of the arguments. If the separator is NULL, the result is NULL."
}
// Type implements the Expression interface.
func (f *ConcatWithSeparator) Type() sql.Type { return types.LongText }
// IsNullable implements the Expression interface.
func (f *ConcatWithSeparator) IsNullable() bool {
for _, arg := range f.args {
if arg.IsNullable() {
return true
}
}
return false
}
func (f *ConcatWithSeparator) String() string {
var args = make([]string, len(f.args))
for i, arg := range f.args {
args[i] = arg.String()
}
return fmt.Sprintf("%s(%s)", f.FunctionName(), strings.Join(args, ","))
}
// WithChildren implements the Expression interface.
func (*ConcatWithSeparator) WithChildren(children ...sql.Expression) (sql.Expression, error) {
return NewConcatWithSeparator(children...)
}
// Resolved implements the Expression interface.
func (f *ConcatWithSeparator) Resolved() bool {
for _, arg := range f.args {
if !arg.Resolved() {
return false
}
}
return true
}
// Children implements the Expression interface.
func (f *ConcatWithSeparator) Children() []sql.Expression { return f.args }
// Eval implements the Expression interface.
func (f *ConcatWithSeparator) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
var parts []string
for i, arg := range f.args {
val, err := arg.Eval(ctx, row)
if err != nil {
return nil, err
}
if val == nil && i == 0 {
return nil, nil
}
if val == nil {
continue
}
val, err = types.LongText.Convert(val)
if err != nil {
return nil, err
}
parts = append(parts, val.(string))
}
return strings.Join(parts[1:], parts[0]), nil
}