/
soundex.go
134 lines (117 loc) · 3.27 KB
/
soundex.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"
"unicode"
"github.com/dolthub/go-mysql-server/sql"
"github.com/dolthub/go-mysql-server/sql/expression"
"github.com/dolthub/go-mysql-server/sql/types"
)
// Soundex is a function that returns the soundex of a string. Two strings that
// sound almost the same should have identical soundex strings. A standard
// soundex string is four characters long, but the SOUNDEX() function returns
// an arbitrarily long string.
type Soundex struct {
expression.UnaryExpression
}
var _ sql.FunctionExpression = (*Soundex)(nil)
var _ sql.CollationCoercible = (*Soundex)(nil)
// NewSoundex creates a new Soundex expression.
func NewSoundex(e sql.Expression) sql.Expression {
return &Soundex{expression.UnaryExpression{Child: e}}
}
// FunctionName implements sql.FunctionExpression
func (s *Soundex) FunctionName() string {
return "soundex"
}
// Description implements sql.FunctionExpression
func (s *Soundex) Description() string {
return "returns the soundex of a string."
}
// Eval implements the Expression interface.
func (s *Soundex) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
v, err := s.Child.Eval(ctx, row)
if err != nil {
return nil, err
}
if v == nil {
return nil, nil
}
v, _, err = types.LongText.Convert(v)
if err != nil {
return nil, err
}
var b strings.Builder
var last rune
for _, c := range strings.ToUpper(v.(string)) {
if last == 0 && !unicode.IsLetter(c) {
continue
}
code := s.code(c)
if last == 0 {
b.WriteRune(c)
last = code
continue
}
if code == '0' || code == last {
continue
}
b.WriteRune(code)
last = code
}
if b.Len() == 0 {
return "0000", nil
}
for i := len([]rune(b.String())); i < 4; i++ {
b.WriteRune('0')
}
return b.String(), nil
}
func (s *Soundex) code(c rune) rune {
switch c {
case 'B', 'F', 'P', 'V':
return '1'
case 'C', 'G', 'J', 'K', 'Q', 'S', 'X', 'Z':
return '2'
case 'D', 'T':
return '3'
case 'L':
return '4'
case 'M', 'N':
return '5'
case 'R':
return '6'
}
return '0'
}
func (s *Soundex) String() string {
return fmt.Sprintf("%s(%s)", s.FunctionName(), s.Child)
}
// WithChildren implements the Expression interface.
func (s *Soundex) WithChildren(children ...sql.Expression) (sql.Expression, error) {
if len(children) != 1 {
return nil, sql.ErrInvalidChildrenNumber.New(s, len(children), 1)
}
return NewSoundex(children[0]), nil
}
// Type implements the Expression interface.
func (s *Soundex) Type() sql.Type {
return types.LongText
}
// CollationCoercibility implements the interface sql.CollationCoercible.
func (*Soundex) CollationCoercibility(ctx *sql.Context) (collation sql.CollationID, coercibility byte) {
return ctx.GetCollation(), 4
}