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like.go
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like.go
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package expression
import (
"bytes"
"fmt"
"regexp"
"strings"
"sync"
"github.com/src-d/go-mysql-server/internal/regex"
"github.com/src-d/go-mysql-server/sql"
)
// Like performs pattern matching against two strings.
type Like struct {
BinaryExpression
pool *sync.Pool
cached bool
}
// NewLike creates a new LIKE expression.
func NewLike(left, right sql.Expression) sql.Expression {
var cached = true
Inspect(right, func(e sql.Expression) bool {
if _, ok := e.(*GetField); ok {
cached = false
}
return true
})
return &Like{
BinaryExpression: BinaryExpression{left, right},
pool: nil,
cached: cached,
}
}
// Type implements the sql.Expression interface.
func (l *Like) Type() sql.Type { return sql.Boolean }
// Eval implements the sql.Expression interface.
func (l *Like) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
span, ctx := ctx.Span("expression.Like")
defer span.Finish()
left, err := l.Left.Eval(ctx, row)
if err != nil || left == nil {
return nil, err
}
left, err = sql.Text.Convert(left)
if err != nil {
return nil, err
}
var (
matcher regex.Matcher
disposer regex.Disposer
right string
)
// eval right and convert to text
if !l.cached || l.pool == nil {
var v interface{}
v, err = l.Right.Eval(ctx, row)
if err != nil || v == nil {
return nil, err
}
v, err = sql.Text.Convert(v)
if err != nil {
return nil, err
}
right = patternToRegex(v.(string))
}
// for non-cached regex every time create a new matcher
if !l.cached {
matcher, disposer, err = regex.New(regex.Default(), right)
} else {
if l.pool == nil {
l.pool = &sync.Pool{
New: func() interface{} {
r, _, e := regex.New(regex.Default(), right)
if e != nil {
err = e
return nil
}
return r
},
}
}
matcher = l.pool.Get().(regex.Matcher)
}
if matcher == nil {
return nil, err
}
ok := matcher.Match(left.(string))
if !l.cached {
disposer.Dispose()
} else if l.pool != nil {
l.pool.Put(matcher)
}
return ok, nil
}
func (l *Like) String() string {
return fmt.Sprintf("%s LIKE %s", l.Left, l.Right)
}
// WithChildren implements the Expression interface.
func (l *Like) WithChildren(children ...sql.Expression) (sql.Expression, error) {
if len(children) != 2 {
return nil, sql.ErrInvalidChildrenNumber.New(l, len(children), 2)
}
return NewLike(children[0], children[1]), nil
}
func patternToRegex(pattern string) string {
var buf bytes.Buffer
buf.WriteRune('^')
var escaped bool
for _, r := range strings.Replace(regexp.QuoteMeta(pattern), `\\`, `\`, -1) {
switch r {
case '_':
if escaped {
buf.WriteRune(r)
} else {
buf.WriteRune('.')
}
case '%':
if !escaped {
buf.WriteString(".*")
} else {
buf.WriteRune(r)
}
case '\\':
if escaped {
buf.WriteString(`\\`)
} else {
escaped = true
continue
}
default:
if escaped {
buf.WriteString(`\`)
}
buf.WriteRune(r)
}
if escaped {
escaped = false
}
}
buf.WriteRune('$')
return buf.String()
}