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regexp_like.go
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regexp_like.go
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// Copyright 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"
"regexp"
"strings"
"sync"
"sync/atomic"
"gopkg.in/src-d/go-errors.v1"
"github.com/Rock-liyi/p2pdb-store/sql"
"github.com/Rock-liyi/p2pdb-store/sql/expression"
)
// RegexpLike implements the REGEXP_LIKE function.
// https://dev.mysql.com/doc/refman/8.0/en/regexp.html#function_regexp-like
type RegexpLike struct {
Text sql.Expression
Pattern sql.Expression
Flags sql.Expression
cachedVal atomic.Value
re *regexp.Regexp
compileOnce sync.Once
compileErr error
}
var _ sql.FunctionExpression = (*RegexpLike)(nil)
// NewRegexpLike creates a new RegexpLike expression.
func NewRegexpLike(args ...sql.Expression) (sql.Expression, error) {
var r *RegexpLike
switch len(args) {
case 3:
r = &RegexpLike{
Text: args[0],
Pattern: args[1],
Flags: args[2],
}
case 2:
r = &RegexpLike{
Text: args[0],
Pattern: args[1],
}
default:
return nil, sql.ErrInvalidArgumentNumber.New("regexp_like", "2 or 3", len(args))
}
return r, nil
}
// FunctionName implements sql.FunctionExpression
func (r *RegexpLike) FunctionName() string {
return "regexp_like"
}
// Description implements sql.FunctionExpression
func (r *RegexpLike) Description() string {
return "returns whether string matches regular expression."
}
// Type implements the sql.Expression interface.
func (r *RegexpLike) Type() sql.Type { return sql.Int8 }
// IsNullable implements the sql.Expression interface.
func (r *RegexpLike) IsNullable() bool { return true }
// Children implements the sql.Expression interface.
func (r *RegexpLike) Children() []sql.Expression {
var result = []sql.Expression{r.Text, r.Pattern}
if r.Flags != nil {
result = append(result, r.Flags)
}
return result
}
// Resolved implements the sql.Expression interface.
func (r *RegexpLike) Resolved() bool {
return r.Text.Resolved() && r.Pattern.Resolved() && (r.Flags == nil || r.Flags.Resolved())
}
// WithChildren implements the sql.Expression interface.
func (r *RegexpLike) WithChildren(children ...sql.Expression) (sql.Expression, error) {
required := 2
if r.Flags != nil {
required = 3
}
if len(children) != required {
return nil, sql.ErrInvalidChildrenNumber.New(r, len(children), required)
}
return NewRegexpLike(children...)
}
func (r *RegexpLike) String() string {
var args []string
for _, e := range r.Children() {
args = append(args, e.String())
}
return fmt.Sprintf("regexp_like(%s)", strings.Join(args, ", "))
}
func (r *RegexpLike) compile(ctx *sql.Context) {
r.compileOnce.Do(func() {
r.re, r.compileErr = compileRegex(ctx, r.Pattern, r.Flags, r.FunctionName(), nil)
})
}
// Eval implements the sql.Expression interface.
func (r *RegexpLike) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
span, ctx := ctx.Span("function.RegexpLike")
defer span.Finish()
cached := r.cachedVal.Load()
if cached != nil {
return cached, nil
}
r.compile(ctx)
if r.compileErr != nil {
return nil, r.compileErr
}
if r.re == nil {
return nil, nil
}
text, err := r.Text.Eval(ctx, row)
if err != nil {
return nil, err
}
if text == nil {
return nil, nil
}
text, err = sql.LongText.Convert(text)
if err != nil {
return nil, err
}
var outVal int8
if r.re.MatchString(text.(string)) {
outVal = int8(1)
} else {
outVal = int8(0)
}
if canBeCached(r.Text) {
r.cachedVal.Store(outVal)
}
return outVal, nil
}
func compileRegex(ctx *sql.Context, pattern, flags sql.Expression, funcName string, row sql.Row) (*regexp.Regexp, error) {
patternVal, err := pattern.Eval(ctx, row)
if err != nil {
return nil, err
}
if patternVal == nil {
return nil, nil
}
patternVal, err = sql.LongText.Convert(patternVal)
if err != nil {
return nil, err
}
// Empty regex, throw illegal argument
if len(patternVal.(string)) == 0 {
return nil, errors.NewKind("Illegal argument to regular expression.").New()
}
flagsStr := "(?i)"
if flags != nil {
f, err := flags.Eval(ctx, row)
if err != nil {
return nil, err
}
if f == nil {
return nil, nil
}
f, err = sql.LongText.Convert(f)
if err != nil {
return nil, err
}
flagsStr = f.(string)
flagsStr, err = consolidateRegexpFlags(flagsStr, funcName)
if err != nil {
return nil, err
}
flagsStr = fmt.Sprintf("(?%s)", flagsStr)
flagsStr = strings.Replace(flagsStr, "c", `\c`, -1)
}
return regexp.Compile(flagsStr + patternVal.(string))
}
// consolidateRegexpFlags consolidates regexp flags by removing duplicates, resolving order of conflicting flags, and
// verifying that all flags are valid.
func consolidateRegexpFlags(flags, funcName string) (string, error) {
flagSet := make(map[string]struct{})
// The flag 'u' is unsupported for now, as there isn't an equivalent flag in golang's regexp library
for _, flag := range flags {
switch flag {
case 'c':
if _, ok := flagSet["i"]; ok {
delete(flagSet, "i")
}
case 'i':
flagSet["i"] = struct{}{}
case 'm':
flagSet["m"] = struct{}{}
case 'n':
flagSet["s"] = struct{}{}
default:
return "", sql.ErrInvalidArgument.New(funcName)
}
}
flags = ""
for flag := range flagSet {
flags += flag
}
return flags, nil
}
func canBeCached(e sql.Expression) bool {
hasCols := false
sql.Inspect(e, func(e sql.Expression) bool {
switch e.(type) {
case *expression.GetField, *expression.UserVar, *expression.SystemVar, *expression.ProcedureParam:
hasCols = true
}
return true
})
return !hasCols
}