tidb collation 源码
tidb collation 代码
文件路径：/expression/collation.go
// Copyright 2020 PingCAP, 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 expression
import (
"github.com/pingcap/tidb/parser/ast"
"github.com/pingcap/tidb/parser/charset"
"github.com/pingcap/tidb/parser/mysql"
"github.com/pingcap/tidb/sessionctx"
"github.com/pingcap/tidb/types"
"github.com/pingcap/tidb/util/chunk"
"github.com/pingcap/tidb/util/collate"
"github.com/pingcap/tidb/util/hack"
"github.com/pingcap/tidb/util/logutil"
)
// ExprCollation is a struct that store the collation related information.
type ExprCollation struct {
Coer Coercibility
Repe Repertoire
Charset string
Collation string
}
type collationInfo struct {
coer Coercibility
coerInit bool
repertoire Repertoire
charset string
collation string
}
func (c *collationInfo) HasCoercibility() bool {
return c.coerInit
}
func (c *collationInfo) Coercibility() Coercibility {
return c.coer
}
// SetCoercibility implements CollationInfo SetCoercibility interface.
func (c *collationInfo) SetCoercibility(val Coercibility) {
c.coer = val
c.coerInit = true
}
func (c *collationInfo) Repertoire() Repertoire {
return c.repertoire
}
func (c *collationInfo) SetRepertoire(r Repertoire) {
c.repertoire = r
}
func (c *collationInfo) SetCharsetAndCollation(chs, coll string) {
c.charset, c.collation = chs, coll
}
func (c *collationInfo) CharsetAndCollation() (string, string) {
return c.charset, c.collation
}
// CollationInfo contains all interfaces about dealing with collation.
type CollationInfo interface {
// HasCoercibility returns if the Coercibility value is initialized.
HasCoercibility() bool
// Coercibility returns the coercibility value which is used to check collations.
Coercibility() Coercibility
// SetCoercibility sets a specified coercibility for this expression.
SetCoercibility(val Coercibility)
// Repertoire returns the repertoire value which is used to check collations.
Repertoire() Repertoire
// SetRepertoire sets a specified repertoire for this expression.
SetRepertoire(r Repertoire)
// CharsetAndCollation gets charset and collation.
CharsetAndCollation() (string, string)
// SetCharsetAndCollation sets charset and collation.
SetCharsetAndCollation(chs, coll string)
}
// Coercibility values are used to check whether the collation of one item can be coerced to
// the collation of other. See https://dev.mysql.com/doc/refman/8.0/en/charset-collation-coercibility.html
type Coercibility int
const (
// CoercibilityExplicit is derived from an explicit COLLATE clause.
CoercibilityExplicit Coercibility = 0
// CoercibilityNone is derived from the concatenation of two strings with different collations.
CoercibilityNone Coercibility = 1
// CoercibilityImplicit is derived from a column or a stored routine parameter or local variable or cast() function.
CoercibilityImplicit Coercibility = 2
// CoercibilitySysconst is derived from a “system constant” (the string returned by functions such as USER() or VERSION()).
CoercibilitySysconst Coercibility = 3
// CoercibilityCoercible is derived from a literal.
CoercibilityCoercible Coercibility = 4
// CoercibilityNumeric is derived from a numeric or temporal value.
CoercibilityNumeric Coercibility = 5
// CoercibilityIgnorable is derived from NULL or an expression that is derived from NULL.
CoercibilityIgnorable Coercibility = 6
)
var (
// CollationStrictnessGroup group collation by strictness
CollationStrictnessGroup = map[string]int{
"utf8_general_ci": 1,
"utf8mb4_general_ci": 1,
"utf8_unicode_ci": 2,
"utf8mb4_unicode_ci": 2,
charset.CollationASCII: 3,
charset.CollationLatin1: 3,
charset.CollationUTF8: 3,
charset.CollationUTF8MB4: 3,
charset.CollationBin: 4,
}
// CollationStrictness indicates the strictness of comparison of the collation. The unequal order in a weak collation also holds in a strict collation.
// For example, if a != b in a weak collation(e.g. general_ci), then there must be a != b in a strict collation(e.g. _bin).
// collation group id in value is stricter than collation group id in key
CollationStrictness = map[int][]int{
1: {3, 4},
2: {3, 4},
3: {4},
4: {},
}
)
// The Repertoire of a character set is the collection of characters in the set.
// See https://dev.mysql.com/doc/refman/8.0/en/charset-repertoire.html.
// Only String expression has Repertoire, for non-string expression, it does not matter what the value it is.
type Repertoire int
const (
// ASCII is pure ASCII U+0000..U+007F.
ASCII Repertoire = 0x01
// EXTENDED is extended characters: U+0080..U+FFFF
EXTENDED = ASCII << 1
// UNICODE is ASCII | EXTENDED
UNICODE = ASCII | EXTENDED
)
func deriveCoercibilityForScalarFunc(sf *ScalarFunction) Coercibility {
panic("this function should never be called")
}
func deriveCoercibilityForConstant(c *Constant) Coercibility {
if c.Value.IsNull() {
return CoercibilityIgnorable
} else if c.RetType.EvalType() != types.ETString {
return CoercibilityNumeric
}
return CoercibilityCoercible
}
func deriveCoercibilityForColumn(c *Column) Coercibility {
// For specified type null, it should return CoercibilityIgnorable, which means it got the lowest priority in DeriveCollationFromExprs.
if c.RetType.GetType() == mysql.TypeNull {
return CoercibilityIgnorable
}
switch c.RetType.EvalType() {
case types.ETJson:
case types.ETString:
return CoercibilityImplicit
default:
return CoercibilityNumeric
}
return CoercibilityImplicit
}
func deriveCollation(ctx sessionctx.Context, funcName string, args []Expression, retType types.EvalType, argTps ...types.EvalType) (ec *ExprCollation, err error) {
switch funcName {
case ast.Concat, ast.ConcatWS, ast.Lower, ast.Lcase, ast.Reverse, ast.Upper, ast.Ucase, ast.Quote, ast.Coalesce, ast.Greatest, ast.Least:
return CheckAndDeriveCollationFromExprs(ctx, funcName, retType, args...)
case ast.Left, ast.Right, ast.Repeat, ast.Trim, ast.LTrim, ast.RTrim, ast.Substr, ast.SubstringIndex, ast.Replace, ast.Substring, ast.Mid, ast.Translate:
return CheckAndDeriveCollationFromExprs(ctx, funcName, retType, args[0])
case ast.InsertFunc:
return CheckAndDeriveCollationFromExprs(ctx, funcName, retType, args[0], args[3])
case ast.Lpad, ast.Rpad:
return CheckAndDeriveCollationFromExprs(ctx, funcName, retType, args[0], args[2])
case ast.Elt, ast.ExportSet, ast.MakeSet:
return CheckAndDeriveCollationFromExprs(ctx, funcName, retType, args[1:]...)
case ast.FindInSet, ast.Regexp:
return CheckAndDeriveCollationFromExprs(ctx, funcName, types.ETInt, args...)
case ast.Field:
if argTps[0] == types.ETString {
return CheckAndDeriveCollationFromExprs(ctx, funcName, retType, args...)
}
case ast.RegexpReplace:
return CheckAndDeriveCollationFromExprs(ctx, funcName, retType, args[0], args[1], args[2])
case ast.Locate, ast.Instr, ast.Position, ast.RegexpLike, ast.RegexpSubstr, ast.RegexpInStr:
return CheckAndDeriveCollationFromExprs(ctx, funcName, retType, args[0], args[1])
case ast.GE, ast.LE, ast.GT, ast.LT, ast.EQ, ast.NE, ast.NullEQ, ast.Strcmp:
// if compare type is string, we should determine which collation should be used.
if argTps[0] == types.ETString {
ec, err = CheckAndDeriveCollationFromExprs(ctx, funcName, types.ETInt, args...)
if err != nil {
return nil, err
}
ec.Coer = CoercibilityNumeric
ec.Repe = ASCII
return ec, nil
}
case ast.If:
return CheckAndDeriveCollationFromExprs(ctx, funcName, retType, args[1], args[2])
case ast.Ifnull:
return CheckAndDeriveCollationFromExprs(ctx, funcName, retType, args[0], args[1])
case ast.Like:
ec, err = CheckAndDeriveCollationFromExprs(ctx, funcName, types.ETInt, args[0], args[1])
if err != nil {
return nil, err
}
ec.Coer = CoercibilityNumeric
ec.Repe = ASCII
return ec, nil
case ast.In:
if args[0].GetType().EvalType() == types.ETString {
return CheckAndDeriveCollationFromExprs(ctx, funcName, types.ETInt, args...)
}
case ast.DateFormat, ast.TimeFormat:
charsetInfo, collation := ctx.GetSessionVars().GetCharsetInfo()
return &ExprCollation{args[1].Coercibility(), args[1].Repertoire(), charsetInfo, collation}, nil
case ast.Cast:
// We assume all the cast are implicit.
ec = &ExprCollation{args[0].Coercibility(), args[0].Repertoire(), args[0].GetType().GetCharset(), args[0].GetType().GetCollate()}
// Non-string type cast to string type should use @@character_set_connection and @@collation_connection.
// String type cast to string type should keep its original charset and collation. It should not happen.
if retType == types.ETString && argTps[0] != types.ETString {
ec.Charset, ec.Collation = ctx.GetSessionVars().GetCharsetInfo()
}
return ec, nil
case ast.Case:
// FIXME: case function aggregate collation is not correct.
// We should only aggregate the `then expression`,
// case ... when ... expression will be rewritten to:
// args: eq scalar func(args: value, condition1), result1,
// eq scalar func(args: value, condition2), result2,
// ...
// else clause
// Or
// args: condition1, result1,
// condition2, result2,
// ...
// else clause
// so, arguments with odd index are the `then expression`.
if argTps[1] == types.ETString {
fieldArgs := make([]Expression, 0)
for i := 1; i < len(args); i += 2 {
fieldArgs = append(fieldArgs, args[i])
}
if len(args)%2 == 1 {
fieldArgs = append(fieldArgs, args[len(args)-1])
}
return CheckAndDeriveCollationFromExprs(ctx, funcName, retType, fieldArgs...)
}
case ast.Database, ast.User, ast.CurrentUser, ast.Version, ast.CurrentRole, ast.TiDBVersion:
chs, coll := charset.GetDefaultCharsetAndCollate()
return &ExprCollation{CoercibilitySysconst, UNICODE, chs, coll}, nil
case ast.Format, ast.Space, ast.ToBase64, ast.UUID, ast.Hex, ast.MD5, ast.SHA, ast.SHA2, ast.SM3:
// should return ASCII repertoire, MySQL's doc says it depends on character_set_connection, but it not true from its source code.
ec = &ExprCollation{Coer: CoercibilityCoercible, Repe: ASCII}
ec.Charset, ec.Collation = ctx.GetSessionVars().GetCharsetInfo()
return ec, nil
case ast.JSONPretty, ast.JSONQuote:
// JSON function always return utf8mb4 and utf8mb4_bin.
ec = &ExprCollation{Coer: CoercibilityCoercible, Repe: UNICODE, Charset: charset.CharsetUTF8MB4, Collation: charset.CollationUTF8MB4}
return ec, nil
}
ec = &ExprCollation{CoercibilityNumeric, ASCII, charset.CharsetBin, charset.CollationBin}
if retType == types.ETString {
ec.Charset, ec.Collation = ctx.GetSessionVars().GetCharsetInfo()
ec.Coer = CoercibilityCoercible
if ec.Charset != charset.CharsetASCII {
ec.Repe = UNICODE
}
}
return ec, nil
}
// DeriveCollationFromExprs derives collation information from these expressions.
// Deprecated, use CheckAndDeriveCollationFromExprs instead.
// TODO: remove this function after the all usage is replaced by CheckAndDeriveCollationFromExprs
func DeriveCollationFromExprs(ctx sessionctx.Context, exprs ...Expression) (dstCharset, dstCollation string) {
collation := inferCollation(exprs...)
return collation.Charset, collation.Collation
}
// CheckAndDeriveCollationFromExprs derives collation information from these expressions, return error if derives collation error.
func CheckAndDeriveCollationFromExprs(ctx sessionctx.Context, funcName string, evalType types.EvalType, args ...Expression) (et *ExprCollation, err error) {
ec := inferCollation(args...)
if ec == nil {
return nil, illegalMixCollationErr(funcName, args)
}
if evalType != types.ETString && ec.Coer == CoercibilityNone {
return nil, illegalMixCollationErr(funcName, args)
}
if evalType == types.ETString && ec.Coer == CoercibilityNumeric {
ec.Charset, ec.Collation = ctx.GetSessionVars().GetCharsetInfo()
ec.Coer = CoercibilityCoercible
ec.Repe = ASCII
}
if !safeConvert(ctx, ec, args...) {
return nil, illegalMixCollationErr(funcName, args)
}
return ec, nil
}
func safeConvert(ctx sessionctx.Context, ec *ExprCollation, args ...Expression) bool {
enc := charset.FindEncodingTakeUTF8AsNoop(ec.Charset)
for _, arg := range args {
if arg.GetType().GetCharset() == ec.Charset {
continue
}
// If value has ASCII repertoire, or it is binary string, just skip it.
if arg.Repertoire() == ASCII || types.IsBinaryStr(arg.GetType()) {
continue
}
if c, ok := arg.(*Constant); ok {
str, isNull, err := c.EvalString(ctx, chunk.Row{})
if err != nil {
return false
}
if isNull {
continue
}
if !enc.IsValid(hack.Slice(str)) {
return false
}
} else {
if arg.GetType().GetCollate() != charset.CharsetBin && ec.Charset != charset.CharsetBin && !isUnicodeCollation(ec.Charset) {
return false
}
}
}
return true
}
// inferCollation infers collation, charset, coercibility and check the legitimacy.
func inferCollation(exprs ...Expression) *ExprCollation {
if len(exprs) == 0 {
// TODO: see if any function with no arguments could run here.
dstCharset, dstCollation := charset.GetDefaultCharsetAndCollate()
return &ExprCollation{
Coer: CoercibilityIgnorable,
Repe: UNICODE,
Charset: dstCharset,
Collation: dstCollation,
}
}
repertoire := exprs[0].Repertoire()
coercibility := exprs[0].Coercibility()
dstCharset, dstCollation := exprs[0].GetType().GetCharset(), exprs[0].GetType().GetCollate()
if exprs[0].GetType().EvalType() == types.ETJson {
dstCharset, dstCollation = charset.CharsetUTF8MB4, charset.CollationUTF8MB4
}
unknownCS := false
// Aggregate arguments one by one, agg(a, b, c) := agg(agg(a, b), c).
for _, arg := range exprs[1:] {
argCharset, argCollation := arg.GetType().GetCharset(), arg.GetType().GetCollate()
// The collation of JSON is always utf8mb4_bin in builtin-func which is same as MySQL
// see details https://github.com/pingcap/tidb/issues/31320#issuecomment-1010599311
if arg.GetType().EvalType() == types.ETJson {
argCharset, argCollation = charset.CharsetUTF8MB4, charset.CollationUTF8MB4
}
// If one of the arguments is binary charset, we allow it can be used with other charsets.
// If they have the same coercibility, let the binary charset one to be the winner because binary has more precedence.
if dstCollation == charset.CollationBin || argCollation == charset.CollationBin {
if coercibility > arg.Coercibility() || (coercibility == arg.Coercibility() && argCollation == charset.CollationBin) {
coercibility, dstCharset, dstCollation = arg.Coercibility(), argCharset, argCollation
}
repertoire |= arg.Repertoire()
continue
}
// If charset is different, only if conversion without data loss is allowed:
// 1. ASCII repertoire is always convertible.
// 2. Non-Unicode charset can convert to Unicode charset.
// 3. utf8 can convert to utf8mb4.
// 4. constant value is allowed because we can eval and convert it directly.
// If we can not aggregate these two collations, we will get CoercibilityNone and wait for an explicit COLLATE clause, if
// there is no explicit COLLATE clause, we will get an error.
if dstCharset != argCharset {
switch {
case coercibility < arg.Coercibility():
if arg.Repertoire() == ASCII || arg.Coercibility() >= CoercibilitySysconst || isUnicodeCollation(dstCharset) {
repertoire |= arg.Repertoire()
continue
}
case coercibility == arg.Coercibility():
if (isUnicodeCollation(dstCharset) && !isUnicodeCollation(argCharset)) || (dstCharset == charset.CharsetUTF8MB4 && argCharset == charset.CharsetUTF8) {
repertoire |= arg.Repertoire()
continue
} else if (isUnicodeCollation(argCharset) && !isUnicodeCollation(dstCharset)) || (argCharset == charset.CharsetUTF8MB4 && dstCharset == charset.CharsetUTF8) {
coercibility, dstCharset, dstCollation = arg.Coercibility(), argCharset, argCollation
repertoire |= arg.Repertoire()
continue
} else if repertoire == ASCII && arg.Repertoire() != ASCII {
coercibility, dstCharset, dstCollation = arg.Coercibility(), argCharset, argCollation
repertoire |= arg.Repertoire()
continue
} else if repertoire != ASCII && arg.Repertoire() == ASCII {
repertoire |= arg.Repertoire()
continue
}
case coercibility > arg.Coercibility():
if repertoire == ASCII || coercibility >= CoercibilitySysconst || isUnicodeCollation(argCharset) {
coercibility, dstCharset, dstCollation = arg.Coercibility(), argCharset, argCollation
repertoire |= arg.Repertoire()
continue
}
}
// Cannot apply conversion.
repertoire |= arg.Repertoire()
coercibility, dstCharset, dstCollation = CoercibilityNone, charset.CharsetBin, charset.CollationBin
unknownCS = true
} else {
// If charset is the same, use lower coercibility, if coercibility is the same and none of them are _bin,
// derive to CoercibilityNone and _bin collation.
switch {
case coercibility == arg.Coercibility():
if dstCollation == argCollation {
} else if coercibility == CoercibilityExplicit {
return nil
} else if isBinCollation(dstCollation) {
} else if isBinCollation(argCollation) {
coercibility, dstCharset, dstCollation = arg.Coercibility(), argCharset, argCollation
} else {
coercibility, dstCharset, dstCollation = CoercibilityNone, argCharset, getBinCollation(argCharset)
}
case coercibility > arg.Coercibility():
coercibility, dstCharset, dstCollation = arg.Coercibility(), argCharset, argCollation
}
repertoire |= arg.Repertoire()
}
}
if unknownCS && coercibility != CoercibilityExplicit {
return nil
}
return &ExprCollation{
Coer: coercibility,
Repe: repertoire,
Charset: dstCharset,
Collation: dstCollation,
}
}
func isUnicodeCollation(ch string) bool {
return ch == charset.CharsetUTF8 || ch == charset.CharsetUTF8MB4
}
func isBinCollation(collate string) bool {
return collate == charset.CollationASCII || collate == charset.CollationLatin1 ||
collate == charset.CollationUTF8 || collate == charset.CollationUTF8MB4 ||
collate == charset.CollationGBKBin
}
// getBinCollation get binary collation by charset
func getBinCollation(cs string) string {
switch cs {
case charset.CharsetUTF8:
return charset.CollationUTF8
case charset.CharsetUTF8MB4:
return charset.CollationUTF8MB4
case charset.CharsetGBK:
return charset.CollationGBKBin
}
logutil.BgLogger().Error("unexpected charset " + cs)
// it must return something, never reachable
return charset.CollationUTF8MB4
}
var (
coerString = []string{"EXPLICIT", "NONE", "IMPLICIT", "SYSCONST", "COERCIBLE", "NUMERIC", "IGNORABLE"}
)
func illegalMixCollationErr(funcName string, args []Expression) error {
funcName = GetDisplayName(funcName)
switch len(args) {
case 2:
return collate.ErrIllegalMix2Collation.GenWithStackByArgs(args[0].GetType().GetCollate(), coerString[args[0].Coercibility()], args[1].GetType().GetCollate(), coerString[args[1].Coercibility()], funcName)
case 3:
return collate.ErrIllegalMix3Collation.GenWithStackByArgs(args[0].GetType().GetCollate(), coerString[args[0].Coercibility()], args[1].GetType().GetCollate(), coerString[args[1].Coercibility()], args[2].GetType().GetCollate(), coerString[args[2].Coercibility()], funcName)
default:
return collate.ErrIllegalMixCollation.GenWithStackByArgs(funcName)
}
}
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