expression: rewrite builtin function: INSERT #4414
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expression/builtin_string.go
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| bf.tp.Flen = mysql.MaxBlobWidth | ||
| SetBinFlagOrBinStr(args[0].GetType(), bf.tp) | ||
| SetBinFlagOrBinStr(args[3].GetType(), bf.tp) | ||
| var sig builtinFunc |
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move the definition of sig and err to line 2619.
expression/builtin_string.go
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| if err != nil { | ||
| return d, errors.Trace(err) | ||
| strLength := int64(len(str)) | ||
| if pos < 1 || pos > strLength { |
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this check can be moved to line 2654?
expression/builtin_string.go
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| runes := []rune(str) | ||
| runeLength := int64(len(runes)) | ||
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| if pos < 1 || pos > runeLength { |
| sig := &builtinInsertFuncSig{newBaseBuiltinFunc(args, ctx)} | ||
| bf := newBaseBuiltinFuncWithTp(args, ctx, tpString, tpString, tpInt, tpInt, tpString) | ||
| bf.tp.Flen = mysql.MaxBlobWidth | ||
| SetBinFlagOrBinStr(args[0].GetType(), bf.tp) |
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this is a bug fix: for INSERT(str,pos,len,newstr), if str is a binary string, we should treat it like a byte array, otherwise we should treat it like a code point array. see builtinInsertBinarySig and builtinInsertSig for more detail
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If we use args[0].GetType() after newBaseBuiltinFunc,
args[0] has already been wrapped with cast.
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when arg[0] is a binary string, it will not be wrapped with a cast.
btw, I think wrapped cast functions should guarantee the correct type inference, and every function should do its type inference based on its children, no matter what expression the children is
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@jackysp @breeswish PTAL |
| if length > runeLength-pos+1 || length < 0 { | ||
| return string(runes[0:pos-1]) + newstr, false, nil | ||
| } | ||
| return string(runes[0:pos-1]) + newstr + string(runes[pos+length-1:]), false, nil |
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package main
import "fmt"
import "time"
func main() {
str := ""
str1 := "aaaa"
str2 := "bbbb"
str3 := "cccc"
start := time.Now()
for i, round := 0, 1000000; i < round; i++ {
str = str1 + str2 + str3
}
fmt.Printf("%vns\n", time.Now().Sub(start).Nanoseconds())
fmt.Printf("%s\n", str)
start = time.Now()
for i, round := 0, 1000000; i < round; i++ {
str = fmt.Sprintf("%s%s%s", str1, str2, str3)
}
fmt.Printf("%vns\n", time.Now().Sub(start).Nanoseconds())
fmt.Printf("%s\n", str)
}$go build a.go
$./a
56394494ns
aaaabbbbcccc
279845006ns
aaaabbbbccccIt seems fmt.Sprintf() has less efficiency.
…n/expression/string/insert
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@jackysp PTAL |
to #4080