tidb util 源码
tidb util 代码
文件路径：/parser/mysql/util.go
// Copyright 2015 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,
// See the License for the specific language governing permissions and
// limitations under the License.
package mysql
type lengthAndDecimal struct {
length int
decimal int
}
// defaultLengthAndDecimal provides default flen and decimal for fields
// from CREATE TABLE when they are unspecified.
var defaultLengthAndDecimal = map[byte]lengthAndDecimal{
TypeBit: {1, 0},
TypeTiny: {4, 0},
TypeShort: {6, 0},
TypeInt24: {9, 0},
TypeLong: {11, 0},
TypeLonglong: {20, 0},
TypeDouble: {22, -1},
TypeFloat: {12, -1},
TypeNewDecimal: {10, 0},
TypeDuration: {10, 0},
TypeDate: {10, 0},
TypeTimestamp: {19, 0},
TypeDatetime: {19, 0},
TypeYear: {4, 0},
TypeString: {1, 0},
TypeVarchar: {5, 0},
TypeVarString: {5, 0},
TypeTinyBlob: {255, 0},
TypeBlob: {65535, 0},
TypeMediumBlob: {16777215, 0},
TypeLongBlob: {4294967295, 0},
TypeJSON: {4294967295, 0},
TypeNull: {0, 0},
TypeSet: {-1, 0},
TypeEnum: {-1, 0},
}
// IsIntegerType indicate whether tp is an integer type.
func IsIntegerType(tp byte) bool {
switch tp {
case TypeTiny, TypeShort, TypeInt24, TypeLong, TypeLonglong:
return true
}
return false
}
// GetDefaultFieldLengthAndDecimal returns the default display length (flen) and decimal length for column.
// Call this when no flen assigned in ddl.
// or column value is calculated from an expression.
// For example: "select count(*) from t;", the column type is int64 and flen in ResultField will be 21.
// See https://dev.mysql.com/doc/refman/5.7/en/storage-requirements.html
func GetDefaultFieldLengthAndDecimal(tp byte) (flen int, decimal int) {
val, ok := defaultLengthAndDecimal[tp]
if ok {
return val.length, val.decimal
}
return -1, -1
}
// defaultLengthAndDecimal provides default flen and decimal for fields
// from CAST when they are unspecified.
var defaultLengthAndDecimalForCast = map[byte]lengthAndDecimal{
TypeString: {0, -1}, // flen & decimal differs.
TypeDate: {10, 0},
TypeDatetime: {19, 0},
TypeNewDecimal: {10, 0},
TypeDuration: {10, 0},
TypeLonglong: {22, 0},
TypeDouble: {22, -1},
TypeFloat: {12, -1},
TypeJSON: {4194304, 0}, // flen differs.
}
// GetDefaultFieldLengthAndDecimalForCast returns the default display length (flen) and decimal length for casted column
// when flen or decimal is not specified.
func GetDefaultFieldLengthAndDecimalForCast(tp byte) (flen int, decimal int) {
val, ok := defaultLengthAndDecimalForCast[tp]
if ok {
return val.length, val.decimal
}
return -1, -1
}
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