tidb util 源码
tidb util 代码
文件路径：/sessiontxn/staleread/util.go
// Copyright 2022 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 staleread
import (
"time"
"github.com/pingcap/tidb/expression"
"github.com/pingcap/tidb/parser/ast"
"github.com/pingcap/tidb/parser/mysql"
"github.com/pingcap/tidb/sessionctx"
"github.com/pingcap/tidb/types"
"github.com/tikv/client-go/v2/oracle"
)
// CalculateAsOfTsExpr calculates the TsExpr of AsOfClause to get a StartTS.
func CalculateAsOfTsExpr(sctx sessionctx.Context, tsExpr ast.ExprNode) (uint64, error) {
tsVal, err := expression.EvalAstExpr(sctx, tsExpr)
if err != nil {
return 0, err
}
if tsVal.IsNull() {
return 0, errAsOf.FastGenWithCause("as of timestamp cannot be NULL")
}
toTypeTimestamp := types.NewFieldType(mysql.TypeTimestamp)
// We need at least the millionsecond here, so set fsp to 3.
toTypeTimestamp.SetDecimal(3)
tsTimestamp, err := tsVal.ConvertTo(sctx.GetSessionVars().StmtCtx, toTypeTimestamp)
if err != nil {
return 0, err
}
tsTime, err := tsTimestamp.GetMysqlTime().GoTime(sctx.GetSessionVars().Location())
if err != nil {
return 0, err
}
return oracle.GoTimeToTS(tsTime), nil
}
// CalculateTsWithReadStaleness calculates the TsExpr for readStaleness duration
func CalculateTsWithReadStaleness(sctx sessionctx.Context, readStaleness time.Duration) (uint64, error) {
nowVal, err := expression.GetStmtTimestamp(sctx)
if err != nil {
return 0, err
}
tsVal := nowVal.Add(readStaleness)
minTsVal := expression.GetMinSafeTime(sctx)
return oracle.GoTimeToTS(expression.CalAppropriateTime(tsVal, nowVal, minTsVal)), nil
}
// IsStmtStaleness indicates whether the current statement is staleness or not
func IsStmtStaleness(sctx sessionctx.Context) bool {
return sctx.GetSessionVars().StmtCtx.IsStaleness
}
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