tidb keyflags 代码
文件路径：/kv/keyflags.go
/ Copyright 2021 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 kv
/ KeyFlags are metadata associated with key
type KeyFlags uint8
const (
flagPresumeKNE KeyFlags = 1 << iota
flagNeedLocked
/ The following are assertion related flags.
/ There are four choices of the two bits:
/ * 0: Assertion is not set and can be set later.
/ * flagAssertExists: We assert the key exists.
/ * flagAssertNotExists: We assert the key doesn't exist.
/ * flagAssertExists | flagAssertNotExists: Assertion cannot be made on this key (unknown).
/ Once either (or both) of the two flags is set, we say assertion is set (`HasAssertionFlags` becomes true), and
/ it's expected to be unchangeable within the current transaction.
flagAssertExists
flagAssertNotExists
/ the flag indicates the conflict and constraint check of the key should be postponed
/ to the next pessimistic lock or prewrite request.
flagNeedConstraintCheckInPrewrite
flagPreviousPresumeKNE
)
/ HasPresumeKeyNotExists returns whether the associated key use lazy check.
func (f KeyFlags) HasPresumeKeyNotExists() bool {
return f&flagPresumeKNE != 0
}
/ HasNeedLocked returns whether the key needed to be locked
func (f KeyFlags) HasNeedLocked() bool {
return f&flagNeedLocked != 0
}
/ HasAssertExists returns whether the key is asserted to already exist before the current transaction.
func (f KeyFlags) HasAssertExists() bool {
return f&flagAssertExists != 0 && f&flagAssertNotExists == 0
}
/ HasAssertNotExists returns whether the key is asserted not to exist before the current transaction.
func (f KeyFlags) HasAssertNotExists() bool {
return f&flagAssertNotExists != 0 && f&flagAssertExists == 0
}
/ HasAssertUnknown returns whether the key is unable to do any assertion.
func (f KeyFlags) HasAssertUnknown() bool {
return f&flagAssertExists != 0 && f&flagAssertNotExists != 0
}
/ HasAssertionFlags returns whether assertion is set on this key.
func (f KeyFlags) HasAssertionFlags() bool {
return f&flagAssertExists != 0 || f&flagAssertNotExists != 0
}
/ HasNeedConstraintCheckInPrewrite returns whether the key needs to do constraint and conflict check in prewrite.
func (f KeyFlags) HasNeedConstraintCheckInPrewrite() bool {
return f&flagNeedConstraintCheckInPrewrite != 0
}
/ FlagsOp describes KeyFlags modify operation.
type FlagsOp uint16
const (
/ SetPresumeKeyNotExists marks the existence of the associated key is checked lazily.
SetPresumeKeyNotExists FlagsOp = iota
/ SetNeedLocked marks the associated key need to be acquired lock.
SetNeedLocked
/ SetAssertExist marks the associated key must exist.
SetAssertExist
/ SetAssertNotExist marks the associated key must not exists.
SetAssertNotExist
/ SetAssertUnknown marks the associated key is unknown and can not apply other assertion.
SetAssertUnknown
/ SetAssertNone marks the associated key without any assert.
SetAssertNone
/ SetNeedConstraintCheckInPrewrite sets the flag flagNeedConstraintCheckInPrewrite
SetNeedConstraintCheckInPrewrite
/ SetPreviousPresumeKeyNotExists marks the PNE flag is set in previous statements, thus it cannot be unset when
/ retrying or rolling back a statement.
SetPreviousPresumeKeyNotExists
)
/ ApplyFlagsOps applys flagspos to origin.
func ApplyFlagsOps(origin KeyFlags, ops ...FlagsOp) KeyFlags {
for _, op := range ops {
switch op {
case SetPresumeKeyNotExists:
origin |= flagPresumeKNE
case SetNeedLocked:
origin |= flagNeedLocked
case SetAssertExist:
origin |= flagAssertExists
origin &= ^flagAssertNotExists
case SetAssertNotExist:
origin |= flagAssertNotExists
origin &= ^flagAssertExists
case SetAssertUnknown:
origin |= flagAssertExists
origin |= flagAssertNotExists
case SetNeedConstraintCheckInPrewrite:
origin |= flagNeedConstraintCheckInPrewrite
case SetPreviousPresumeKeyNotExists:
origin |= flagPreviousPresumeKNE
}
}
return origin
}