CN108363806A - Multi-version concurrency control method, device, server and the storage medium of database - Google Patents
Multi-version concurrency control method, device, server and the storage medium of database Download PDFInfo
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Abstract
The present invention discloses a kind of multi-version concurrency control method of database, device, server and storage medium, this method：When Current transaction starts, the transaction number of the Current transaction is blocked by exclusive lock mode；If the current operation of the Current transaction is write operation, affairs savepoint is generated；Target data page corresponding with the write operation is searched, and locks the target data page in a manner of exclusive lock；The current operation is executed according to default rule.Pass through this lock-out facility so that the record quantity that the quantity of lock is changed with affairs can be significantly reduced lock quantity without direct relation, reduce lock conflict and block resource consumption, improve the concurrent efficiency of data base management system.
Description
Technical field
The present invention relates to database technical field more particularly to a kind of multi-version concurrency control method of database, device,
Server and storage medium.
Background technology
Multi version concurrency control (Multi-Version Concurrency Control, MVCC) can ensure data one
Under the premise of cause property, the read and write access performance of high concurrent is provided, is a kind of important technical for promoting database concurrency performance.
Current each mainstream data library management system all realizes MVCC mechanism substantially, but the MVCC realization mechanisms of each product exist obviously
Difference.For example, PostgreSQL and SQL Server, which are based on physical record, realizes MVCC, multiple versions are directly preserved in systems
Physical record；And Oracle, InnoDB and be based on rollback record up to dream database (DM7) and realize MVCC, system only preserves most
The physical record of new version records the historical information for preserving data using rollback.
It is recorded based on rollback and realizes that the basic ideas of MVCC are：Judge whether current record meets consistency when reading record
Whether conditions dictate, that is, usually said data are returned as it can be seen that if current record is invisible using previous version is directed toward
The pointer of rolling record recalls historical data, and the ultimately constructed consistency that meets reads desired data.Oracle is by modification record
Transaction number, affairs submit the SCN (System Change Number) generated and rollback recording address to be stored in data page head
ITL (Interest Transaction List) in, for judging record visibility and the visible colophon of construction.
The transaction number of modification record and rollback recording address are stored in (DM7 in the two systems field of record by InnoDB and DM7 respectively
The two fields are respectively defined as TID (Transaction Identity) and UPA (Undo Page Address), inside
A global active transaction chained list is maintained in depositing, and an active transaction view is maintained in transaction structure.
MVCC eliminates data reading and writing conflict, and read operation will not block write operation, and write operation will not block read operation.
While one user changes a line record, other users still can correctly read effective edition data of this line record.
But it is concurrent write, write operation, still can cause conflict, row grade lock be commonly used to solution write, write conflict.In traditional concept, one
Before a affairs TrxA modifications data line, need that exclusive row grade is locked (X locks) in the row data one, if another thing
Business TrxB has first blocked this row data, then the system of blocking can block Current transaction TrxA, until TrxB discharges this row grade
Lock.Using this row grade locking methods, data line is often changed, is required for generating one row grade lock, if an affairs modification
A large amount of records will accordingly generate a large amount of row grade lock.These locks can consume a large amount of memory source, and with lock object
Increase, safeguards that the HASH tables collision probability of these locks can also increase therewith, and then influence the concurrency performance of system.The row of InnoDB
Whether grade block uses above-mentioned basic ideas, according to the SQL statement type of execution, Transaction service and can utilize
The factors such as index, using different locking methods.
In order to reduce the resource consumption of lock object, each database product all takes series of optimum means, such as
InnoDB using a position (BIT) come indicate a line on some specific data page record, relative to directly use line identifier
(ROWID) it is indicated, the resource of lock object consumption can be greatly decreased.But over all, the block expense and thing of affairs
The record number positive correlation of business modification, cannot really reduce the resource consumption of lock object.
Invention content
The present invention provides a kind of multi-version concurrency control method of database, device, server and storage medium, reduces lock
Quantity, reduce lock conflict and block resource consumption, improve the concurrent efficiency of data base management system.
In a first aspect, an embodiment of the present invention provides a kind of multi-version concurrency control methods of database, including：
When Current transaction starts, the transaction number of the Current transaction is blocked by exclusive lock mode；
If the current operation of the Current transaction is write operation, affairs savepoint is generated；
Target data page corresponding with the write operation is searched, and locks the target data page in a manner of exclusive lock；
The current operation is executed according to default rule.
Further, after being blocked to the transaction number of the Current transaction by exclusive lock mode, further include：
If the transaction isolation grade of the Current transaction is serialization or repeatable read, collection activity transaction view and divide
The maximum transaction number matched；
If the transaction isolation grade of the Current transaction is to read to submit, after generating affairs savepoint, the work is collected
Dynamic transaction view and the allocated maximum transaction number.
Further, described that the current operation, packet are executed according to default rule if the current operation is to be inserted into
It includes：
Be inserted into the target data page and be inserted into data, by the write-in of the transaction number of the Current transaction with it is described to be inserted
Enter the TID field of the corresponding record of data, and discharges the lock of the target data page.
Further, described that the current behaviour is executed according to default rule if the current operation is to delete or update
Make, including：
Read the transaction number in the TID field of record to be operated in the target data page；
Sentenced according to transaction number, the active transaction view and the allocated maximum transaction number in the TID field
Visibility of the disconnected record to be operated to the Current transaction；
The current operation is executed to the visibility of the Current transaction according to the record to be operated.
Further, described that the current behaviour is executed to the visibility of the Current transaction according to the record to be operated
Make, including：
If the record to be operated to the Current transaction as it can be seen that delete or update the data in the target data page,
The transaction number of the Current transaction is written to the TID field of the record to be operated, and discharges the lock of the target data page；
If the record to be operated is invisible to the Current transaction, the lock of the target data page is discharged, and to institute
The transaction number stated in TID field is blocked in a manner of exclusive lock, when the corresponding affairs of transaction number in the TID field are submitted
Or when rollback, the transaction number in the TID field is blocked successfully, re-executes and searches target data page, lock onto target data
The step of page and judgement record visibility；If it is described it is to be operated record to the Current transaction as it can be seen that if execute the current behaviour
Make, discharges the lock of the target data page；If the record to be operated is invisible to the Current transaction, according to described current
The transaction isolation grade of affairs executes corresponding operation.
Further, described that corresponding operation is executed according to the transaction isolation grade of the Current transaction, including：
If the transaction isolation grade of the Current transaction is to read to submit, the Current transaction is rolled back into the affairs and is preserved
Point；
If the transaction isolation grade of the Current transaction is serialization or repeatable read, it is determined that the current operation failure,
And export error information.
Further, after having executed all operations of the Current transaction, the transaction number of the Current transaction is discharged
Lock.
Second aspect, the embodiment of the present invention additionally provide a kind of Multi version concurrency control device of database, the device packet
It includes：
Transaction number lockout module is used for when Current transaction starts, by exclusive lock mode to the thing of the Current transaction
Business number is blocked；
Savepoint generation module generates affairs savepoint if the current operation for the Current transaction is write operation；
Data page locking module for searching target data page corresponding with the write operation, and is locked in a manner of exclusive lock
The fixed target data page；
Operation executing module, for executing the current operation according to default rule.
The third aspect, the embodiment of the present invention additionally provide a kind of server, and the server includes：
One or more processors；
Storage device, for storing one or more programs；
When one or more of programs are executed by one or more of processors so that one or more of processing
Device realizes the multi-version concurrency control method of the database as described in any embodiment of the present invention.
Fourth aspect, the embodiment of the present invention additionally provide a kind of a kind of computer readable storage medium of server, deposit thereon
Computer program is contained, more editions that the database as described in any embodiment of the present invention is realized when which is executed by processor
This concurrency control method.
The present invention provides a kind of multi-version concurrency control method of database, when Current transaction starts, passes through exclusive lock
Mode blocks the transaction number of the Current transaction, prevents other affairs from being blocked again to Current transaction and changes number
According to.If the current operation of the Current transaction is write operation, affairs savepoint is generated, so as in the processing procedure of affairs,
It can be by rolling back to certain part operation of some affairs savepoint revocation to database；Search mesh corresponding with the write operation
Data page is marked, and locks the target data page in a manner of exclusive lock, it can be ensured that in data modification operation, other affairs are not
It can modify to same data；The behaviour of the affairs is executed after block Current transaction number and target data page according to default rule
Make.Pass through this lock-out facility so that the record quantity that the quantity of lock is changed with affairs can be significantly reduced without direct relation
Quantity and block resource consumption are locked, the concurrent efficiency of data base management system is improved.
Description of the drawings
Fig. 1 is a kind of flow chart of the multi-version concurrency control method of database in the embodiment of the present invention one.
Fig. 2 is a kind of flow chart of the multi-version concurrency control method of database in the embodiment of the present invention two.
Fig. 3 is the flow chart of the multi-version concurrency control method of another database in the embodiment of the present invention two.
Fig. 4 is a kind of structural schematic diagram of the Multi version concurrency control device of database in the embodiment of the present invention three.
Fig. 5 is a kind of structural schematic diagram of server in the embodiment of the present invention four.
Specific implementation mode
The present invention is described in further detail with reference to the accompanying drawings and examples.It is understood that this place is retouched
The specific embodiment stated is used only for explaining the present invention rather than limitation of the invention.It also should be noted that in order to just
Only the parts related to the present invention are shown in description, attached drawing rather than entire infrastructure.
Embodiment one
Fig. 1 is a kind of flow chart of the multi-version concurrency control method for database that the embodiment of the present invention one provides, this reality
The case where example is applicable to the Multi version concurrency control of database is applied, this method can be filled by the Multi version concurrency control of database
It sets to execute, specifically comprises the following steps：
S110, when Current transaction starts, the transaction number of the Current transaction is blocked by exclusive lock mode.
Wherein, affairs refer to accessing and may updating the data a program execution unit of various data item in library
(unit).If affairs encounter mistake and are cancelled or rollback, all SQL statements operation of affairs can be all eliminated, data
Library is restored to the state before affairs execute.Exclusive lock, also referred to as exclusive lock (Exclusive Locks, abbreviation X lock) write lock, are
A kind of basic lock type only allows T to read and change M, other any affairs if affairs T locks data object M plus X
All cannot any kind of lock be added to M again, the lock on T releases M.This guarantees other affairs T release M on lock it
Before cannot read and change again M.System can increase the incremental TID counters of an overall situation, can be with when each affairs start
Obtain a unique ID.It is block object with transaction number TID_A when affairs A starts, creates one and exclusive TID is locked, and
Hold affairs to terminate.Since transaction number has globally unique characteristic, TID locks when affairs start not will produce conflict, agree
Surely success can be blocked.Affairs are always maintained at this TID and lock, and are discharged when affairs submission or rollback.
If the current operation of S120, the Current transaction is write operation, affairs savepoint is generated.
Wherein, write operation includes：It is inserted into (INSERT), deletes (DELETE) or update (UPDATE) etc..Affairs savepoint
It is a logical point in business process, we, without the entire affairs that retract, can be to make to answer transaction rollback to this point
With program can encounter it is secondary mistake when rollback partial transaction label.
S130, target data page corresponding with the write operation is searched, and locks the target data in a manner of exclusive lock
Page.
Wherein, exclusive latch (LATCH) may be used to the locking of target data page, latch is that a kind of lightweight is other
Lock is the concurrent control mechanism that data store internal is used for data access to web page.Wherein, latch obtain and release speed quickly.Show
Example property finds the data page for being inserted into record if current operation is to be inserted into, i.e., after target data page, with exclusive
Latch mode lock onto target data page, can prevent this data page of other transactions access.
S140, the current operation is executed according to default rule.
Wherein, default rule refers to the strategy how preset current operation executes, illustratively, can basis
The visibility principle of affairs and different transaction isolation grades are default corresponding with executing insertion, deleting and updating operation accordingly
Strategy, to realize the database mechanisms of high concurrent efficiency and low consumption of resources.
Optionally, after having executed all operations of the Current transaction, the lock of the transaction number of the Current transaction is discharged,
Can reduce occupancy to system resource after release lock, the operating efficiency of other affairs can also be accelerated, realize high concurrent efficiency,
The database row grade lock-out facility of low consumption of resources.
The present invention is by providing a kind of multi-version concurrency control method of database, when Current transaction starts, by only
It accounts for lock mode to block the transaction number of the Current transaction, prevents other affairs from Current transaction is blocked and being changed again
Data.If the current operation of the Current transaction is write operation, affairs savepoint is generated, so as in the processing procedure of affairs
In, it can be by rolling back to certain part operation of some affairs savepoint revocation to database；It searches corresponding with the write operation
Target data page, and the target data page is locked in a manner of exclusive lock, it can be ensured that in data modification operation, other things
Business cannot modify to same data；The current operation is executed according to default rule, described in operation after the completion release
The lock of the transaction number of Current transaction.Pass through this lock-out facility so that the record quantity that the quantity of lock is changed with affairs is without direct
Relationship, only when there is update inconsistency just need carry out explicitly block (i.e. Current transaction number to the transaction number in TID field into
Row block), it can be significantly reduced capable grade lock quantity, lock conflict and block resource consumption is reduced, improve data base administration system
The concurrent efficiency of system.
Embodiment two
Fig. 2 is a kind of flow chart of the multi-version concurrency control method of database provided by Embodiment 2 of the present invention, this reality
It is to execute institute according to default rule in the case of being inserted into apply example and provide current operation on the basis of the various embodiments described above
The embodiment of current operation is stated, as shown in Fig. 2, this method specifically includes：
S210, when Current transaction starts, the transaction number of the Current transaction is blocked by exclusive lock mode.
If the current operation of S220, the Current transaction is write operation, affairs savepoint is generated.
S230, target data page corresponding with the write operation (insertion) is searched, and locks the mesh in a manner of exclusive lock
Mark data page.
S240, insertion is inserted into data in the target data page, the transaction number write-in by the Current transaction and institute
The TID field for being inserted into the corresponding record of data is stated, and discharges the lock of the target data page.
Wherein, when carrying out insertion operation, corresponding data are inserted into the target data page of locking, by Current transaction
Transaction number write-in is corresponding to be inserted into the TID field of record, after the lock for discharging the target data page.It is accessed every time in affairs
And when changing the record, affairs can read the TRX_ID in the upper TID field of record, and be judged according to the visibility principle of record
The record further carries out current operation to the visibility of Current transaction, realizes the Multi version concurrency control of data.
Fig. 3 is the flow chart of the multi-version concurrency control method of another database provided by Embodiment 2 of the present invention, can
Choosing, on the basis of the various embodiments described above, it is in the case of deleting or being newer, according to default rule to provide current operation
The embodiment of the current operation is executed, as shown in figure 3, this method specifically includes：
S310, when Current transaction starts, the transaction number of the Current transaction is blocked by exclusive lock mode.
If the current operation of S320, the Current transaction is write operation, affairs savepoint is generated.
It optionally, can be according to the transaction isolation grade of Current transaction, collection activity transaction view and allocated most major issue
Business number, for when executing deletion or update operation, judging visibility of the record to be operated to the Current transaction.Wherein, living
Dynamic transaction view includes active transaction and its corresponding transaction number TID, and allocated maximum transaction number refers in current collection
At the time of transaction number, system has been the maximum transaction number that affairs are assigned to.
If specifically, the transaction isolation grade of the Current transaction is serialization or repeatable read, passing through exclusive lock side
After formula blocks the transaction number of the Current transaction, collection activity transaction view and allocated maximum transaction number；If
The transaction isolation grade of the Current transaction is to read to submit, then after generating affairs savepoint, collects the active transaction view
With the allocated maximum transaction number.
S330, target data page corresponding with the write operation (delete or update) is searched, and is locked in a manner of exclusive lock
The target data page.
S340, the transaction number in the TID field of record to be operated in the target data page is read；According to the TID words
Transaction number, the active transaction view and the allocated maximum transaction number in section judge the record to be operated to described
The visibility of Current transaction.
Wherein, current operation is when deleting or updating, to read the transaction number in the TID field of record to be operated, Ke Yishi
TRX_ID, the affairs which modifies recently to coping with the record to be operated.That is user accesses a record
When, the transaction number in the TID field of the record is first read, further according to the transaction number in this TID field whether in the work being collected into
In dynamic transaction view and whether judge the record to Current transaction whether as it can be seen that just may be used more than allocated maximum transaction number
Further to execute current operation.
S350, the current operation is executed to the visibility of the Current transaction according to the record to be operated.
Optionally, the transaction number according in the TID field, the active transaction view and it is described it is allocated most
Big transaction number judges visibility of the record to be operated to the Current transaction, including：
If meeting one of following situations, it is determined that the record to be operated is invisible to the Current transaction：
Transaction number in the TID field is one of in the active transaction view；
Transaction number in the TID field is more than the allocated maximum transaction number.
I.e. when the transaction number TRX_ID in TID field is less than allocated maximum transaction number and not in active transaction view
When, it can be determined that record to be operated is visible Current transaction, remaining situation is invisible.It can't see due to affairs and do not carry
Hand over any modification of the affairs to same record, so, if same record to Current transaction as it can be seen that if illustrate to change this record
Other affairs certainly it is submitted.When being judged as visible, it may be determined that the affairs for changing this record to be operated recently exist
Current transaction is submitted before starting, therefore the record is visible.If the record to Current transaction as it can be seen that if illustrate to change
The affairs of this record are submitted, this record can be changed by Current transaction.If record is invisible to Current transaction,
Illustrate that other affairs are concurrently changing this record, Current transaction cannot modify to the record.
Optionally, in S350, if it is described it is to be operated record to the Current transaction as it can be seen that being deleted in the target data page
It removes or updates the data, the transaction number of the Current transaction is written to the TID field of the record to be operated, and discharge the target
The lock of data page.I.e. if as it can be seen that if can directly be deleted or be updated operation, and in the TID words of corresponding modification record
The transaction number of Current transaction is written in section, before the lock that Current transaction discharges target data page, other affairs are cannot be right
This record is modified.
Optionally, in S350, if the record to be operated is invisible to the Current transaction, the target data is discharged
The lock of page, and the transaction number in the TID field is blocked in a manner of exclusive lock, the transaction number in the TID field
When corresponding affairs submission or rollback, the transaction number in the TID field is blocked successfully, lookup target data is re-executed
The step of page, lock onto target data page and judgement record visibility；If it is described it is to be operated record to the Current transaction as it can be seen that if
The current operation is executed, the lock of the target data page is discharged；If the record to be operated is invisible to the Current transaction,
Corresponding operation is then executed according to the transaction isolation grade of the Current transaction.
It is i.e. if invisible, illustrate that Current transaction cannot directly execute current update or delete operation, Ke Yi at this time
After release is to the lock of target data page, the transaction number in TID field is blocked using exclusive lock.Due in TID field
Transaction number an exclusive lock, therefore lock conflict are generated when affairs start, the block of Current transaction can be blocked, at this time
Block can be waited for.When the corresponding affairs of transaction number in TID field are submitted or after rollback, block just can be at
Work(, will wake up Current transaction at this time can continue current operation.It re-executes and searches target data page, lock onto target number
The step of according to page and judging record visibility (i.e. S330 and S340) is said if it is determined that when record is visible to the Current transaction
The rollback of the affairs of this bright modification record can continue to execute deletion or update operation.
If it is determined that when record is still invisible to the Current transaction, the lock of the target data page is discharged, and according to
The transaction isolation grade of the Current transaction executes corresponding operation, specifically includes：
If the transaction isolation grade of the Current transaction is to read to submit, the Current transaction is rolled back into the affairs and is preserved
Point；
If the transaction isolation grade of the Current transaction is serialization or repeatable read, it is determined that the current operation failure,
And export error information.
Wherein, the corresponding affairs of transaction number are submitted in TID field, but record to be operated still can not to Current transaction
See, according to the definition for reading submission transaction isolation grade, the affairs savepoint can be rolled back to, the active transaction is collected again and regard
Figure and the allocated maximum transaction number re-execute deletion according to S330 to S350 or update operate.
The technical solution of the present embodiment provides a kind of multi-version concurrency control method of database, by being executed in affairs
When insertion, update or delete operation, transaction number is written to the TID field of record to be operated, it is primary hidden to treat operation note progress
The block of formula.After starting due to affairs, transaction number remains constant, no matter this affairs has modified how many row records, this
TID field value on a little records is all identical.Using the TID field and database door bolt on record, a kind of high concurrent effect is realized
Rate, low consumption of resources database row grade lock-out facility, solve the problems, such as to write, write concurrency conflict.In the feelings for not generating update inconsistency
Under condition, row grade lock is thoroughly eliminated, no matter an affairs have modified how many row records, not will produce capable grade lock object.Multiple
Transaction concurrency modification is recorded with a line, in the case of generating update inconsistency, reads the TID field of record, is carried out to the TID read
Block blocks transaction number by being converted into for the block of record row.Using this lock-out facility, the quantity and affairs of lock
The record quantity of modification just needs explicitly to be blocked without direct relation, only when there is update inconsistency, can greatly subtract
Quantity is locked less, is reduced lock conflict and block resource consumption, is improved the concurrent efficiency of data base management system.
Embodiment three
Fig. 4 show a kind of structural representation of the Multi version concurrency control device of database of the offer of the embodiment of the present invention three
The case where figure, the present embodiment is applicable to the Multi version concurrency control of database, as shown in figure 4, the multi version of the database is simultaneously
Control device is sent out, including：
Transaction number lockout module 410 is used for when Current transaction starts, by exclusive lock mode to the Current transaction
Transaction number is blocked；
Savepoint generation module 420 generates affairs preservation if the current operation for the Current transaction is write operation
Point；
Data page locking module 430, for searching target data page corresponding with the write operation, and in a manner of exclusive lock
Lock the target data page；
Operation executing module 440, for executing the current operation according to default rule.
Optionally, which further includes：
First affairs collection module, for carrying out blocking it to the transaction number of the Current transaction by exclusive lock mode
Afterwards, if the transaction isolation grade of the Current transaction is serialization or repeatable read, collection activity transaction view and allocated
Maximum transaction number；
Second affairs collection module is generating affairs if the transaction isolation grade for the Current transaction is to read to submit
After savepoint, the active transaction view and the allocated maximum transaction number are collected.
Optionally, the operation executing module 440 includes：
Transaction number reading unit reads in the target data page and waits for if being to delete or update for the current operation
Transaction number in the TID field of operation note；
Visibility judge unit, for according in the TID field transaction number, the active transaction view and it is described
The maximum transaction number of distribution judges visibility of the record to be operated to the Current transaction；
First operation execution unit, described in the visibility execution according to the record to be operated to the Current transaction
Current operation.
Optionally, first operation execution unit includes：
First operation executes subelement, if for the record to be operated to the Current transaction as it can be seen that in the target
It deletes or updates the data in data page, the transaction number of the Current transaction is written to the TID field of the record to be operated, and release
Put the lock of the target data page；
Second operation executes subelement, if invisible to the Current transaction for the record to be operated, discharges institute
The lock of target data page is stated, and the transaction number in the TID field is blocked in a manner of exclusive lock, when the TID field
In the corresponding affairs of transaction number submit or when rollback, the transaction number in the TID field blocked successfully, lookup is re-executed
The step of target data page, lock onto target data page and judgement record visibility；If the record to be operated is to the current thing
Business discharges the lock of the target data page as it can be seen that then execute the current operation；If the record to be operated is still worked as to described
Preceding affairs are invisible, then execute corresponding operation according to the transaction isolation grade of the Current transaction.
Optionally, the second operation executes subelement and is specifically used for：In the record to be operated still to the Current transaction
In the case of sightless, if the transaction isolation grade of the Current transaction is to read to submit, the Current transaction is rolled back to described
Affairs savepoint；If the transaction isolation grade of the Current transaction is serialization or repeatable read, it is determined that the current operation loses
It loses, and exports error information.
Optionally, operation executing module 440 includes：
Second operation execution unit is inserted into be inserted if being to be inserted into for the current operation in the target data page
Enter data, the write-in of the transaction number of the Current transaction is inserted into the TID field of the corresponding record of data with described, and discharge institute
State the lock of target data page.
Optionally, which further includes：Release module is locked, is used for after having executed all operations of the Current transaction,
Discharge the lock of the transaction number of the Current transaction.
Above-mentioned apparatus can perform the multi-version concurrency control method for the database that any embodiment of the present invention is provided, and have
Execute the corresponding function module of multi-version concurrency control method and advantageous effect of the database.
It is worth noting that, in the embodiment of the Multi version concurrency control device of above-mentioned database, included each mould
Block is only divided according to function logic, but is not limited to above-mentioned division, as long as corresponding function can be realized i.e.
It can；In addition, the specific name of each functional unit is also only to facilitate mutually distinguish, the protection model being not intended to restrict the invention
It encloses.
Example IV
The embodiment of the present invention provides a kind of server, which includes：One or more processors；Storage device is used
In the one or more programs of storage, when one or more of programs are executed by one or more of processors so that described
One or more processors realize the multi-version concurrency control method of the database described in any embodiment of the present invention.
Fig. 5 is the structural schematic diagram for the server that the embodiment of the present invention four provides, and referring to Fig. 5, which includes processing
Device 510 and memory 520；The quantity of processor 510 can be one or more in server, with a processor 510 in Fig. 5
For；Processor 510 in server can be connected with memory 520 by bus or other modes, to pass through bus in Fig. 5
For connection.
Memory 520 is used as a kind of computer readable storage medium, can be used for storing software program, computer can perform journey
Sequence and module, such as the corresponding program instruction of the multi-version concurrency control method of the database in the embodiment of the present invention/module (example
Such as, the transaction number lockout module 410 in the Multi version concurrency control device of database, savepoint generation module 420, data page lock
Cover half block 430 and operation executing module 440).Processor 510 is by running the software program being stored in memory 520, instruction
And module, the various function application to execute server and data processing, that is, realize the multi version of above-mentioned database
Concurrency control method.
Memory 520 can include mainly storing program area and storage data field, wherein storing program area can store operation system
Application program needed for system, at least one function；Storage data field can be stored uses created data etc. according to terminal.This
Outside, memory 520 may include high-speed random access memory, can also include nonvolatile memory, for example, at least one
Disk memory, flush memory device or other non-volatile solid state memory parts.In some instances, memory 520 can be into one
Step includes the memory remotely located relative to processor 510, these remote memories can pass through network connection to server.
The example of above-mentioned network includes but not limited to internet, intranet, LAN, mobile radio communication and combinations thereof.
Server provided in an embodiment of the present invention can not only execute and realize the data that any embodiment of the present invention provides
The multi-version concurrency control method in library can also execute other programs or method according to business specific requirement.
Embodiment five
The present embodiment provides a kind of computer readable storage mediums, are stored thereon with computer program, which is handled
The multi-version concurrency control method of the database described in any embodiment of the present invention is realized when device executes.
The computer program of computer-readable recording medium storage provided in this embodiment, it is real when in addition to being executed by processor
The multi-version concurrency control method of database described in existing any embodiment of the present invention can also include other programs, with reality
Now specific business demand.
By the description above with respect to embodiment, it is apparent to those skilled in the art that, the present invention
It can be realized by software and required common hardware, naturally it is also possible to which by hardware realization, but the former is more in many cases
Good embodiment.Based on this understanding, technical scheme of the present invention substantially in other words contributes to the prior art
Part can be expressed in the form of software products, which can be stored in computer readable storage medium
In, such as the floppy disk of computer, read-only memory (Read-Only Memory, ROM), random access memory (Random
Access Memory, RAM), flash memory (FLASH), hard disk or CD etc., including some instructions are with so that a computer is set
Standby (can be personal computer, server or the network equipment etc.) executes the method described in each embodiment of the present invention.
Note that above are only presently preferred embodiments of the present invention and institute's application technology principle.It will be appreciated by those skilled in the art that
The present invention is not limited to specific embodiments described here, can carry out for a person skilled in the art it is various it is apparent variation,
It readjusts and substitutes without departing from protection scope of the present invention.Therefore, although being carried out to the present invention by above example
It is described in further detail, but the present invention is not limited only to above example, without departing from the inventive concept, also
May include other more equivalent embodiments, and the scope of the present invention is determined by scope of the appended claims.
Claims (10)
1. a kind of multi-version concurrency control method of database, which is characterized in that including：
When Current transaction starts, the transaction number of the Current transaction is blocked by exclusive lock mode；
If the current operation of the Current transaction is write operation, affairs savepoint is generated；
Target data page corresponding with the write operation is searched, and locks the target data page in a manner of exclusive lock；
The current operation is executed according to default rule.
2. according to the method described in claim 1, it is characterized in that, in the affairs by exclusive lock mode to the Current transaction
After number being blocked, further include：
If the transaction isolation grade of the Current transaction is serialization or repeatable read, collection activity transaction view and allocated
Maximum transaction number；
If the transaction isolation grade of the Current transaction is to read to submit, after generating affairs savepoint, the activity thing is collected
Business view and the allocated maximum transaction number.
If 3. according to the method described in claim 1, it is characterized in that, the current operation be inserted into, it is described according to preset
Rule executes the current operation, including：
It is inserted into the target data page and is inserted into data, the transaction number write-in of the Current transaction is inserted into number with described
According to the TID field of corresponding record, and discharge the lock of the target data page.
4. if according to the method described in claim 2, it is characterized in that, the current operation is to delete or update, the basis
Default rule executes the current operation, including：
Read the transaction number in the TID field of record to be operated in the target data page；
Judge institute according to transaction number, the active transaction view and the allocated maximum transaction number in the TID field
State visibility of the record to be operated to the Current transaction；
The current operation is executed to the visibility of the Current transaction according to the record to be operated.
5. according to the method described in claim 4, it is characterized in that, it is described according to it is described it is to be operated record to the Current transaction
Visibility execute the current operation, including：
If the record to be operated is to the Current transaction as it can be seen that deleting or updating the data in the target data page, by institute
The TID field of the record to be operated is written in the transaction number for stating Current transaction, and discharges the lock of the target data page；
If the record to be operated is invisible to the Current transaction, the lock of the target data page is discharged, and to the TID
Transaction number in field is blocked in a manner of exclusive lock, when the corresponding affairs of transaction number in the TID field are submitted or returned
When rolling, the transaction number in the TID field is blocked successfully, re-execute search target data page, lock onto target data page and
The step of judging record visibility；If it is described it is to be operated record to the Current transaction as it can be seen that if execute the current operation, release
Put the lock of the target data page；If the record to be operated is invisible to the Current transaction, according to the Current transaction
Transaction isolation grade execute corresponding operation.
6. according to the method described in claim 5, it is characterized in that, described execute according to the transaction isolation grade of the Current transaction
Corresponding operation, including：
If the transaction isolation grade of the Current transaction is to read to submit, the Current transaction is rolled back into the affairs savepoint；
If the transaction isolation grade of the Current transaction is serialization or repeatable read, it is determined that the current operation failure, and it is defeated
Go out error information.
7. according to the method described in claim 1, it is characterized in that, further including：In all behaviour for having executed the Current transaction
After work, the lock of the transaction number of the Current transaction is discharged.
8. a kind of Multi version concurrency control device of database, which is characterized in that including：
Transaction number lockout module is used for when Current transaction starts, by exclusive lock mode to the transaction number of the Current transaction
It is blocked；
Savepoint generation module generates affairs savepoint if the current operation for the Current transaction is write operation；
Data page locking module for searching target data page corresponding with the write operation, and locks institute in a manner of exclusive lock
State target data page；
Operation executing module, for executing the current operation according to default rule.
9. a kind of server, which is characterized in that the server includes：
One or more processors；
Storage device, for storing one or more programs；
When one or more of programs are executed by one or more of processors so that one or more of processors are real
The now multi-version concurrency control method of the database as described in any in claim 1-7.
10. a kind of computer readable storage medium, is stored thereon with computer program, which is characterized in that the program is by processor
The multi-version concurrency control method of the database as described in any in claim 1-7 is realized when execution.
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