WO2018113534A1

WO2018113534A1 - Database deadlock processing method and apparatus, and database system

Info

Publication number: WO2018113534A1
Application number: PCT/CN2017/115191
Authority: WO
Inventors: 范孝剑; 张广舟; 林晓斌; 周正中
Original assignee: 阿里巴巴集团控股有限公司
Priority date: 2016-12-20
Filing date: 2017-12-08
Publication date: 2018-06-28
Also published as: CN108205464B; CN108205464A

Abstract

A database deadlock processing method and apparatus, and a database system. The method comprises: dividing a transaction into N sub-transactions executed in sequence (S110); creating a savepoint and recording same before each of the N sub-transactions is executed (S120); sequentially executing the N sub-transactions (S130); when a lock wait occurs in an nth sub-transaction of the N sub-transactions and a waiting time is greater than a first waiting time corresponding to the nth sub-transaction, rolling the transaction back to a rollback savepoint (S140), wherein the rollback savepoint is a savepoint created before the nth sub-transaction is executed; and continuing to execute sub-transactions in the N sub-transactions in sequence following the rollback savepoint (S150). By means of dividing a transaction into a plurality of sub-transactions and setting a savepoint before execution, after the occurrence of a lock wait in a sub-transaction therein exceeds a first waiting time corresponding to the sub-transaction, the sub-transaction is rolled back to the savepoint prior to the sub-transaction and continues to be executed, so that the execution efficiency of a transaction experiencing deadlock can be improved to some extent.

Description

Method, device and database system for processing database deadlock

The present application claims the priority of the Chinese Patent Application No. 201611183503.2, entitled "Processing Method, Apparatus and Database System for Database Deadlock", which is filed on December 20, 2016, the entire contents of which are incorporated herein by reference. In the application.

Technical field

The present application relates to the field of databases, and in particular, to a method, an apparatus, and a database system for processing a database deadlock.

Background technique

Database deadlocks are a common problem in databases. Generating a deadlock generally requires the following four necessary conditions:

(1) Mutually exclusive conditions: A resource can only be used by one process at a time.

(2) Request and hold conditions: When a process blocks due to requesting resources, it keeps the resources that have been acquired.

(3) Non-deprivation conditions: The resources that the process has obtained cannot be forcibly deprived until the end of use.

(4) Loop wait condition: A loop-waiting resource relationship between head and tail is formed between several processes.

The method of resolving a deadlock in an existing database is usually determined by the database to determine whether a deadlock occurs. If a deadlock is found, the entire transaction operation is rolled back, and the application retry or requires human intervention. If a transaction takes a long time to execute, then when a transaction is forced to roll back due to a deadlock in execution, the transaction needs to be executed from the beginning, which can take a lot of unnecessary time.

How to improve the execution efficiency of a transaction in which a deadlock occurs is a technical problem to be solved in the embodiments of the present application.

Summary of the invention

The purpose of the embodiments of the present application is to provide a method, an apparatus, and a database system for processing a database deadlock to improve the execution efficiency of a transaction in which a deadlock occurs.

To solve the above technical problem, the embodiment of the present application is implemented as follows:

In a first aspect, a method for processing a database deadlock is provided, the method comprising: dividing a transaction into N sub-transactions executed sequentially, wherein N is a positive integer greater than 1; each of the N sub-transactions Creating a savepoint before the transaction is executed; sequentially executing the N child transactions; when the nth child transaction of the N child transactions has a lock wait and the wait time is greater than the first wait time corresponding to the nth child transaction, the transaction is rolled back To roll back the savepoint, where n is a positive integer less than or equal to N, the rollback savepoint is a savepoint created before the execution of the nth child transaction; continue to execute the rollback in the N subtransactions Sub-transaction after the point.

In a second aspect, an apparatus for processing a database deadlock is provided, the apparatus comprising: a transaction division unit, an execution unit, a savepoint creation unit, and a transaction rollback unit, wherein the transaction division unit divides the transaction into sequentially executed N a sub-transaction, where N is a positive integer greater than one; the execution unit sequentially executes the N sub-transactions; the savepoint creation unit creates a savepoint before executing each of the N sub-transactions; when the N sub-transactions When the nth child transaction in the lock waits and the wait time is greater than the first wait time corresponding to the nth child transaction, the transaction rollback unit rolls back the transaction to the rollback savepoint, where n is less than or equal to N. a positive integer, the rollback savepoint is a savepoint created before the execution of the nth child transaction; the execution unit continues to execute the N sequentially after the transaction rollback unit rolls back the transaction to the rollback savepoint The child transaction in the child transaction after the rollback savepoint.

The above at least one technical solution adopted by the embodiment of the present application can achieve the following beneficial effects: by splitting a transaction into multiple sub-transactions and setting a save point before execution, the sub-transaction in which the lock transaction waits for more than the first corresponding to the sub-transaction After waiting for the time, roll back to the savepoint before the child transaction and continue execution, so that the execution efficiency of the deadlock transaction can be improved to some extent.

DRAWINGS

The drawings described herein are intended to provide a further understanding of the present application, and are intended to be a part of this application. In the drawing:

1 is a flowchart of a method for processing a database deadlock according to an embodiment of the present application;

2 is a flow chart of a specific processing method for database deadlock in an embodiment of the present application;

3 is a schematic structural diagram of an electronic device according to an embodiment of the present application;

4 is a schematic structural diagram of an apparatus for processing a database deadlock according to an embodiment of the present application;

FIG. 5 is a schematic structural diagram of an apparatus for processing a database deadlock according to another embodiment of the present application.

detailed description

The technical solutions of the present application will be clearly and completely described in the following with reference to the specific embodiments of the present application and the corresponding drawings. It is apparent that the described embodiments are only a part of the embodiments of the present application, and not all of them. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present application without departing from the inventive scope are the scope of the present application.

The technical solutions provided by the embodiments of the present application are described in detail below with reference to the accompanying drawings.

1 is a flow chart of a method for processing a database deadlock in an embodiment of the present application. The method of Figure 1 is processed by the data The device of the deadlock is executed. In practical applications, the device that handles database deadlocks may be a functional module of the database system. The method includes:

S110, dividing the transaction into N sub-transactions executed in sequence.

Where N is a positive integer greater than one.

Transaction is a program execution unit that accesses and possibly updates various data items in the database. A transaction consists of the entire operation performed between a begin transaction and an end transaction. For example, in a relational database, a transaction can be a Structured Query Language (SQL) statement, a set of SQL statements, or an entire program.

It should be understood that in the present application, the transaction includes a plurality of Insert, Update, or Delete SQL statements and other database manipulation statements involving database modification, which can be further divided into a plurality of sub-transactions.

For example, suppose the transaction consists of the following SQL statement:

Delete from table 1 where col1=”value1”;

Insert into table2 values(value1,value2,value3...);

Update table3 set col2=”value4” where col3=“value5”.

The transaction can be further divided into multiple sub-transactions.

For example, the transaction can be divided into sub-transaction 1 and sub-transaction 2, where

Subtransaction 1 is:

Delete from table 1 where col1=”value1”;

Insert into table2 values(value1,value2,value3...);

Subtransaction 2 is:

Update table3 set col2=”value4” where col3=“value5”.

For another example, the transaction can also be divided into a sub-transaction 1, a sub-transaction 2, and a sub-transaction 3, wherein

Subtransaction 1 is:

Delete from table 1 where col1=”value1”;

Subtransaction 2 is:

Insert into table2 values(value1,value2,value3...);

Subtransaction 3 is:

Update table3 set col2=”value4” where col3=“value5”.

In a specific application, the sub-transaction may be divided according to the number of SQL statements therein, or the number of records inserted, updated, or deleted may be sub-transactions according to the number of records required to be inserted (updated), updated (updated), or deleted (Delete). The sub-transaction is divided according to the pre-estimated execution time, and the application is not limited herein.

S120: Create a savepoint before each of the N sub-transactions is executed.

A savepoint is a logical point in a transaction process. By saving a point, the transaction can be rolled back to the state of the savepoint without having to roll back the entire transaction.

The way to create savepoints can be found in the prior art. For example, in an Oracle database, savepoints can be created with the savepoint savepoint_name command. Where savepoint_name represents the savepoint name.

S130. Perform the N sub-transactions in sequence.

S140. When a lock wait is performed on the nth sub-transaction of the N sub-transactions and the waiting time is greater than the first waiting time corresponding to the n-th sub-transaction, the pending transaction is rolled back to the rollback savepoint.

Where n is a positive integer less than or equal to N, and the rollback savepoint is a savepoint created before the execution of the nth child transaction.

It should be understood that the nth sub-transaction of the present application refers to the nth sub-transaction executed sequentially in the N sub-transactions.

S150. Continue to sequentially execute the sub-transactions of the N sub-transactions after the rollback savepoint.

In the embodiment of the present application, by splitting a transaction into multiple sub-transactions and setting a save point before execution, before the sub-transaction lock waits for more than the first wait time corresponding to the sub-transaction, before rolling back to the sub-transaction The save point continues to execute, which can improve the execution efficiency of the deadlock transaction to a certain extent.

In step S140, the rollback savepoint is a savepoint created before the execution of the nth child transaction. The selection of the rollback savepoint determines the number of child transactions that the transaction needs to roll back. Therefore, before step S140, the method may further include: determining the rollback savepoint.

Optionally, as an embodiment, determining the rollback savepoint may be implemented as: when the nth sub-transaction of the N sub-transactions has a lock wait for the i-th time and the waiting time is greater than the first corresponding to the n-th sub-transaction Waiting time, according to the number of sub-transactions s that need to be rolled back according to the i-th lock, determine the roll-back save point, the mapping relationship between s and i is preset, and both i and s are positive integers.

It should be understood that the mapping relationship between s and i is preset. For example, a mapping relationship table between s and i may be preset, or a functional relationship between s and i may be preset, and so on.

Specifically, for example, the mapping relationship between s and i can be as shown in Table 1:

Table 1:

锁等待次数Lock wait times	11	22	33	44	55
需要回滚的子事务个数Number of sub-transactions that need to be rolled back	11	22	33	55	88

Or, for example, a functional relationship between s and i may be specified as s=i.

Of course, it should be understood that the above-mentioned mapping relationship table and function relationship are only schematic, and in actual applications, they can be set according to actual conditions.

In addition, it should be understood that since the number of sub-transactions s that need to be rolled back may be greater than the number n of sub-transactions that have been currently executed, when s < n, it may be determined that s sub-transactions need to be rolled back; when s ≥ n To determine the need to roll back n child transactions. In other words, when s<n, it is determined that the first save point before the n-s+1th sub-transaction is the roll-back save point; or, when s≥n, the save point before the first sub-transaction is determined. Save the point for this rollback.

In this implementation manner, the number of sub-transactions that need to be rolled back is determined by the number of times the lock waits and the waiting time is greater than the first waiting time, and the save point of the rollback is determined, thereby avoiding the rollback. The child transaction is set too low to release the lock, or the transaction is rolled back due to too many child transaction settings being rolled back.

Of course, it should be understood that the foregoing implementation manner only shows a possible implementation manner, and in a specific application, the rollback savepoint may also be determined in other manners.

It should be understood that the first waiting time corresponding to the lock waiting of each of the N sub-transactions may be the same or different.

Optionally, the first waiting time may be set by a user of the database. The user can set a fixed value for the first waiting time, or set the first waiting time according to some configuration rule. Setting a first waiting time according to a parameter, for example, a data operation type according to the nth sub-transaction, a record number of data operations related to the n-th sub-transaction, a sequence number n of the n-th sub-transaction, and the nth At least one of the number of times the sub-transaction has a lock waiting, setting the first waiting time.

Alternatively, optionally, as another embodiment, the first waiting time is set according to a random number. Setting the first wait time by random number prevents all connection timeouts from being the same.

In the embodiment of the present application, by flexibly setting the first waiting time of the lock waiting of the sub-transaction, the user can interfere with the deadlock process and improve the execution efficiency of the database.

In the embodiment of the present application, by flexibly setting the first waiting time for the lock wait of the nth sub-transaction, the number of sub-transactions that are rolled back can be reduced to some extent on the premise that the lock is released after the sub-transaction is rolled back.

Optionally, as an embodiment, step S150 is specifically implemented as: after rolling back to the rollback savepoint and waiting for the second waiting time, continuing to sequentially execute the sub-sub-transactions of the N sub-transactions after the roll-back savepoint Transaction.

Alternatively, the second waiting time may be set by a user of the database. The user can set a fixed value for the second waiting time or set the second waiting time according to some configuration rule.

Alternatively, optionally, the second waiting time is determined according to the type of SQL involved in the transaction. For example, data The second wait time of the Data Definition Language (DDL) type can be set longer; the second wait time of the data manipulation language (DML) can be set shorter, and so on.

Alternatively, optionally, the second waiting time is set according to a random number. Setting the second wait time by random number prevents all connection timeouts from being the same.

In the embodiment of the present application, by waiting for the second waiting time after rolling back to the rollback savepoint, the transaction that holds the lock of the nth child transaction can be prevented to some extent without releasing the lock, thereby causing the nth child. The transaction continues to lock out, further improving the execution efficiency of the deadlocked transaction.

Optionally, as an embodiment, the method further includes: when the save point corresponding to each of the N sub-transactions is created, the save point is sequentially recorded; and the transaction is rolled back to the rollback save When you click, delete the record of the savepoint created after the rollback savepoint.

To delete a savepoint, refer to the existing technology. For example, in the Oracle database, the created savepoint can be deleted by the release savepoint command. The specific command format is as follows

Release savepoint savepoint_name;

Where savepoint_name represents the name of the savepoint created.

In addition, if the record of the savepoint is stored in a linked list or other data structure, the record of the savepoint created after the rollback savepoint is also deleted from the linked list or data structure.

In the embodiment of the present application, by deleting the record of the save point after the rollback save point, the device for processing the database deadlock can quickly locate the save point of the rollback in the subsequent operation of determining the save point of the rollback.

When the save point needs to be additionally recorded, optionally, the save points created by each of the N sub-transactions before execution may be stored in the linked list in order, wherein the roll-back save point is by searching The list is determined.

In the embodiment of the present application, searching for a rollback savepoint that needs to be rolled back through the linked list can improve the efficiency of finding a rollback savepoint, thereby further improving the execution efficiency of the transaction in which the deadlock occurs.

Alternatively, optionally, as another embodiment, each of the N sub-transactions is created by a savepoint created before the execution according to the sequence number of the savepoint and a predetermined rule, and the rollback savepoint is based on the back The serial number of the savepoint is determined by the predetermined rule.

It should be understood that the record of the savepoint is not required. For example, the naming rule of the savepoint can be agreed to as the identifier name + sequence number. When it is determined that the sequence number of the savepoint is rolled back, the name of the savepoint can be determined to be rolled back, thereby finding the savepoint.

Of course, it should be understood that in practical applications, it is possible to record only the information of the save point, and not the number of sub-transactions that are rolled back. However, since each sub-transaction has a corresponding savepoint before it, determine the child that needs to be rolled back. The transaction is equivalent to determining the save point of the rollback.

Hereinafter, the embodiment shown in FIG. 1 of the present application will be further described in conjunction with specific embodiments.

2 is a flow chart of a specific processing method for database deadlock in an embodiment of the present application. In the scenario shown in FIG. 2, the transaction can be divided into three sub-transactions: sub-transaction 1, sub-transaction 2, and sub-transaction 3. The execution order is performed in the order of sub-transaction 1, sub-transaction 2, and sub-transaction 3. As shown in FIG. 2, before the sub-transaction 1 is executed, the savepoint savepoint1 is established; before the sub-transaction 2 is executed, the savepoint savepoint2 is established; before the sub-transaction 2 is executed, the savepoint savepoint3 is established.

In the embodiment shown in FIG. 2, a lock wait occurs when a transaction is executed to sub-transaction 3.

If the execution of the child transaction 3 occurs for the first time, and the waiting time corresponding to the first lock wait is exceeded, the number of sub-transactions s that need to be rolled back is 1, and the rollback needs to be rolled back to the 3-1+1= The first savepoint before the 3 subtransactions, that is, the first savepoint savepoint3 before the child transaction 3. At the same time, the database needs to release the lock after savepoint3.

If the execution of the sub-transaction 3 occurs for the second time, and the waiting time corresponding to the first lock is exceeded, the number of sub-transactions s that need to be rolled back is 2, and the rollback needs to be rolled back to the 3-2+1= The first savepoint before the 2 subtransactions, that is, the first savepoint savepoint2 before the child transaction 2. At the same time, the database needs to release the lock after savepoint2. In addition, if a storage point is recorded using a linked list or the like in the embodiment of the present application, it is also necessary to delete the save point record after savepoint2.

If the execution of the child transaction 3 occurs for the third time, and the waiting time corresponding to the first lock wait is exceeded, the number of sub-transactions s that need to be rolled back is 3, and the rollback needs to be rolled back to the 3-3+1. =1 The first savepoint before the child transaction, that is, the first savepoint savepoint1 before the child transaction 1. At the same time, the database needs to release the lock after savepoint3. In addition, if a storage point is recorded using a linked list or the like in the embodiment of the present application, it is also necessary to delete the save point record after the savepoint3.

Of course, it should be understood that, as shown in FIG. 2, the identifier of the save point created before each sub-transaction is executed can be saved through the linked list. The save points created by the three sub-transactions in Figure 2 are stored in the linked list in order of execution, corresponding to execution plan 1, execution plan 2, and execution plan 3. The database can find the identifier of the corresponding savepoint from the linked list according to the number of sub-transactions that need to be rolled back.

In addition, it should be understood that in the scenario shown in FIG. 2, it is also possible to record the information of the save point without using a linked list, and to specify the naming rule of the save point. For example, it may be specified that the naming rule of the save point in FIG. 2 is "savepoint" + serial number. In the first rollback, the sequence number of the savepoint that needs to be rolled back is 3-1+1=3. According to the naming rule, the savepoint can be determined to be savepoint3, and so on.

In addition, for the waiting time for the lock waiting for determining whether to time out, it may be specified that the waiting time for each lock waiting is the same, or the number of times the timeout occurs according to the lock waiting, the number of the sub-transaction when the lock waits, and the time when the lock waits. The data operation type involved in the sub-transaction, or the number of records of the data operation involved in the sub-transaction when the lock waits, and the like, comprehensively determine the waiting time of the lock waiting. In addition, the waiting time waiting for can be randomly assigned according to the random number.

In addition, each time a rollback occurs, a wait time can be set. After the wait time elapses after the rollback, the sub-transaction is resumed, so that the transaction holding the lock of the transaction cannot be released in time. As a result, the transaction continues to lock waiting.

It should be noted that the execution bodies of the steps of the method provided by the embodiment shown in FIG. 1 may be the same device, or the method may also be performed by different devices. For example, the execution body of step S110 and step S120 may be device 1, and the execution body of step S130 may be device 2; for example, the execution body of step S110 may be device 1, and the execution body of step S120 and step S130 may be device 2 ;and many more.

FIG. 3 is a schematic structural diagram of an electronic device according to an embodiment of the present application. Referring to FIG. 3, at the hardware level, the electronic device includes a processor, an internal bus, a network interface, a memory, and a non-volatile memory, and may of course include hardware required for other services. The processor reads the corresponding computer program from the non-volatile memory into memory and then runs to form a device that unlocks the user interface at a logical level. Of course, in addition to the software implementation, the present application does not exclude other implementation manners, such as a logic device or a combination of software and hardware, etc., that is, the execution body of the following processing flow is not limited to each logical unit, and may be Hardware or logic device.

FIG. 4 is a schematic structural diagram of an apparatus 400 for processing a database deadlock according to an embodiment of the present application. It should be understood that the device 400 for processing the database deadlock may be a database system or a specific implementation module in the database system, which is not limited herein. Referring to FIG. 4, in a software implementation, the database deadlock device 400 can include a transaction partitioning unit 410, a savepoint creation unit 420, an execution unit 430, and a transaction rollback unit 440. among them,

The transaction dividing unit 410 divides the transaction into N sub-transactions that are sequentially executed, where N is a positive integer greater than one;

The savepoint creation unit 420 creates a savepoint before executing each of the N subtransactions;

Execution unit 430 sequentially executes the N sub-transactions;

When the nth child transaction of the N child transactions has a lock wait and the waiting time is greater than the first wait time corresponding to the nth child transaction, the transaction rollback unit 440 rolls back the transaction to the rollback savepoint, where a positive integer less than or equal to N, the rollback savepoint is a savepoint created before the execution of the nth child transaction;

The execution unit 430 also continues to sequentially execute the sub-transactions of the N sub-transactions after the first save point after the transaction rollback unit 440 rolls back the to-be-executed transaction to the first savepoint.

FIG. 5 is a schematic structural diagram of an apparatus 400 for processing a database deadlock according to another embodiment of the present application. Optionally, as shown in FIG. 5, the apparatus 400 may further include a determining unit 450, when the nth sub-transaction of the N sub-transactions has a lock wait for the i-th time and the waiting time is greater than the first wait corresponding to the n-th sub-transaction The determining unit 450 determines the rollback savepoint according to the number of sub-transactions s that need to be rolled back according to the ith lock, and the mapping relationship between s and i is preset, and both i and s are positive integers.

Further, the determining unit 450 determines, according to the number of sub-transactions that need to be rolled back corresponding to the ith lock, the rollback savepoint includes: the determining unit 450 may determine that the first savepoint before the ns sub-transaction is the The first save point, where s<n; or, the determining unit 45 may determine that the save point before the first sub-transaction is the first save point, where s ≥ n.

Optionally, the first waiting time is set by a user of the database system of the firm; or the first waiting time is set according to a random number.

Optionally, the executing unit 430 continues to sequentially execute the sub-transactions of the N sub-transactions after the first save point after specifically rolling back to the first save point and waiting for the second waiting time. Further, the second waiting time is set according to a SQL type of the structured query language involved in the office; or the second waiting time is set by a user of the database system of the firm; or, the second The waiting time is set according to the random number.

Optionally, as an embodiment, the savepoint created by each of the N sub-transactions before execution is named according to a sequence number of the savepoint and a predetermined rule, and the rollback savepoint is based on the rollback savepoint. The serial number and the predetermined rule are determined.

Alternatively, optionally, as another embodiment, the save points created by each of the N sub-transactions before execution are stored in a linked list in a sequential order, and the roll-back save points are determined by searching the linked list. Further, as shown in FIG. 5, the device 400 may further include a deleting unit 460. If the savepoint creation unit records the savepoint in sequence when creating a savepoint corresponding to each of the N child transactions; the delete unit may roll back the transaction to the back in the transaction rollback unit When you save a savepoint, delete the record of the savepoint created after the rollback savepoint.

The device 400 handling the database deadlock can also perform the method of FIG. 1 and implement database or process database deadlock The functions of the embodiment shown in FIG. 1 and FIG. 2 are not described herein again.

The present application also discloses a database system comprising the apparatus 400 for processing database deadlocks of the embodiment shown in FIG. 4 or 5.

In the 1990s, improvements to a technology could clearly distinguish between hardware improvements (eg, improvements to circuit structures such as diodes, transistors, switches, etc.) or software improvements (for process flow improvements). However, as technology advances, many of today's method flow improvements can be seen as direct improvements in hardware circuit architecture. Designers almost always get the corresponding hardware circuit structure by programming the improved method flow into the hardware circuit. Therefore, it cannot be said that the improvement of a method flow cannot be implemented by hardware entity modules. For example, a Programmable Logic Device (PLD) (such as a Field Programmable Gate Array (FPGA)) is an integrated circuit whose logic function is determined by the user programming the device. Designers program themselves to "integrate" a digital system on a single PLD without having to ask the chip manufacturer to design and fabricate a dedicated integrated circuit chip. Moreover, today, instead of manually making integrated circuit chips, this programming is mostly implemented using "logic compiler" software, which is similar to the software compiler used in programming development, but before compiling The original code has to be written in a specific programming language. This is called the Hardware Description Language (HDL). HDL is not the only one, but there are many kinds, such as ABEL (Advanced Boolean Expression Language). AHDL (Altera Hardware Description Language), Confluence, CUPL (Cornell University Programming Language), HDCal, JHDL (Java Hardware Description Language), Lava, Lola, MyHDL, PALASM, RHDL (Ruby Hardware Description Language), etc., are currently the most commonly used VHDL (Very-High-Speed Integrated Circuit Hardware Description Language) and Verilog. It should also be apparent to those skilled in the art that the hardware flow for implementing the logic method flow can be easily obtained by simply programming the method flow into the integrated circuit with a few hardware description languages.

The controller can be implemented in any suitable manner, for example, the controller can take the form of, for example, a microprocessor or processor and a computer readable medium storing computer readable program code (eg, software or firmware) executable by the (micro)processor. In the form of logic gates, switches, application specific integrated circuits (ASICs), programmable logic controllers, and embedded microcontrollers, examples of controllers include, but are not limited to, the following microcontrollers: ARC 625D, Atmel AT91SAM, The Microchip PIC18F26K20 and the Silicone Labs C8051F320, the memory controller can also be implemented as part of the memory's control logic. Those skilled in the art will also appreciate that in addition to implementing the controller in purely computer readable program code, the controller can be logically programmed by means of logic gates, switches, ASICs, programmable logic controllers, and embedding. Microcontroller, etc. The form to achieve the same functionality. Such a controller can therefore be considered a hardware component, and the means for implementing various functions included therein can also be considered as a structure within the hardware component. Or even a device for implementing various functions can be considered as a software module that can be both a method of implementation and a structure within a hardware component.

The system, device, module or unit illustrated in the above embodiments may be implemented by a computer chip or an entity, or by a product having a certain function. A typical implementation device is a computer. Specifically, the computer can be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smart phone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or A combination of any of these devices.

For the convenience of description, the above devices are described separately by function into various units. Of course, the functions of each unit may be implemented in the same software or software and/or hardware when implementing the present application.

Those skilled in the art will appreciate that embodiments of the present application can be provided as a method, system, or computer program product. Thus, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment in combination of software and hardware. Moreover, the application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) including computer usable program code.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (system), and computer program products according to embodiments of the present application. It will be understood that each flow and/or block of the flowchart illustrations and/or FIG. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing device to produce a machine for the execution of instructions for execution by a processor of a computer or other programmable data processing device. Means for implementing the functions specified in one or more of the flow or in a block or blocks of the flow chart.

The computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture comprising the instruction device. The apparatus implements the functions specified in one or more blocks of a flow or a flow and/or block diagram of the flowchart.

These computer program instructions can also be loaded onto a computer or other programmable data processing device such that a series of operational steps are performed on a computer or other programmable device to produce computer-implemented processing for execution on a computer or other programmable device. The instructions provide steps for implementing the functions specified in one or more of the flow or in a block or blocks of a flow diagram.

In a typical configuration, a computing device includes one or more processors (CPUs), input/output interfaces, network interfaces, and memory.

The memory may include non-persistent memory, random access memory (RAM), and/or non-volatile memory in a computer readable medium, such as read only memory (ROM) or flash memory. Memory is an example of a computer readable medium.

Computer readable media includes both permanent and non-persistent, removable and non-removable media. Information storage can be implemented by any method or technology. The information can be computer readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read only memory. (ROM), electrically erasable programmable read only memory (EEPROM), flash memory or other memory technology, compact disk read only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, Magnetic tape cartridges, magnetic tape storage or other magnetic storage devices or any other non-transportable media can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary storage of computer readable media, such as modulated data signals and carrier waves.

It is also to be understood that the terms "comprises" or "comprising" or "comprising" or any other variations are intended to encompass a non-exclusive inclusion, such that a process, method, article, Other elements not explicitly listed, or elements that are inherent to such a process, method, commodity, or equipment. An element defined by the phrase "comprising a ..." does not exclude the presence of additional equivalent elements in the process, method, item, or device including the element.

Those skilled in the art will appreciate that embodiments of the present application can be provided as a method, system, or computer program product. Thus, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment in combination of software and hardware. Moreover, the application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) including computer usable program code.

The application can be described in the general context of computer-executable instructions executed by a computer, such as a program module. Generally, program modules include routines, programs, objects, components, data structures, and the like that perform particular tasks or implement particular abstract data types. The present application can also be practiced in distributed computing environments where tasks are performed by remote processing devices that are connected through a communication network. In a distributed computing environment, program modules can be located in both local and remote computer storage media including storage devices.

The various embodiments in this specification are described in a progressive manner, with similar parts between the various embodiments. It is sufficient to refer to each other, and each embodiment focuses on differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the description of the method embodiment.

The above description is only an embodiment of the present application and is not intended to limit the application. Various changes and modifications can be made to the present application by those skilled in the art. Any modifications, equivalents, improvements, etc. made within the spirit and scope of the present application are intended to be included within the scope of the appended claims.

Claims

A method for processing a database deadlock, comprising:

Dividing the transaction into N sub-transactions executed sequentially, where N is a positive integer greater than one;

Creating a savepoint before each of the N sub-transactions is executed;

Executing the N sub-transactions in sequence;

When the nth sub-transaction of the N sub-transactions has a lock wait and the waiting time is greater than the first waiting time corresponding to the n-th sub-transaction, the transaction is rolled back to the rollback savepoint, where n is less than Or a positive integer equal to N, the rollback savepoint is a savepoint created before the execution of the nth child transaction;

The sub-transactions after the rollback savepoint in the N sub-transactions are continued to be sequentially executed.
The method of claim 1 wherein the method further comprises:

When the nth sub-transaction of the N sub-transactions has a lock wait for the i-th time and the waiting time is greater than the first waiting time corresponding to the n-th sub-transaction, the sub-transactions that need to be rolled back according to the i-th lock wait The number s is determined by the rollback savepoint, and the mapping relationship between s and i is preset, and both i and s are positive integers.
The method of claim 2, wherein the determining, according to the number of sub-transactions s that need to be rolled back according to the ith lock, determining the rollback savepoint comprises:

When s<n, determining that the first savepoint before the n-s+1th sub-transaction is the rollback savepoint; or

When s ≥ n, it is determined that the save point before the first sub-transaction is the roll-back save point.
A method according to any one of claims 1 to 3, wherein

The first waiting time is set by a user of the database system in which the firm is located; or

The first waiting time is set according to a random number.
The method of claim 4, wherein the continuing to sequentially execute the sub-transactions of the N sub-transactions after the rollback savepoint comprises: rolling back to the rollback savepoint and waiting for the After the two waiting times, the sub-transactions after the rollback savepoint in the N sub-transactions are sequentially executed.
The method of claim 5 wherein:

The second waiting time is set according to a SQL type of a structured query language involved in the office; or

The second waiting time is set by a user of the database system of the firm; or

The second waiting time is set according to a random number.
The method according to claim 6, wherein the method further comprises: when creating a save point corresponding to each of the N sub-transactions, sequentially recording the save point, and The transaction is rolled back to When the save point is rolled back, the record of the save point created after the rollback save point is deleted.
The method of claim 7 wherein:

The save points created by each of the N sub-transactions before execution are stored in a linked list in a sequential order, and the roll-back save points are determined by looking up the linked list.
The method of claim 8 wherein:

The savepoint created by each of the N sub-transactions before execution is named according to the sequence number of the savepoint and a predetermined rule, and the rollback savepoint is based on the sequence number of the rollback savepoint and the predetermined The rules are determined.
An apparatus for processing a database deadlock, comprising: a transaction division unit, an execution unit, a savepoint creation unit, and a transaction rollback unit, wherein

The transaction dividing unit divides the transaction into N sub-transactions executed sequentially, where N is a positive integer greater than one;

The execution unit sequentially executes the N sub-transactions;

The savepoint creation unit creates a savepoint before executing each of the N subtransactions;

When the nth sub-transaction of the N sub-transactions has a lock wait and the waiting time is greater than the first waiting time corresponding to the n-th sub-transaction, the transaction rollback unit rolls back the transaction to the roll-back savepoint Where n is a positive integer less than or equal to N, and the rollback savepoint is a savepoint created before the execution of the nth child transaction;

The execution unit further continues to sequentially execute the sub-transactions of the N sub-transactions after the rollback savepoint after the transaction rollback unit rolls back the transaction to the rollback savepoint.
The device according to claim 10, wherein said device further comprises a determining unit,

When the nth sub-transaction of the N sub-transactions has a lock waiting for the i-th time and the waiting time is greater than the first waiting time corresponding to the n-th sub-transaction, the determining unit needs to roll back according to the need of the i-th lock waiting The number of child transactions s, determine the rollback savepoint, the mapping relationship between s and i is preset, and i and s are both positive integers.
The apparatus according to claim 11, wherein the determining unit determines, according to the number of sub-transactions s that need to be rolled back corresponding to the i-th lock, determining that the rollback savepoint comprises:

The determining unit determines that the first save point before the n-s+1th sub-transaction is the rollback save point, where s<n;

The determining unit determines that the save point before the first sub-transaction is the roll-back save point, where s ≥ n.
A device according to any of claims 10-12, wherein

The first waiting time is set by a user of the database system in which the firm is located; or

The first waiting time is set according to a random number.
The apparatus according to claim 13, wherein the execution unit continues to sequentially perform the rollback in the N sub-transactions after rolling back to the rollback savepoint and waiting for a second waiting time. Save the child transaction after the point.
The device of claim 14 wherein:

The second waiting time is set according to a SQL type of a structured query language involved in the office; or

The second waiting time is set by a user of the database system of the firm; or

The second waiting time is set according to a random number.
The device according to claim 15, wherein said device further comprises a deleting unit, wherein

The savepoint creation unit further records the savepoints in sequence when creating a savepoint corresponding to each of the N child transactions;

The deleting unit further deletes the record of the save point created after the rollback save point when the transaction rollback unit rolls back the transaction to the rollback savepoint.
The device of claim 16 wherein:

The save points created by each of the N sub-transactions before execution are stored in a linked list in a sequential order, and the roll-back save points are determined by looking up the linked list.
The device of claim 17 wherein:

The savepoint created by each of the N sub-transactions before execution is named according to the sequence number of the savepoint and a predetermined rule, and the rollback savepoint is based on the sequence number of the rollback savepoint and the predetermined The rules are determined.