WO2016197870A1

WO2016197870A1 - Method and device for processing ddl statement in relational database

Info

Publication number: WO2016197870A1
Application number: PCT/CN2016/084624
Authority: WO
Inventors: 赵建伟
Original assignee: 阿里巴巴集团控股有限公司
Priority date: 2015-06-11
Filing date: 2016-06-03
Publication date: 2016-12-15
Also published as: CN106294512A

Abstract

Provided are a method and device for processing a DDL statement in a relational database. Specifically, the method comprises: acquiring a DDL statement regarding a target table submitted by a user, wherein the DDL statement comprises a corresponding item of information waiting to be set (S1); requesting an exclusive MDL lock corresponding to the target table (S2); if requesting the exclusive MDL lock fails, exiting from the DDL statement according to the information (S3). Compared with the conventional art, the method addresses a block that arises when concurrently executing data definition language (DDL) and data manipulation language (DML) statements in a relational database, thereby avoiding database-related application access blockage or service interruption, enhancing execution efficiency of database language statements, and improving reliability of the database.

Description

Method and device for processing DDL statement in relational database

The present application claims priority to Chinese Patent Application No. 201510318978.7, entitled "Method and Apparatus for Handling DDL Statements in Relational Databases", filed on June 11, 2015, the entire contents of which are incorporated herein by reference. In the application.

Technical field

The present invention relates to the field of computers, and in particular, to a technique for processing DDL statements in a relational database.

Background technique

In the operation and maintenance process of the relational database, when the data definition language DDL and the data manipulation language DML are executed concurrently, the incompatibility problems caused by the different types of MDL locks applied for each other cause the two statements to be generated during execution. Blocked, blocking the execution of subsequent statements. In the prior art, the DDL statement can be set to make the DDL statement fail quickly when the statement conflict occurs concurrently, thereby solving the statement concurrent execution blocking.

However, in the prior art, the DDL statement can only be set at the paragraph or global level, and the flexible operation of the statement level cannot be performed. In the operation process, the operation and maintenance personnel may cause the application access to be blocked due to the excessive blocking time of the statement concurrent execution. Business disruption.

Summary of the invention

It is an object of the present application to provide a method and apparatus for processing DDL statements in a relational database.

According to an aspect of the present application, a method for processing a DDL statement in a relational database is provided, comprising:

Obtaining a DDL statement submitted by the user about the target table, where the DDL statement includes corresponding waiting setting information;

Applying an exclusive MDL lock corresponding to the target table;

If the application for the exclusive MDL lock fails, the exit processing is performed on the DDL statement according to the waiting setting information.

According to another aspect of the present application, there is also provided an apparatus for processing a DDL statement in a relational database, comprising:

a first device, configured to acquire a DDL statement submitted by the user about the target table, where the DDL statement includes corresponding waiting setting information;

a second device, configured to apply for an exclusive MDL lock corresponding to the target table;

And a third device, configured to perform an exit process on the DDL statement according to the waiting setting information if the application for the exclusive MDL lock fails.

Compared with the prior art, the present application requests the exclusive MDL lock corresponding to the target table by acquiring the DDL statement submitted by the user about the target table and the corresponding waiting information set in the target table, and if the application fails, according to the set waiting The DDL statement in the information performs the exit processing, solves the data definition language DDL in the system database and the data manipulation language DML concurrently executes the blocking problem, thereby avoiding the blocked access or business interruption of the database associated application, improving the execution efficiency of the database language, and improving the database. reliability.

DRAWINGS

Other features, objects, and advantages of the present invention will become more apparent from the Detailed Description of Description

1 shows a schematic diagram of an apparatus for processing DDL statements in a relational database, in accordance with an aspect of the present application;

2 shows a flow chart of a method for processing DDL statements in a relational database in accordance with another aspect of the present application.

The same or similar reference numerals in the drawings denote the same or similar components.

detailed description

The invention is further described in detail below with reference to the accompanying drawings.

In a typical configuration of the present application, the terminal, the device of the service network, and the trusted party each include 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, CD-ROM, digital versatile disc (DVD) or other optical storage, magnetic tape cartridge, magnetic tape storage or other magnetic storage device or any other non-transportable media that can be used for storage can be calculated Information accessed by the device. As defined herein, computer readable media does not include non-transitory computer readable media, such as modulated data signals and carrier waves.

1 shows a schematic diagram of an apparatus 1 for processing DDL statements in a relational database, in accordance with an aspect of the present application. The device 1 comprises a first device 11, a second device 12 and a third device 13.

The first device 11 of the device 1 is configured to acquire a DDL statement submitted by a user about a target table, where the DDL statement includes corresponding waiting setting information; and the second device 12 is configured to apply for the target table. The exclusive MDL lock; the third device is configured to perform an exit process on the DDL statement according to the waiting setting information if the application for the exclusive MDL lock fails.

Specifically, the first device 11 is configured to acquire a DDL statement submitted by the user about the target table, where the DDL statement includes corresponding waiting setting information. Wherein, the manner of obtaining the DDL statement submitted by the user about the target table may be performed by a database management system, and the DDL statement is a database definition language, and the DDL statement about the target table is executed before the execution in order to provide a concurrent access to the dictionary object cache in the memory. The protection, as well as the mutual exclusion of some database language operations, need to apply for MDL locks to protect the data in the table when the statement is executed. The waiting setting information is setting information of a corresponding execution action when the DDL statement requests the MDL lock to be blocked, and includes an action performed after the user desires that the DDL statement is blocked, and the action includes continuing to wait or immediately exit waiting for related operations. For example, when a DDL statement requests an exclusive MDL lock, an execution conflict occurs with a DML statement that previously applied for a shared-level MDL lock. Therefore, after entering the lock waiting queue and waiting for the DML statement to execute, the MDL lock application is performed, and the subsequent DML statements are all due to The DDL statement waits and enters the lock waiting queue to cause blocking. If the DDL statement includes the corresponding waiting setting information, when the example DDL statement enters the lock waiting queue, it waits for a certain time to exit or immediately exit according to the waiting setting information. In order to avoid the blocking or interruption of the database business caused by the blocking of the application MDL lock statement.

Preferably, the waiting setting information includes at least one of the following: a set waiting time; zero waiting. The set waiting time is set in the DDL statement to wait for the set time. If the set time is exceeded, the execution task of the DDL statement fails to be exited immediately. For example, the DDL statement is set to Alter table test wait 1 add col1 number, that is, Waiting for 1 second after failing to apply for the MDL lock, so that it is deleted in the MDL lock waiting queue, the blocked application sharing level DML language can therefore reduce the waiting time or the current statement when the current MDL lock is the sharing level carried out. Zero wait, that is, the DDL statement execution task fails to exit immediately after setting the feedback of the failed application for the MDL lock in the DDL statement. For example, the DDL statement is set to Alter table test no_wait add col1 Number also enables subsequent DML languages in the MDL lock wait queue to reduce latency or co-execute with the current statement when the current MDL lock is shared, reducing the time that database-related services are unavailable.

Those skilled in the art should be able to understand that the waiting time of the above setting and the manner of zero waiting are only examples, and other existing or future possible waiting times according to the setting and zero waiting mode may be applied to The invention is also intended to be included within the scope of the invention, and is hereby incorporated by reference.

Next, the second device 12 is configured to apply for an exclusive MDL lock corresponding to the target table. Wherein, the exclusive MDL lock is a conflict that the DDL statement conflicts when the target table that is the object of the statement execution is not executed concurrently with other database languages (for example, the database manipulation language DML) before being executed, for example, The DDL statement performs an insert operation on the same target table when the entire table delete of the target table is performed, and the concurrent execution conflict is generated at this time. To avoid this, the DDL statement in the relational database will be executed before the execution. Applying an exclusive MDL lock makes it impossible for DDL statements to be executed outside the target table at the time of execution, thereby improving the execution efficiency of the database language and protecting the data in the table.

Next, the third device 13 is configured to perform an exit process on the DDL statement according to the waiting setting information if the application for the exclusive MDL lock fails. Because the DDL statement applies for an exclusive MDL lock, when the statement in the corresponding lock holding queue of the target table operation corresponds to the shared-level MDL lock, the application for the shared DDL statement fails for the exclusive MDL lock, and the DDL statement enters the lock waiting queue. At this time, the waiting setting information in the DDL statement is triggered, and the triggering method includes setting the feedback information after the acquisition of the MDL lock application fails, starting the setting information corresponding program, reading the setting information, and performing the setting action accordingly. The waiting setting information includes an action performed by the user after the DDL statement is blocked, and the action includes continuing to wait or immediately exiting waiting and other related operations. After waiting for the setting information to be triggered, the waiting information is waited according to the waiting setting information. The time exits or immediately exits the execution of the DDL statement, thereby avoiding the DML statement that the DDL statement can use the shared-level MDL lock after waiting too long in the lock wait queue. The lock holding queue described above is a relational database, and the database language is in the queue after the application for the MDL lock is successful. Accordingly, the lock waiting queue applies for the MDL lock for the database language because the applied lock type is mutually exclusive and fails. Wait for the MDL lock to hold the statement and continue to apply for the MDL lock queue.

Those skilled in the art should understand that the manner of performing the exit processing on the DDL statement according to the waiting setting information is only an example, and other existing or future possible executions may be performed to exit the DDL statement according to the waiting setting information. The manner of treatment, as applicable to the present invention, is also intended to be included within the scope of the present invention and is hereby incorporated by reference.

Preferably, the third device is configured to: execute the DDL statement if the application for the exclusive MDL lock is successful. When the DDL statement applies for an exclusive MDL lock, there are no other statements that hold the MDL with the exclusive MDL mutually exclusive type. The lock, the DDL statement acquires the exclusive MDL lock, enters the lock holding queue and then executes the statement content, and performs corresponding operations on the target table.

More preferably, the waiting setting information includes a set waiting time, wherein the third device is configured to: if the application for the exclusive MDL lock fails, wait for the waiting time to wait for the exclusive MDL lock again. If the application for the exclusive MDL lock fails, the execution of the DDL statement is exited. That is, before the set waiting time starts to execute, immediately before the DDL statement execution task fails to exit, the setting information of re-applying the MDL lock may be added, that is, after waiting for the set time, for example, after waiting for 1 second, after waiting for 1 second, Continue to initiate the application for the MDL lock. If the MDL lock is not held at this time, the application can be successfully applied and executed with the exclusive MDL lock. If the MDL lock is still held, and the application is with DDL. If the MDL lock conflicts, the execution immediately causes the DDL statement execution task to fail to exit, thereby increasing the probability that the DDL applies for the MDL lock, and improving the application efficiency of the MDL lock.

Further, the waiting setting information includes zero waiting, wherein the third device is configured to: quit the execution processing of the DDL statement if the exclusive MDL lock fails to be applied. That is, after the DDL statement obtains the feedback of applying for the exclusive MDL lock failure, according to the zero waiting setting, the DDL statement execution task is immediately defeated, so that the DDL statement is deleted in the MDL lock waiting queue, so the MDL lock waiting queue can be reduced. Waiting time for other statements to avoid database related business interruption or application access blocked due to long waiting time.

An apparatus 1 (not shown) for processing DDL statements in a relational database in accordance with a preferred embodiment of the present application. The device 1 comprises a first device, a second device and a third device, wherein both the first device and the second device add a data manipulation language DML to the first device 11 and the second device 12 shown in FIG. Processing, the third device includes a first unit, the first unit is configured to: after exiting execution processing on the DDL statement, add at least one of the DML statements to a lock holding queue of the MDL lock or The lock waits for the queue.

Specifically, the first device is further configured to acquire a DML statement submitted by the user about the target table, where the third device further includes a first unit, after exiting execution processing on the DDL statement, Adding at least one of the DML statements to a lock holding queue or a lock waiting queue of the MDL lock. The acquired database language of the target table includes DML in addition to the DDL. Therefore, after exiting the execution process of the DDL statement, the DDL statement is deleted from the MDL lock waiting queue, and subsequently in the MDL lock waiting queue. The DML statements in the order will be processed in the order in which they are arranged. At least one DML statement is added to the MDL lock hold or lock wait queue according to the type requirements of the MDL lock in the queue. For example, if the current MDL lock holds the database language in the queue. The MDL lock type held by the statement is not mutually exclusive and shareable with the DML statement in the lock wait queue. Then, the DML statement is added to the lock holding queue according to the order until the database statement with mutual exclusion needs appears, and the statement is excluded. MDL lock Outside the holding queue, it still remains in the MDL lock waiting queue. If the MDL lock type held by the database language statement in the current MDL lock holding queue is mutually exclusive with the DML statement in the lock waiting queue, the obtained DML statement is added. Go to the MDL lock wait queue to wake up blocked DML statements, making database-related application access efficient or faster.

Preferably, the first unit is configured to: after exiting execution processing on the DDL statement, when the lock holding queue and the statement in the lock waiting queue all correspond to the sharing level MDL lock, At least one of the DML statements is added to the lock holding queue. The DML statement includes the DML statement processed again and processed for the first time, that is, the statement executed before the lock waiting queue position where the DML statement is located after exiting the execution of the DDL statement, and the statement in the currently held queue. Corresponding to the shared and MDL locks, the DML statement can be added to the lock holding queue together with the statement in the lock waiting queue before the lock waiting queue position. For example, dml1 and dml2 refer to two DML statements. There are shared-level MDL locks, dml3, dml4, and dml5 refer to the DML statements in the lock wait queue, which need to apply for the shared-level MDL lock. dml6 refers to the DML that the newly acquired user needs to apply for the shared-level MDL lock. In the English drama, after the DDL statement arranged before dml3 is deleted, dml3 to dm16 can be added to the lock holding queue, so that the DML statement is executed after the DDL statement is executed, and the DML statement is executed because the same is the application for the shared-level MDL lock. accelerate.

More preferably, the second device is further configured to add the DML statement to a lock waiting queue of the MDL lock, wherein the first unit is configured to: after exiting execution processing on the DDL statement, when When the lock holding queue and the statement in the lock waiting queue all correspond to the MDL lock of the sharing level, at least one of the DML statements is added from the lock waiting queue to the lock holding queue. When a DDL statement is applied to an MDL lock, because the DDL statement is applied for an exclusive MDL lock, the DML statement acquired at this time needs to apply for the shared-level MDL lock and the exclusive MDL lock applied by the DDL statement to be mutually exclusive. That is, even if the application is successful, the DML statement cannot share the MDL lock with the DML statement. Therefore, the DML statement acquired at this time is added to the lock waiting queue of the MDL. When the DDL statement is executed and exited, the DML statement added to the MDL lock wait queue may be added to the lock holding queue by the lock waiting queue, and if there is a DML statement in the subsequent lock waiting queue, since Apply for a shared-level MDL lock, so they are added to the lock holding queue until the statement that requests the mutual exclusion level MDL lock appears to stop adding.

Further, the first unit is configured to: after exiting execution processing on the DDL statement, when the lock holding queue or the lock waiting queue has a statement corresponding to the exclusive MDL lock, the DML is At least one of the statements is added to the lock wait queue. When there is a DDL statement in the application for the MDL lock, because the DDL statement is applied for an exclusive MDL lock, the DML statement acquired at this time needs to apply for the shared-level MDL lock and DDL. The exclusive MDL locks applied by the statement are mutually exclusive, that is, the DML statement cannot share the MDL lock with the DML statement even if the application is successful. Therefore, the DML statement acquired at this time is added to the MDL lock waiting queue, and the same MDL lock waiting queue is also There are other DDL statements for applying for exclusive MDL locks. When the DDL statement is executed and exited, the DML statement added to the MDL lock wait queue has an exclusive MDL lock in the previous queue, or the current MDL lock holding queue statement holds an exclusive MDL lock. At least one of the MDL statements obtained at this time is added to the lock waiting queue.

2 shows a flow chart of a method for processing DDL statements in a relational database in accordance with another aspect of the present application. Wherein, step S1, step S2 and step S3 are included.

In the step S1, the device 1 acquires a DDL statement submitted by the user about the target table, where the DDL statement includes corresponding waiting setting information; in step S2, the device 1 applies for the exclusive MDL lock corresponding to the target table; In step S3, if the device 1 fails to apply for the exclusive MDL lock, the device 1 performs an exit process on the DDL statement according to the waiting setting information.

Specifically, the device 1 acquires a DDL statement submitted by the user regarding the target table in step S1, wherein the DDL statement includes corresponding waiting setting information. Wherein, the manner of obtaining the DDL statement submitted by the user about the target table may be performed by a database management system, and the DDL statement is a database definition language, and the DDL statement about the target table is executed before the execution in order to provide a concurrent access to the dictionary object cache in the memory. The protection, as well as the mutual exclusion of some database language operations, need to apply for MDL locks to protect the data in the table when the statement is executed. The waiting setting information is setting information of a corresponding execution action when the DDL statement requests the MDL lock to be blocked, and includes an action performed after the user desires that the DDL statement is blocked, and the action includes continuing to wait or immediately exit waiting for related operations. For example, when a DDL statement requests an exclusive MDL lock, an execution conflict occurs with a DML statement that previously applied for a shared-level MDL lock. Therefore, after entering the lock waiting queue and waiting for the DML statement to execute, the MDL lock application is performed, and the subsequent DML statements are all due to The DDL statement waits and enters the lock waiting queue to cause blocking. If the DDL statement includes the corresponding waiting setting information, when the example DDL statement enters the lock waiting queue, it waits for a certain time to exit or immediately exit according to the waiting setting information. In order to avoid the blocking or interruption of the database business caused by the blocking of the application MDL lock statement.

Preferably, the waiting setting information includes at least one of the following: a set waiting time; zero waiting. The set waiting time is set in the DDL statement to wait for the set time. If the set time is exceeded, the execution task of the DDL statement fails to be exited immediately. For example, the DDL statement is set to Alter table test wait 1 add col1 number, that is, Waiting for 1 second after failing to apply for the MDL lock, so that it is deleted in the MDL lock waiting queue, the blocked application sharing level DML language can therefore reduce the waiting time or the current language when the current MDL lock is shared The sentences are executed together. Zero wait, that is, the DDL statement execution task fails to be exited immediately after the feedback of the application MDL lock failure is set in the DDL statement. For example, the DDL statement is set to Alter table test no_wait add col1 number, and the subsequent DDL statement waits in the MDL lock waiting queue. The DML language can reduce latency or co-execute with the current statement when the current MDL lock is shared, reducing the time that database-related services are unavailable.

Next, in step S2, the device 1 applies for an exclusive MDL lock corresponding to the target table. Wherein, the exclusive MDL lock is a conflict that the DDL statement conflicts when the target table that is the object of the statement execution is not executed concurrently with other database languages (for example, the database manipulation language DML) before being executed, for example, The DDL statement performs an insert operation on the same target table when the entire table delete of the target table is performed, and the concurrent execution conflict is generated at this time. To avoid this, the DDL statement in the relational database will be executed before the execution. Applying an exclusive MDL lock makes it impossible for DDL statements to be executed outside the target table at the time of execution, thereby improving the execution efficiency of the database language and protecting the data in the table.

Next, in step S3, if the device 1 fails to apply for the exclusive MDL lock, the device 1 performs an exit process on the DDL statement according to the waiting setting information. Because the DDL statement applies for an exclusive MDL lock, when the statement in the corresponding lock holding queue of the target table operation corresponds to the shared-level MDL lock, the application for the shared DDL statement fails for the exclusive MDL lock, and the DDL statement enters the lock waiting queue. At this time, the waiting setting information in the DDL statement is triggered, and the triggering method includes setting the feedback information after the acquisition of the MDL lock application fails, starting the setting information corresponding program, reading the setting information, and performing the setting action accordingly. The waiting setting information includes an action performed by the user after the DDL statement is blocked, and the action includes continuing to wait or immediately exiting waiting and other related operations. After waiting for the setting information to be triggered, the waiting information is waited according to the waiting setting information. The time exits or immediately exits the execution of the DDL statement, thereby avoiding the DML statement that the DDL statement can use the shared-level MDL lock after waiting too long in the lock wait queue. The lock holding queue described above is a relational database, and the database language is in the queue after the application for the MDL lock is successful. Accordingly, the lock waiting queue applies for the MDL lock for the database language because the applied lock type is mutually exclusive and fails. Wait for the MDL lock to hold the statement and continue to apply for the MDL lock queue.

Preferably, in step S3, if the device 1 successfully requests the exclusive MDL lock, the DDL statement is executed. That is, when the DDL statement applies for the exclusive MDL lock, no other statement holds the MDL lock with the exclusive MDL mutual exclusion type. The DDL statement acquires the exclusive MDL lock, enters the lock holding queue and then executes the statement content, and performs corresponding operations on the target table.

More preferably, the waiting setting information includes a set waiting time, wherein, in step S3, if the device 1 fails to apply for the exclusive MDL lock, and waits for the waiting time, the application further requests the exclusive MDL lock; Still applying for the exclusive MDL lock fails, exiting the execution processing of the DDL statement. That is, before the set waiting time starts to execute, immediately before the DDL statement execution task fails to exit, the setting information of re-applying the MDL lock may be added, that is, after waiting for the set time, for example, after waiting for 1 second, after waiting for 1 second, Continue to initiate the application for the MDL lock. If the MDL lock is not held at this time, the application can be successfully applied and executed with the exclusive MDL lock. If the MDL lock is still held, and the application is with DDL. If the MDL lock conflicts, the execution immediately causes the DDL statement execution task to fail to exit, thereby increasing the probability that the DDL applies for the MDL lock, and improving the application efficiency of the MDL lock.

Further, the waiting setting information includes zero waiting, wherein, in step S3, if the device 1 fails to apply for the exclusive MDL lock, the execution processing of the DDL statement is exited. That is, after the DDL statement obtains the feedback of applying for the exclusive MDL lock failure, according to the zero waiting setting, the DDL statement execution task is immediately defeated, so that the DDL statement is deleted in the MDL lock waiting queue, so the MDL lock waiting queue can be reduced. Waiting time for other statements to avoid database related business interruption or application access blocked due to long waiting time.

A method flow (not shown) for processing DDL statements in a relational database in accordance with a preferred embodiment of the present application. The process includes a step S1, a step S2, and a step S3, wherein the steps S1 and S2 both increase the processing of the data manipulation language DML based on the steps S1 and S2 shown in FIG. 2, and the step S3 includes the step S31. After the device 1 exits the execution processing of the DDL statement in step S31, at least one of the DML statements is added to the lock holding queue or the lock waiting queue of the MDL lock.

Specifically, the device 1 further acquires a DML statement submitted by the user about the target table in step S1, wherein step S3 further includes step S31, in which the device 1 exits execution processing on the DDL statement. Thereafter, at least one of the DML statements is added to a lock holding queue or a lock waiting queue of the MDL lock. The acquired database language of the target table includes DML in addition to the DDL. Therefore, after exiting the execution process of the DDL statement, the DDL statement is deleted from the MDL lock waiting queue, and subsequently in the MDL lock waiting queue. The DML statements in the order will be processed in the order in which they are arranged. At least one DML statement is added to the MDL lock hold or the lock wait queue according to the type requirements of the MDL lock in the queue, for example, if the current MDL lock holds the queue. The MDL lock type held by the database language statement is not mutually exclusive and shareable with the DML statement in the lock wait queue, then the DML statement is added to the lock holding queue according to the order until a database statement with mutually exclusive requirements appears, and the The statement is excluded from the MDL lock holding queue and remains in the MDL lock waiting queue. If the MDL lock type held by the database language statement in the current MDL lock holding queue is mutually exclusive with the DML statement in the lock waiting queue, then the statement will be The obtained DML statement is added to the MDL lock waiting queue, thereby awakening the blocked DML statement, so that the database related application access efficiency is improved or the business speed is accelerated.

Preferably, after the device 1 exits the execution processing of the DDL statement in step S31, when the lock holding queue and the statement in the lock waiting queue all correspond to the sharing level MDL lock, the At least one of the DML statements is added to the lock holding queue. The DML statement includes the DML statement processed again and processed for the first time, that is, the statement executed before the lock waiting queue position where the DML statement is located after exiting the execution of the DDL statement, and the statement in the currently held queue. Corresponding to the shared and MDL locks, the DML statement can be added to the lock holding queue together with the statement in the lock waiting queue before the lock waiting queue position. For example, dml1 and dml2 refer to two DML statements. There are shared-level MDL locks, dml3, dml4, and dml5 refer to the DML statements in the lock wait queue, which need to apply for the shared-level MDL lock. dml6 refers to the DML that the newly acquired user needs to apply for the shared-level MDL lock. In the English drama, after the DDL statement arranged before dml3 is deleted, dml3 to dm16 can be added to the lock holding queue, so that the DML statement is executed after the DDL statement is executed, and the DML statement is executed because the same is the application for the shared-level MDL lock. accelerate.

More preferably, the device 1 also adds the DML statement to the lock waiting queue of the MDL lock in step S2, wherein after the device 1 exits the execution processing of the DDL statement in step S31, when When the lock holding queue and the statement in the lock waiting queue all correspond to the MDL lock of the sharing level, at least one of the DML statements is added from the lock waiting queue to the lock holding queue. When a DDL statement is applied to an MDL lock, because the DDL statement is applied for an exclusive MDL lock, the DML statement acquired at this time needs to apply for the shared-level MDL lock and the exclusive MDL lock applied by the DDL statement to be mutually exclusive. That is, even if the application is successful, the DML statement cannot share the MDL lock with the DML statement. Therefore, the DML statement acquired at this time is added to the lock waiting queue of the MDL. When the DDL statement is executed and exited, the DML statement added to the MDL lock wait queue may be added to the lock holding queue by the lock waiting queue, and if there is a DML statement in the subsequent lock waiting queue, since Apply for a shared-level MDL lock, so they are added to the lock holding queue until the statement that requests the mutual exclusion level MDL lock appears to stop adding.

Further, after the device 1 exits the execution processing of the DDL statement in step S31, when the lock holding queue or the lock waiting queue has a statement corresponding to the exclusive MDL lock, the DML statement is at least One is added to the lock wait queue. When a DDL statement is applied to an MDL lock, because the DDL statement is applied for an exclusive MDL lock, the DML statement acquired at this time needs to apply for the shared-level MDL lock and the exclusive MDL lock applied by the DDL statement to be mutually exclusive. That is, even if the DDL statement is successful, the DML statement cannot share the MDL lock with it. Therefore, the DML statement obtained at this time is added to the MDL lock waiting queue. In the same MDL lock waiting queue, there are other DDL statements for applying the exclusive MDL lock. . When the DDL statement is executed and exited, the DML statement added to the MDL lock wait queue has an exclusive MDL lock in the previous queue, or the current MDL lock holding queue statement holds an exclusive MDL lock. At least one of the MDL statements obtained at this time is added to the lock waiting queue.

It is apparent to those skilled in the art that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the present embodiments are to be considered as illustrative and not restrictive, and the scope of the invention is defined by the appended claims instead All changes in the meaning and scope of equivalent elements are included in the present invention. Any reference signs in the claims should not be construed as limiting the claim. In addition, it is to be understood that the word "comprising" does not exclude other elements or steps. A plurality of units or devices recited in the device claims may also be implemented by a unit or device by software or hardware. The first, second, etc. words are used to denote names and do not denote any particular order.

Claims

A method for processing a DDL statement in a relational database, wherein the method comprises:

Obtaining a DDL statement submitted by the user about the target table, where the DDL statement includes corresponding waiting setting information;

Applying an exclusive MDL lock corresponding to the target table;

If the application for the exclusive MDL lock fails, the exit processing is performed on the DDL statement according to the waiting setting information.
The method of claim 1, wherein the waiting setting information comprises at least one of the following:

Set waiting time;

Zero wait.
The method of claim 2, wherein the wait setting information comprises a set waiting time;

If the step of applying the exclusive MDL lock fails, performing the exit processing on the DDL statement according to the waiting setting information includes:

If the application for the exclusive MDL lock fails, after the waiting time is waited, the exclusive MDL lock is applied again;

If the application for the exclusive MDL lock fails, the execution of the DDL statement is exited.
The method according to claim 2 or 3, wherein said waiting setting information includes zero waiting;

If the step of applying the exclusive MDL lock fails, performing the exit processing on the DDL statement according to the waiting setting information includes:

If the application of the exclusive MDL lock fails, the execution of the DDL statement is exited.
The method according to any one of claims 1 to 4, wherein, if the step of applying the exclusive MDL lock fails, performing the exit processing on the DDL statement according to the waiting setting information comprises:

If the application for the exclusive MDL lock is successful, the DDL statement is executed.
The method according to any one of claims 1 to 5, wherein the step of acquiring a DDL statement submitted by a user regarding a target table, wherein the DDL statement includes corresponding waiting setting information further includes:

Obtaining a DML statement submitted by the user about the target table;

If the step of applying the exclusive MDL lock fails, performing the exit processing on the DDL statement according to the waiting setting information further includes:

After exiting the execution processing of the DDL statement, at least one of the DML statements is added to the lock holding queue or the lock waiting queue of the MDL lock.
The method according to claim 6, wherein said step of adding at least one of said DML statements to said lock holding queue or lock waiting queue of said MDL lock after exiting execution processing of said DDL statement comprises :

After exiting the execution processing of the DDL statement, when the lock holding queue and the statement in the lock waiting queue all correspond to the MDL lock of the sharing level, at least one of the DML statements is added to the The lock holds the queue.
The method according to claim 7, wherein the step of applying for the exclusive MDL lock corresponding to the target table further comprises:

Adding the DML statement to a lock waiting queue of the MDL lock;

The step of adding the at least one of the DML statements to the lock holding queue or the lock waiting queue of the MDL lock after exiting the execution processing of the DDL statement includes:

After exiting the execution processing of the DDL statement, when the lock holding queue and the statement in the lock waiting queue all correspond to the MDL lock of the sharing level, at least one of the DML statements is from the lock A wait queue is added to the lock holding queue.
The method according to any one of claims 6 to 8, wherein said step adds at least one of said DML statements to a lock holding of said MDL lock after exiting execution processing of said DDL statement The queue or lock wait queue includes:

After exiting the execution processing of the DDL statement, when there is a statement corresponding to the exclusive MDL lock in the lock holding queue or the lock waiting queue, at least one of the DML statements is added to the lock waiting queue.
A device for processing DDL statements in a relational database, wherein the device comprises:

a first device, configured to acquire a DDL statement submitted by the user about the target table, where the DDL statement includes corresponding waiting setting information;

a second device, configured to apply for an exclusive MDL lock corresponding to the target table;

And a third device, configured to perform an exit process on the DDL statement according to the waiting setting information if the application for the exclusive MDL lock fails.
The device according to claim 10, wherein said waiting setting information comprises at least one of the following:

Set waiting time;

Zero wait.
The device according to claim 11, wherein said waiting setting information comprises a set waiting time;

Wherein the third device is used to:

If the application for the exclusive MDL lock fails, after the waiting time is waited, the exclusive MDL lock is applied again;

If the application for the exclusive MDL lock fails, the execution of the DDL statement is exited.
The device according to claim 11 or 12, wherein said waiting setting information comprises zero waiting;

Wherein the third device is used to:

If the application of the exclusive MDL lock fails, the execution of the DDL statement is exited.
Apparatus according to any one of claims 10 to 13 wherein said third means is for:

If the application for the exclusive MDL lock is successful, the DDL statement is executed.
The apparatus according to any one of claims 10 to 14, wherein the first device is further configured to:

Obtaining a DML statement submitted by the user about the target table;

The third device further includes:

And a first unit, configured to add at least one of the DML statements to a lock holding queue or a lock waiting queue of the MDL lock after exiting execution processing on the DDL statement.
The apparatus of claim 15 wherein said first unit is for:

After exiting the execution processing of the DDL statement, when the lock holding queue and the statement in the lock waiting queue all correspond to the MDL lock of the sharing level, at least one of the DML statements is added to the The lock holds the queue.
The apparatus of claim 16 wherein said second means is further for:

Adding the DML statement to a lock waiting queue of the MDL lock;

Wherein the first unit is used for:

After exiting the execution processing of the DDL statement, when the lock holding queue and the statement in the lock waiting queue all correspond to the MDL lock of the sharing level, at least one of the DML statements is from the lock A wait queue is added to the lock holding queue.
The apparatus according to any one of claims 15 to 17, wherein the first unit is for:

After exiting the execution processing of the DDL statement, when there is a statement corresponding to the exclusive MDL lock in the lock holding queue or the lock waiting queue, at least one of the DML statements is added to the lock waiting queue.