KR20180054423A - Method and apparatus for journaling of file-based database which is used by one application - Google Patents

Abstract

Disclosed is a method of journaling a file-based database used by a single application. According to an embodiment of the present invention, the method of journaling a database copied from an original database used by a single application includes: a step of applying a change of the original database, made by the single application, to the copied database; a step of generating a second original database and a second copied database by switching the original database and the copied database; and a step of writing completion information, which indicates that the copied database has been completely changed, in the second copied database.

Description

METHOD AND APPARATUS FOR JOURNALING OF FILE-BASED DATABASE WHICH IS USED BY ONE APPLICATION FIELD OF THE INVENTION [0001]

The present invention relates to a journaling method and apparatus for a file-based database used by a single application, and more particularly, to a journaling method and apparatus using an original database used by a single application and a replicated database replicating the original database.

The database employs a data journaling scheme to ensure the integrity of the data. SQLite, one of the mobile databases, provides PERSIST and WAL modes for journaling, and DELETE, TRUNCATE, MEMORY and NONE modes are provided as default. PERSIST mode guarantees integrity by writing the data in the database to the journal file before changing it, but you should use heavy system calls (eg fdatasync) frequently. In the DELETE and TRUNCATE modes, there are differences in creation / deletion of journal files. MEMORY and NONE modes do not guarantee data integrity. WAL mode is faster and lighter than writing directly to a data file, since it appends updates to the end of the journal file.

However, while SQLite's journal mode has the advantage that WAL is efficient for write requests, there is a disadvantage that the read request must be processed by referring to the current log file and data file. Also, when used with EXT4 in mobile environment, additional I / O performance drops due to design problems. PERSIST mode requires a total of five system calls per transaction, which is a factor in overall database performance degradation.

Accordingly, there is a need for a journaling method and an apparatus having excellent performance that does not deteriorate the performance of a mobile system while adopting a data journaling scheme for a file-based database used by a single application.

Related Prior Art Korean Patent Registration No. 10-1258589 entitled " Information Storage Medium in which Data is Recorded According to a Journaling File System, Method and Apparatus for Recording / Restoring Data Using a Journaling File System, May 2, 2013).

An object of the present invention is to provide a journaling method and apparatus that can be applied to a file-based database used by a single application and can guarantee the integrity of data by supporting a journaling function with a small reduction in performance.

The problems to be solved by the present invention are not limited to the above-mentioned problem (s), and another problem (s) not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a journaling method for a file-based database used by a single application provided in the present invention, the method comprising: journaling a database using a replicated database replicating an original database used by a single application, Reflecting the change of the original database in the replica database; Generating a second original database and a second replicated database by interchanging the original database and the replica database; And recording completion information, which is information indicating that the change of the original database is completed, in the second replica database.

Preferably, before the step of creating the second replica database, the step of updating the replica database may further include the step of updating the replica information according to a predetermined criterion.

Preferably, the step of recording the completion information may record the completion information by initializing and recording the change information.

Preferably, when the change information includes a status value indicating a change status of the database, the change information of the duplicate database is updated to include a status value that is larger than the change information of the original database by a predetermined size, 2 The status value included in the change information of the duplicate database can be initialized to a predetermined initial value.

Preferably, a synchronization function, which is a function synchronizing the change of the original database or the replica database file with the storage device, may be called in correspondence with each of the steps of reflecting on the replica database and recording the completion information.

In order to solve the above problems, a journaling apparatus of a file-based database used by a single application provided in the present invention is an apparatus for journaling a database using a replicated database replicating an original database used by a single application, A file update unit for reflecting a change of the original database by a single application to the replica database; And a file exchange unit for exchanging the original database and the replica database to generate a second original database and a second replica database, wherein the file renewing unit updates the original database to the second replica database The completion information is recorded.

Preferably, the file updating unit may further update the change information, which is information indicating a change state of the database, to the replica database according to a predetermined criterion.

Preferably, the file updating unit may record the completion information by initializing and recording the change information.

Preferably, when the change information includes a status value indicating a change status of the database, the change information of the duplicate database is updated to include a status value that is larger than the change information of the original database by a predetermined size, 2 The status value included in the change information of the duplicate database can be initialized to a predetermined initial value.

Preferably, the synchronizing function, which is a function of synchronizing the original database or the replica database file with the storage device, is performed when the file updater reflects a change of the original database to the replica database, And can be called when creating the original database and the second replica database, respectively.

The details of other embodiments are included in the detailed description and the accompanying drawings.

The present invention introduces a journaling mode using a source database and a duplicate database replicating the source database with respect to a file-based database used by a single application, thereby ensuring data integrity while preventing performance degradation.

In addition, by minimizing I / O of a file by using a feature that a single application uses a file-based database, it is possible to prevent degradation of database performance.

FIG. 1 is a flowchart illustrating a journaling method of a file-based database used by a single application according to an embodiment of the present invention.
2 is a flowchart illustrating a journaling method of a file-based database used by a single application according to another embodiment of the present invention.
3 is a diagram for explaining a file-based database journaling apparatus used by a single application according to an embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

The terms first, second, A, B, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a flowchart illustrating a journaling method of a file-based database used by a single application according to an embodiment of the present invention.

A journaling file system is a file system that can maintain the integrity of a disk in the event of a system crash or power outage. More specifically, when a conflict occurs while keeping all the contents of the data area of the disk in a log, the metadata in the log re-creates the lost data to return the data before the crash, .

The present invention relates to a journaling method and apparatus, such as a journaling file system, that enables a database to be recovered in the event of a system conflict or a power outage for a file-based database. The journaling method and apparatus of the present invention can be applied to or installed in a smart phone, a mobile device, a tablet device, and a wearable device based on Android, iOS, or other OS. May be applied or mounted on a computer device.

More specifically, the journaling method and apparatus of the present invention can operate in such a manner that changes to be applied to the original database are recorded in the replica database, and the original database and the replica database are exchanged when the recording is completed. At this time, each of the original database and the replica database may include change information, which is information indicating a change state of the database, and this change state can be represented by a state value.

For example, the state values of the original database and the replica database may initially be < n, 0 >. Then, the state value can be <n, n + 1> when the record of the changes to the replicate database is completed (that is, the transaction is completed). Then, the state value can be <n + 1, n> after exchanging the files corresponding to the original database and the replicated database. Finally, the state value of the new second original database (existing replica database) and the second replica database replicating the second original database becomes < n + 1, 0 >, and journaling can be performed again. Meanwhile, the journaling method of the present invention described above can be called a SHADOW mode.

In step S110, the database journaling apparatus reflects the change of the original database by the single application to the replica database.

At this time, the database journaling device can assume that the source database and the replicate database are used only by a single application. Therefore, the single application can use the database at any time, if necessary, without having to use the database while locking and unlocking as in the case of a plurality of applications using the database.

In other words, changes made by the database journaling device to the original database can be reflected in the replicated database.

In step S120, the database journaling apparatus switches the original database and the replica database to create a second original database and a second replica database.

For example, the database journaling device may change the name of the shadow database file to create a second source database file, and change the name of the file in the database file to create a second replica database file .

Finally, in step S130, the database journaling apparatus records completion information, which is information indicating that the change of the original database has been completed, to the second replica database.

That is, the database journaling device may record completion information in the second replica database file indicating that at least one transaction involved in the change by the single application has been completed. The database journaling apparatus can determine whether the application of the change by the single application has been completed according to whether the completion information is recorded in the newly created second replica database file.

In another embodiment, a synchronization function may be invoked corresponding to steps S110 and S130, respectively, which is a function to synchronize changes in the original database or replica database file with the storage device.

For example, if the database journaling device is based on Linux or Unix, the synchronization function may be the fdatasync () function, and the fdatasync () function is called once every time each of steps S110 and S130 is performed, Compared with the conventional technology (SQLite), which is called and called 5 times, file I / O can be reduced.

As described above, the journaling method of a file-based database used by a single application according to an embodiment of the present invention introduces a journaling mode using a source database and a duplicate database in which the original database is duplicated, It is possible to prevent deterioration in performance.

2 is a flowchart illustrating a journaling method of a file-based database used by a single application according to another embodiment of the present invention.

In step S210, the database journaling apparatus reflects the change of the original database by the single application to the duplicate database.

In step S220, the database journaling apparatus updates the change information, which is information indicating the change state of the database, to the replica database according to a predetermined criterion.

For example, the database journaling apparatus can access the original database and the replica database, which are file-based databases, and record change information, which is information on the changed state of each of the original database and the replica database, according to a predetermined criterion. That is, the database journaling device may update the change information to indicate that the change in the original database is reflected in the replicate database.

More specifically, in order to update the change information, the database journaling apparatus can update the change count value existing in the header of the database file by adding a value of a certain size (e.g., +1). In this manner, when the database journaling device updates the change information in the database file, when the system collision and the power supply interruption occur in the future, the change information can be used to recover the database.

Since the database journaling device can assume that the original database and the replica database are used only by a single application, after performing steps S210 and S220, by synchronizing the changes of the steps S210 and S220 to the storage device only once, It is possible to minimize deterioration of system performance due to frequent execution of file I / O. On the other hand, steps S210 and S220 may be performed by changing the order thereof as necessary.

In step S230, the database journaling apparatus switches the original database and the replica database to create a second original database and a second replica database.

Finally, in step S240, the database journaling apparatus records completion information, which is information indicating that the change of the original database has been completed, to the second replica database.

In another embodiment, the database journaling device may initialize and record the change information, thereby recording the completion information.

For example, the database journaling apparatus can record the completion information by initializing and recording the change status value present in the header of the database file to zero. That is, the database journaling device can regard the completion information as being recorded in the database file when the change state value is stored as 0.

In another embodiment, when the change information includes a status value indicating a change status of the database, the change information of the duplicate database is updated to include a status value larger by a predetermined size than the change information of the original database, The state value included in the change information of the database may be initialized to a predetermined initial value.

For example, if a change to the original database whose change status value is n in the header of the database file is reflected in the duplicate database, the change status value of the duplicate database can be incremented by n + 1 by one.

When the replacement of the original database and the replicated database is completed and a second original database and a second replicated database replicating the second original database are created, the changed status value existing in the header of the second replicated database file is set to 0 And can indicate that the journaling can be performed again

3 is a diagram for explaining a file-based database journaling apparatus used by a single application according to an embodiment of the present invention.

Referring to FIG. 3, a file-based database journaling apparatus 300 used by a single application according to an embodiment of the present invention includes a file updating unit 310 and a file exchanging unit 320.

The file update unit 310 reflects the change of the original database by the single application to the duplicate database.

The file exchange unit 320 switches the original database and the replica database to create a second original database and a second replica database.

At this time, the file update unit 310 may further record the completion information, which is information indicating that the change of the original database is completed, in the second replica database.

In another embodiment, the file update unit 310 may record the completion information by initializing and recording the change information.

In another embodiment, when the change information includes a status value indicating a change status of the database, the change information of the duplicate database is updated to include a status value larger by a predetermined size than the change information of the original database, The state value included in the change information of the database may be initialized to a predetermined initial value.

In another embodiment, a synchronization function, which is a function for synchronizing a change of an original database or a replica database file with a storage device, is performed when the file updater 310 reflects a change of the original database to the replica database, Can be called when creating the second original database and the second replicated database, respectively.

The above-described embodiments of the present invention can be embodied in a general-purpose digital computer that can be embodied as a program that can be executed by a computer and operates the program using a computer-readable recording medium.

The computer readable recording medium includes a magnetic storage medium (e.g., ROM, floppy disk, hard disk, etc.), optical reading medium (e.g., CD ROM, DVD, etc.).

The present invention has been described with reference to the preferred embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims (10)

A method for journaling a database using a replicated database replicating an original database used by a single application,
Reflecting the change of the original database by the single application to the replica database;
Generating a second original database and a second replicated database by interchanging the original database and the replica database; And
Recording completion information, which is information indicating that the change of the original database is completed, in the second replica database
Based database that is used by a single application. The method according to claim 1,
Prior to the step of creating the second replica database,
Updating the change information, which is information indicating a change state of the database, to the replica database according to a predetermined criterion
Further comprising the steps of: (a) receiving a journaling request for a file-based database; 3. The method of claim 2,
The step of recording the completion information
Wherein the change information is initialized and recorded so that the completion information is recorded. A method of journaling a file-based database used by a single application. The method of claim 3,
When the change information includes a status value indicating a change status of the database,
The change information of the replica database is updated to include a state value that is larger than the change information of the original database by a predetermined size,
Wherein the state value included in the change information of the second replica database is initialized to a predetermined initial value. The method according to claim 1,
Wherein the synchronization function is a function for synchronizing the change of the original database or the replica database file with the storage device
The step of reflecting on the replica database, and the step of recording the completion information are called in correspondence with each other. 1. An apparatus for journalizing a database using a replicated database replicating an original database used by a single application,
A file updating unit for reflecting the change of the original database by the single application to the replica database; And
A file exchange unit for creating a second original database and a second replica database by switching the original database and the replica database,
Lt; / RTI &gt;
The file update unit
Wherein the completion information is information indicating that the change of the original database is completed in the second replica database. The method according to claim 6,
The file update unit
Wherein the change information, which is information indicating a change state of the database, is further updated with respect to the replica database according to a predetermined criterion. 8. The method of claim 7,
The file update unit
Wherein the change information is initialized and recorded so that the completion information is recorded. 9. The method of claim 8,
When the change information includes a status value indicating a change status of the database,
The change information of the replica database is updated to include a state value that is larger than the change information of the original database by a predetermined size,
Wherein the state value included in the change information of the second replica database is initialized to a predetermined initial value. The method according to claim 6,
Wherein the synchronization function is a function for synchronizing the change of the original database or the replica database file with the storage device
When the file update unit reflects the change of the original database in the replica database and when the file exchange unit creates the second original database and the second replica database, The journaling device in the database.

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