JPH03276237A - Inventory updating system - Google Patents

Abstract

PURPOSE:To omit the locking of the inventory records or the inventory pages and to improve the system performance by locking the data pages before the inventory records are updated. CONSTITUTION:An inventory search means 2 searches an inventory area 6 and decides a data page that stores a subject record when the data records are stored. A record store means 1 locks the data page decided by the means 2 and decides whether the relevant record can be stored in the data page or not based on the idle information stored in the data page. If so, the record is stored in the data page and at the same time the idle information included in the data page is updated. If not, the lock state of the data page is canceled and the control is returned to the means 2. Thus it is not required to lock the inventory records or the inventory pages. Then the performance of an inventory updating system is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to database technology, and particularly to an inventory update method for updating an inventory area that manages free space information of data records.

[Conventional technology]

In a database system, in order to prevent frequent input/output to data pages due to space searches when storing records, an inventory area is usually provided that stores free information on data pages as inventory records, and The data page to be stored is determined by performing a search. Incidentally, by storing or deleting a data page, it is necessary to update the inventory record, but conventionally, in order to guarantee the consistency of the inventory record in a simultaneous access environment, it is necessary to update the inventory record in the same way as for the data page. An exclusive lock is placed on the inventory page, or a lock is placed on each inventory record.

[Problem to be solved by the invention]

Conventionally, as described above, locks have been set on inventory pages or inventory records in addition to data pages, which has caused a problem in that the overhead of lock control becomes large. In addition, the locking method for each inventory page that stores multiple inventory records tends to cause waits and deadlocks (and has the problem of reducing system performance).

An object of the present invention is to improve system performance by eliminating the need for locking inventory records or inventory pages.

[Means to solve the problem]

In order to eliminate the need for locking inventory records or inventory pages when storing data pages, the present invention manages free space information of a plurality of data pages as inventory records in the inventory area of the data page, and stores the inventory area in the inventory area when storing data records. In a database system that searches for and determines a data page in which to store the data record, each data page stores free space information of its own page, and when storing a data record, the inventory area is searched and stored. Inventory research means that determines a data page in which a target record is to be stored; and the data page determined by the inventory research means is locked, and the record to be stored can be stored based on free space information included in the locked data page. If it is determined that storage is possible, the record to be stored is stored in the locked data page, and free information in the data page is updated, and if it is determined that storage is not possible, the locked data is stored. record storage means that unlocks a page and returns control to the inventory research means; and an inventory update that updates an inventory record corresponding to the data page in which the record to be stored is stored by the record storage means storing the data record. The means are provided.

Furthermore, in order to eliminate the need for locking inventory pages or inventory records when deleting a data page, the present invention locks the data page containing the record to be deleted when deleting a data record. It has a record deletion means for deleting the target record, and the inventory update means deletes the record to be deleted by the record deletion means to update the inventory record corresponding to the data page that included the record to be deleted. I am trying to update the content.

For C work] Each data page stores its own free space information.

When storing a data record, the inventory research means searches the inventory area and determines the data page in which the record to be stored is stored.

The record storage means locks the data page determined by the inventory research means, and determines whether the record to be stored can be stored in the data page based on free space information contained in the data page.

If it can be stored, the record to be stored is stored in that data page, and the free space information included in that data page is updated. If storage is not possible, the control is returned to the inventory research means after releasing the lock.The inventory update means updates the inventory record corresponding to the data page that stores the record by letting the record storage means store the record. do. Further, when deleting a data record, the record deletion means locks the data page containing the record to be deleted, and deletes the record to be deleted. The inventory update means updates the contents of the inventory record corresponding to the data page that included the record to be deleted by the record deletion means to delete the record to be deleted.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, which includes a record storage means 1, an inventory research means 2, an inventory update means 3, a record deletion means 4, and a database 5 including an inventory area 6 and a data area 7. It consists of In addition, in the same figure, the dotted line and solid line arrows respectively indicate control.

Shows the flow of data.

As shown in FIG. 2, the inventory area 6 in the database 5 includes a plurality of inventory pages 6-1, 6-2.・
Consisting of ..., each inventory page 6-1.6-
2. ... stores a plurality of inventory records, respectively. Furthermore, the data area 7 in the database 5 has a plurality of data pages, as shown in FIG. -1,7-
2,...? -i.

..., and each data page 7-1.7-2゜..., 7-i+ ... has free space information indicating the size of the free space of its own page in the header section.This free space information is It is also managed as an inventory record. That is, the i-th data page in the data area 7? -Free space information of i is the i-th inventory record in inventory area 6 #
managed as i.

Record storage means 1. The record deletion means 4 stores and deletes data records in the data area 7, respectively. Inventory research means 2 is record storage means 1
, the inventory area 6 is searched and a data page with sufficient free space is identified. The inventory update means 3 is called by the record storage means I and the record deletion means 4, and reflects the changed data page free space information in the inventory area 6.

3 and 4 are flowcharts showing processing examples of the record storage means 1 and the record deletion means 4, respectively, and the operation of this embodiment will be explained below with reference to each figure.

As shown in FIG. 3, the record storage means 1 first determines the home page which is the data page in which the data record is to be stored (step 3301), and then starts the event research means 2 and enters the home page number and the record to be stored. The record size is passed to the inventory research means 2 (step 5302).

As a result, the inventory research means 2 starts searching from the inventory record corresponding to the home page number, and specifies a data page number with sufficient free space to store the data record.

This search is performed by reading the inventory page without locking it. When the data page number is specified, the inventory research means 2 passes the specified data page number to the record storage means 1 and returns control to the record storage means 1.

When the data page number is passed, the record storage means 1 stores the corresponding data page (data page to be stored).
Locks the page in exclusive mode and reads the page (
Step 5303). However, if the task is locked by another task, the same process will be performed after waiting for the lock to be released. Next, the size of the free space indicated by the free space information stored in the header section of the read data page is compared with the data record size to be stored, and it is re-determined whether the data record can be stored (step 33
04).

If it is determined that storage is not possible, the data page is unlocked (step 305), the homepage is set as the next data page (step 5306), and step 302
Re-execute the process from If it is determined that the page can be stored, a data record is written to that page, and the free space information stored in the header section is updated to a value obtained by subtracting the data record size from the original value (step 53).
07), when the process of step 307 is completed, the record storage means 1 activates the inventory update means 3, and passes the data page number in which the data record is stored and the updated free information to the inventory update means 3 (step 33).
08).

As a result, the inventory update means 3 reads the inventory page including the inventory record corresponding to the data page number without locking it, writes new free information to the corresponding inventory record, and returns control to the calling record storage means 1.

When the record storage means 1 is returned control, it ends its processing. Note that the data page locked in step 303 is unlocked by a command.

Next, the operation when deleting a data record will be explained.

As shown in the flowchart of FIG. 4, the record deletion means 4 determines the data page containing the data record to be deleted (step 5401), locks the data page in exclusive mode, and reads it (step 5402).
However, if the above data page is locked by another task, wait for the lock to be released and perform the same process. Next, delete the data record from the above data page and store it in the header section of that data page. The free space information that has been deleted is increased by the size of the deleted data record (step 5403), and then the inventory update means 3 is activated to update the inventory with the number of the data page from which the data record was deleted and the updated free space information. It is passed to means 3 (step 5404).

As a result, the inventory updating means 3 performs the same process as when called by the record storage means I, and sets the contents of the corresponding inventory record as new free information. At that time, no lock is set on the inventory page. After updating the contents of the inventory record, the inventory update means 3 returns control to the record deletion means 4.

When the control is returned, the record deletion means 4 ends its processing. Note that the data page locked in step 402 is unlocked by a commit instruction.

As mentioned above, in both record storage processing and record deletion processing that involve inventory record updating processing, the inventory record updating processing is performed after the data page is locked in exclusive mode.
Even when multiple tasks accessing the database coexist, the inventory records are updated sequentially and in a mutually exclusive manner, making it possible to maintain the consistency of the inventory records. In addition, a data page determined to be storable by searching the inventory area 6 without locking when storing a data record is updated by another task before being locked in step 303 of FIG. 3, and becomes unstorable. However, by re-determining after locking in step 304, it is possible to detect that storage is not possible, and the data record can be stored in another data page.

〔Effect of the invention〕

As explained above, the present invention guarantees the consistency of inventory records by reading the data page prior to updating the inventory records without locking the inventory pages or inventory records. Since inventory is not locked, overhead is reduced, unnecessary page waits and deadlocks are eliminated, and system performance can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing an example of the configuration of an inventory area and a data area, FIG. 3 is a flowchart showing an example of processing by the record storage means, and FIG. 4 is a record deletion 3 is a flowchart illustrating an example of processing by the means. In the figure, 1... Record storage means, 2... Inventory research means, 3... Inventory update means,
4... Record deletion means, 5... Data hash, 6
...Inventory area, 7...Data area.

Claims (2)

[Claims] (1) In a database system that manages free space information of a plurality of data pages as inventory records in an inventory area in a database, and when storing a data record, searches the inventory area to determine the data page in which the data record is to be stored. an inventory research means for storing free space information of its own page in each data page, and searching the inventory area to determine a data page in which to store a record when storing a data record, and the inventory research means locks the determined data page, determines whether or not the storage target record can be stored based on the free space information included in the locked data page, and determines that the storage target record can be stored. record storage means that stores in the locked data page and updates free information in the data page, releases the lock on the locked data page by determining that storage is impossible, and returns control to the inventory research means; An inventory update method comprising: an inventory update unit for updating an inventory record corresponding to a data page in which the record to be stored is stored by the record storage unit storing the data record. (2) When deleting a data record, the record deleting means locks a data page that includes a record to be deleted and deletes the record to be deleted, and the inventory updating means includes the record deleting means. 2. The inventory update method according to claim 1, wherein by deleting the record to be deleted, the content of an inventory record corresponding to a data page that included the record to be deleted is updated.