JPS61127046A - Control system for prefetching from data base - Google Patents

Abstract

PURPOSE:To prevent the useless prefetching actions and to perform only the original data processing job by starting the prefetching control after data satisfying all retrieval conditions are fixed in case the retrieval conditions are formed with combinations of ANDs. CONSTITUTION:The bit map record containing a bit map, an identification code and a record number is written on a main memory 30 with a prefetching controller 20 connected to a central processor 10 and the memory 30. A prefetching control part 21 receives the record numbers to be stored in a page from the processor 10 to send them to an address converting part 24 and at the same time holds the records sent from the memory 30 at a bit map record memory part 22. The bit map is scanned by a prefetching candidate extracting part 23 for acquisition of the first record number coincident with conditions. Then a page number is obtained from said record number through the part 24 and set to a page number register 25. The contents of the register 25 are compared with those of a page number memory part 27 through a prefetched page control part 26. The same processing is repeated with all records coincident with the conditions. The results of these processings are reported to the processor 10.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention Industrial Field of Application The present invention relates to a preemption control method from a database. , data preemption control is often performed. That is, it is checked whether a page containing data that is likely to be accessed in the near future exists in the main memory, and if it does not exist, the absent page is stored in the secondary memory in advance before accessing the main memory. It is transferred in advance from the storage device to the main storage device.

In G-like database systems where the secondary storage device is a database, preemption control from the database is often not performed.

This is because in the case of a database, it is difficult to grasp the clues for preemption, so if you dare to perform preemption control, the processing speed may actually decrease.

On the other hand, in database systems that access data while performing searches, a method is adopted in which preemptive control is performed using the search results as clues.

It is used.

Problems to be Solved by the Invention Conventional database systems that perform preemptive control using search results as clues are configured to perform preemptive control using search results for initial search conditions as clues. Therefore, if the above-mentioned search conditions are composed of a plurality of search conditions (hereinafter referred to as l-compound search conditions J), which are combined by logical product.

Preemptive efforts are often wasted.

In addition, in conventional database systems, the data processing control device performs preemptive control using the first search result as a clue, so there is the problem that this control device cannot concentrate on its primary data processing task. be.

Structure of the Invention In order to solve the problems of the prior art described above, the preemption control method of the present invention is such that when the above search conditions are compound search conditions, the data that satisfies all the search conditions is determined, and then the data is By providing a dedicated prefetch control means for starting prefetch control, the data processing apparatus is configured to prevent wasteful prefetching and to allow the data processing apparatus to concentrate on its original data processing work.

Hereinafter, the operation of the F1 present invention will be explained in detail by way of examples.

Embodiment An information processing system to which a preemption control method according to an embodiment of the present invention is applied is as shown in the configuration block diagram of FIG.
Central processing unit 10 dedicated to data processing, central processing unit 10
Preemption control bag W20. performs preemption control only from the database in parallel with data processing by W20. It is composed of a main storage device 30 and an input/output device 40.

FIG. 2 is a functional block diagram showing an example of the configuration of the preemption control device F 20 shown in FIG. 1 in association with the central processing unit 10 and the main storage device 30. As shown in FIG.

This prefetch control device 20 includes a prefetch control section 21, a bitmap record storage section 22. Preemption candidate extraction unit 23.
Address translation unit 248. Page number register 25. It includes a prefetch page determination section 26 and a page number storage section 27.

The central processing value W10 reads out data matching the search conditions from the main storage device 30 while searching for data, and references it.
Attempts to perform various processing such as modification, addition, deletion, etc. The data search by the central processing unit 10 is performed based on various indexes read in advance from the database into the main memory bag v30.

For example, a database stores employee data consisting of a set of records with fields such as name, age, salary, and place of birth, as shown in Figure 3 (A). It is assumed that index tables (R) and (C) have been created using the respective fields of age and age as keys.

The central processing unit 10 first refers to the index table that has been read into the main storage device 30 from the database in advance, and creates a bitmap that displays the pass/fail of the search results as "1" and "0" for each record in order. Create each condition. For example, when searching for people aged 26 or older whose hometown is Tokyo from among all employees, the central processing unit 10 searches for a bit map B M a related to the hometown, as shown in FIG.
By creating a bitmap BMb related to
Create. In the examples in Figures 3 and 4, the employee record numbers that satisfy the above compound search conditions are record numbers #5 and #8.
It will have the following.

After creating the final bitmap BMf as described above, the central processing unit 1 writes a bitmap record containing this into the main storage device 3. □This bitmap record has a record type identification code TCn, as illustrated in FIG.

The final bit file 18Mf is composed of a corresponding record number 5RNO and a bit map BMf corresponding to the first bit.

The central processing unit 10 is 9. When writing of the bitmap record is completed, the prefetch control unit 21 in the prefetch control device 20 is commanded to start control via the control signal line S1. At the same time, the central processing unit tlO sends the number of records RCP stored in one page to the prefetch control unit 21 via the data line r)1.

The preemption control unit 21, which has received the control start command, activates the bitmap record storage unit 22 via the control signal line S2, and causes bitmap records to be successively output from the main storage device 33 via the data line l')6.

hold it. Further, the prefetch control unit 21 sends the number of records in a page RCP received from the central processing unit 10 to the address conversion unit 24 via the data line D3. When the prefetch control unit 21 receives the notification of completion of bitmap record storage via the control signal line S2, it passes control to the prefetch candidate extraction unit 23 via the control signal line S3.

The prefetch control candidate extraction unit 23 receives the bitmap record from the bitmap record storage unit 22 via the data line D4, and scans the final bitmap RM f bit by bit, thereby extracting the first bit set to “1” ( The relative position of the first record matching the compound search condition by the central processing bag Ff 10 is detected. Subsequently, the preemption control candidate extraction unit 23 adds the detected relative record position and the record number 5RNO of the first record to find the first record number R that matches the compound search condition.
It obtains a NO and passes this to the address conversion section 24.

The address conversion unit 24 divides the record number RNO received from the prefetch control candidate extraction unit by the number of records in a page RCP received from the prefetch control unit 21.
The page number PNO that includes the record is determined and set in the page number register 25. Around this time,
In the segment number field of the page number register 25, the pre-fetch candidate extracting unit 23 sets the record type identification code (TCr) in the bitmap record, that is, the segment number SNO to which the page with the page number PNO belongs.

When the setting to the page number register 25 is completed,
The prefetch control unit 21 activates the prefetch page determination unit via the control signal line S4. The activated pre-fetch page determination unit 26 compares the contents of the page number register 25 and the page number storage unit 27 to extract the page containing the first record that matches the compound search condition from the database into the main storage device F2O. Determine whether the file has already been read. If the page has not yet been read into the main storage device 30, the prefetch page determination unit 26 notifies the central processing gW10 of this via the prefetch control unit 21. Having received this notification, the central processing unit 10 connects the data line D
By reading the contents of the page number register 25 through the input/output device 4, the page number of the prefetch candidate is known.
0 to perform replacement for that page.

If the content of the page number register matches the content of the page number storage unit 27, the prefetch page determination unit notifies the prefetch control unit 21 of this via the control signal line S4.

Upon receiving this notification, the prefetch control unit 21 causes the prefetch candidate extraction unit 23 to start the same process as described above for the next record that matches the composite search condition. In this way,
The above address conversion and determination of existence on the main storage device are repeated for all records that match the composite search condition. The prefetch control unit 21 repeats the above processing for all records that match the compound search condition, and if all the records have already been read into the main storage device f30,
The central processing unit 10 is notified of this fact. The central processing unit 10 that receives this notification knows that there is no need for preemptive control.

The central processing unit 10 updates the contents of the page number storage section 27 via the data line D5 when a change occurs in the page on the storage device 30.

An example of operation when the search condition is a compound search condition has been explained above, but when the search condition consists of a single condition, the bitmap record related to that single search condition is created as in the conventional method. Address conversion and determination similar to those described above are performed sequentially for records set in the bitmap record storage unit 22 in the prefetch control device 20 and in which "1" is set.

Further, the preemption control device 20 is a preemption control unit.

In this example, a configuration is described in which the bitmap record storage unit, prefetch candidate extraction unit, etc. are divided into blocks.

These blocks may be integrated into a suitably sized program, or may be implemented by software or firmware.

Effects of the invention As explained in detail above, 1. When the search condition is a multi-device search condition, the preemption control method of the present invention performs preemption control on the data after the data that satisfies all the search conditions is determined. Since the configuration includes a dedicated prefetch control means for starting the prefetch, it is possible to prevent wasteful prefetching and to reduce the burden of prefetch control on the dedicated data processing device.

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating the configuration of an information processing system to which an embodiment of the present invention is applied, FIG. 2 is a functional block diagram illustrating an example of the configuration of the preemption control device in FIG. 1, and FIG. FIG. 4 is a conceptual diagram illustrating an example of data stored in a database and its index. FIG. 4 is a conceptual diagram illustrating an example of a bitmap created by a search. FIG. 5 is a conceptual diagram illustrating an example of the structure of a bitmap record. . 10...Central processing unit, 20...Preemption control device, 30
...Main storage device, 40...Person output device. 21. Preemption control unit, 22. Bisotoma knob I/
Code storage section, 23... Prefetch candidate extraction section, 24... Address conversion section, 25... Page number register, 26...
Prefetch page determination unit, 27...page number storage unit.

Claims (1)

[Scope of Claim] An information processing system that accesses data that matches a search condition by moving it page by page from a database to a main storage device, the information processing system comprising: 1. A prefetch control method from a database, characterized by comprising a dedicated prefetch control means that starts prefetch control for the data after the data that satisfies all the search conditions has been determined.