JPH01237853A - System for processing degeneration of prime page in hash file - Google Patents

Abstract

PURPOSE:To efficiently perform the degeneration processing of a prime page and to reduce a load on the processing by changing an overflow page itself to the prime page on a buffer when a vacant prime page is generated. CONSTITUTION:A prime page degeneration processing part 19 checks whether or not the prime page P0 in a buffer area B0 is completely vacant when the record on the prime page P0 in the buffer area B0. When it is detected that the prime page is vacant, it is checked whether or not the overflow page exists on the next page list. When it exists, the page id 14 of a leading overflow page P1 is changed to the page id 13 on the prime page P0. In other words, the overflow page P1 in a buffer area B1 becomes the prime page P0, thereby, the degeneration processing can be performed without moving the record between the pages.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a file management method using the hash method in a data processing system.

The purpose is to improve the efficiency of prime page degeneration processing and reduce the processing burden.

When a prime page becomes vacant, the page identification information of the overflow page is replaced with the page identification information of the prime page, and writing to an external storage medium is performed from the overflow page with the page identification information replaced.

[Industrial application field]

The present invention relates to a file management method using a hash method in a data processing system.

The hash method is one way to avoid a drop in file storage efficiency when the keys of a record are extremely sparsely distributed in the key space.It applies a hash function to the keys and distributes them more densely. Convert it to a value in the Hanosh function space to determine the target page for record operations. A file of this type is called a hash file.

The hash function is a pseudo-random function, so multiple different record keys may be converted to the same hash value. Therefore, only one page is determined in direct association with the hash value, and a plurality of records can be stored in that page. When that page runs out of space, other pages can be linked and used.

The page determined by this hash value is a specific page within the file, and this page is called a prime page. Pages other than prime pages are called overflow pages. In this file, in order to determine the target page, a list (hereinafter referred to as a page list) connected from the prime page is determined using a hash.

It is possible to limit the search range and increase search efficiency until reaching the target page.

The present invention particularly relates to a process for degenerating a prime page when the page list has one or more overflow pages and the prime page becomes vacant due to record deletion.

[Conventional technology]

FIG. 3 shows the basic configuration of a conventional hash file.

In FIG. 3, l is a hash file, 2-0 to 2-n are prime pages, 3 is an overflow page of prime page 2-2, 4-0 to 4-3 are empty overflow pages, and 5-0 to 2-n are empty overflow pages. 5-4 is a record, 6.
7 is page id, Ha, which indicates the physical location of the page;
H+, Hz,...

H7 represents the hash value.

In such a hash file, when the page list (including only prime pages) becomes full by storing records, unused overflow pages are acquired and the list is sequentially updated. Make it grow.

However, in general, as the page list grows in a hash file, more free space becomes available due to record deletion.

There is a problem in that it leads to a decrease in search efficiency. Therefore, in order to improve search efficiency, it is necessary to store records at the beginning of the page list or to suppress the growth of the page list.

As one of the ways to suppress the growth of page list.

There is a page list degeneracy process. Furthermore, this is divided into degeneration processing when the prime page becomes free and degeneration processing when the overflow page becomes free.

In the latter case, the overflow page that is no longer needed can be removed from the list and left unused. However, in the former case, the prime page is a page selected based on the H.7 value.

It cannot simply be separated from the page list.

Hereinafter, a page that becomes free due to record deletion processing will be referred to as a reduced page. If the reduced page is an overflow page, it will be removed from the page list and managed as a free page. Therefore, when an overflow page exists in the page list, one or more records always exist within that page.

If there are no records in the prime page due to record deletion and an overflow page exists,
In order to improve search efficiency, records in the overflow page are moved to the prime page, and the overflow page that becomes vacant due to the move is returned. This is the prime page degeneration process.

A conventional prime page degeneracy processing method will be explained using FIG. 4. Note that the reference numbers in the figures are those in FIG. 3. However, an external storage medium 8 with an overflow page 3'' is newly added.

(1) Record movement It is assumed that records 5-0 to 5-3 of Niblime page 2-2 have been deleted and are now empty. Therefore, record 5-4 of overflow page 3 connected immediately after prime page 2-2 is moved to prime page 2-2.

(II) Updating the Page List The overflow page 3, which has become vacant due to the movement of the record 5-4, is separated from the page list. That is, the link from prime page 2-2 is cut off and returned to the pool of free overflow pages. Note that if another overflow page 3 is linked after the overflow page 3 as shown in Figure 2, the link is changed from the prime page to that page.

(If) Reflection on media: The updated contents of Prime Page 2-2.

Write to external storage medium 8.

[Problem to be solved by the invention]

In the conventional method, records are moved from the overflow page when performing prime page degeneration processing, but
If the page length of the overflow page is long (several KB to several tens of KB) and there are many records to be transferred, the processing load for record transfer becomes heavy, and after the records are transferred to the prime page, it is necessary to transfer the records to the prime page again. Since the data is written to a medium, the process takes time and reduces system efficiency.

The present invention aims to improve the efficiency of prime page degeneration processing,
The purpose is to reduce the processing burden.

[Means to solve the problem]

This invention works when a prime page becomes vacant.

Instead of moving the record of the immediately following overflow page to the prime page, the overflow page itself is changed to a prime page on the buffer, and the reflection on the external storage medium is written directly from this changed prime page to the medium. This eliminates the need for record movement.

FIG. 1 is a diagram explaining the principle of the present invention.

In Figure 1.

9 is the main memory.

10 is a buffer area B0 of the prime page P0.

11 and 12 are respective buffer areas B+ of overflow pages P+ and Pg linked to prime page P0,
It is Bz.

13 to 15 are page IDs (page identification information!1).

16-1 to 16-3 are records.

17 is an external storage medium.

18 is a prime page P0 storage area.

Reference numeral 19 denotes a prime page degeneration processing unit, which processes page 1d14 of overflow page P1 in buffer area B1 during prime page degeneration processing.

Page L of prime page P0 in buffer area B0
d13, and a function 19b that writes the contents of the buffer area B1 to the prime page P0 storage area of the external storage medium 17 in response to an instruction to write to a prime page medium specifying pages Po and P+. .

[Effect]

In FIG. 1, the prime page degeneration processing unit 19 determines whether prime page P0 in buffer area B has become completely empty when the record of prime page P0 in buffer area B0 is deleted or at any other appropriate timing. Find out if.

When it is detected that the prime page P is empty, it is first checked whether there is an overflow page in the page list.

If there is no overflow page, the empty prime page is written as is, and if there is an overflow page, page 1d14 of the first overflow page P1
is changed to page 1d13 of prime page P0. That is, the overflow page P of the buffer area B1 becomes the prime page P0.

Next, prime page P0 in buffer area B1.

It is written to the prime page P0 storage area 18 of the external storage medium 17, and the buffer area B0 is made invalid.

In this way, it is possible to simply perform degeneracy of two prime pages without moving records between pages.

〔Example〕

Next, the present invention will be explained in detail with reference to Examples.

In order to transfer records and reflect Prime Page on media all at once, consider the following points.

(1) Unify the format of prime pages and overflow pages.

As a result, the only thing that distinguishes a prime page from an overflow page is the page management information written within the page. As a result.

By simply changing this information on the buffer, it is possible to change the prime page and overflow page.

Note that the page management information referred to here refers to information about the page itself such as the page position within the file and the page list, and does not refer to management information such as records within the page.

(2) Eliminate physical information from within the page.

Logical location information within the page (serial number from the beginning)
By having only the page management information, it becomes possible to easily change the page management information. This location information is also used as a page ID.

(3) Provide a function that integrates record transfer and page export and converts it to export to another page.

By specifying two (D page'; (Pa, P+), the contents of buffer area B1 corresponding to page P (changed to correspond to Po) are transferred to page P on the medium.
6 Create a function that performs the process of writing to the storage area. This makes it possible to convert a two-step process of record movement and subsequent writing into a one-step process of writing directly onto the medium.

FIG. 2 shows the logical structure of a hash file according to one embodiment of the present invention.

In FIG. 2, prime pages are assigned location information #0 to #n corresponding to page IDs, and overflow pages are assigned #n+1 to #m, and 9 location information is greater than or smaller than n. The type of page can be identified by the type of page.

In addition, a space management record of location information #α is provided to manage empty pages.

Prime pages and overflow pages.

Each has a record storage area and a page management information area.

The page management information includes the above-described location information and page list information, that is, a pointer indicating an overflow page linked to the prime page or another overflow page linked to the overflow page.

In the replacement of an overflow page with a prime page according to the present invention, an overflow page having one location information within the range of #n+1 to #m is replaced with a prime page from #0 to #n.
This means that the location information is replaced with one corresponding piece of location information within the range of .

These positional information are uniquely associated with the buffer area of the main memory. In the illustrated example, the buffer area management table fulfills this function.

Therefore, changing one position information causes a change in correspondence with the buffer area, and the same effect as record movement can be obtained.

For example, when the location information of prime page P0 explained in FIG. , invalidate page P of the buffer area management table, and replace page P with
Sofa B of No. 1 is associated with PO (#k) on the medium.

Therefore, specifying prime page B and instructing it to be written to a medium is equivalent to writing out the contents of overflow page P and moving the record.

〔Effect of the invention〕

According to the present invention, there is no need to move records, which was conventionally required in prime page degeneration processing.

The processing time is significantly reduced and the processing efficiency of the system is also improved.

[Brief explanation of the drawing]

Figure 1 is a diagram explaining the principle of the present invention, Figure 2 is a logical configuration diagram of a hash file according to an embodiment of the present invention, Figure 3 is a basic configuration diagram of a conventional hash file, and Figure 4 is a conventional prime page diagram. FIG. 2 is an explanatory diagram of a degeneracy processing method. In Figure 1. 10 Niblime page P0 buffer GM area B. 11 Buffer area B+ of Nioh flow page P1 12 Buffer area 13 to 1 of Nioh flow page P2
5; Page ID (page identification information) 16-1 to 16-3
Ni record 17: External storage medium 18 Niblime page Po storage area 19 Niblime page degeneration processing unit

Claims (1)

[Claims] In a data processing system equipped with a hash file in a format that stores records using a prime page and an overflow page when necessary, when the prime page (P_0) becomes free, the overflow page is used to store records. record transfer in memory,
The page identification information of the overflow page (P_1) is directly replaced with the page identification information of the prime page, and writing to the external storage medium (17) is performed from the overflow page (P_1) in which the page identification information has been replaced. Prime page degeneration processing method for hash files.