JP2540821B2 - Database search system - Google Patents

Description

The present invention relates to a database system of an electronic computer,
In particular, it relates to index search control.

(Prior Art) With the development of information processing using electronic computers, commonization of data files referred to by business programs that perform data processing is progressing.

For example, in the case of a typical example in a company, information about an individual such as employee number, name, work history, and affiliation is referred to and updated in payroll calculation, and employee number, name, anamnesis, and family are included in welfare management. Refer to and update information such as (unmarried, married) and dependents.

It is hoped that these information will not be duplicated for each business program, but shared as a source file, efficiently maintained, and accessed at high speed from the basics of a database system (Shunsuke Uemura, Ohmsha, Showa 58
Page 17 lines 16 to 20 defines the database system as follows.

"What is a database system?
A system that collectively controls data related to a single organization such as a company, a university, a hospital, or a government office, and allows multiple types of users to share the data. The data is integrated with the least amount of redundancy to form a database, which users share in a way that is convenient for their business.
However, even if the user's point of view of the database is different, the method of operating the database is unified and centrally controlled. The amount of data shared as a database will be large, and high-speed means will be required to retrieve the desired data. An index is a general high-speed access method for a database. Page 124, lines 1 to 3 of "Database Management (James Martin, Computer Society of Japan, published in 1982)" defines the index as follows.

“An index is a table that works with a procedure that accepts as input information about certain attribute values and provides as output information that helps to quickly locate the record (s) with these attribute values. Can be defined as Conventionally, the index is searched by sequentially searching from the information record regarding the index or the highest level block of the index, and searching the lowest level index block including the desired index.

The highest level block and the lowest level block are input by reading from the auxiliary storage device storing the database file into the main storage device in block units. The address at which the requested block is read into the main memory is returned to the requester of these blocks.

"Design and development of database system (Amimura, Yamada,
Horiuchi, Ohmsha, published in 1983) ”introduces a method for efficiently inputting a database file to a large-capacity auxiliary storage device by using a specific area on the main storage ( Page 195, right column, line 9 from bottom to page 196, left column, line 6).

“When reading a CI from a magnetic disk through a channel, if there is no buffer area on the main memory,
I / O command (EXCP) cannot be issued. Also, I
Check the database buffer for the requested data before issuing the / O instruction. This method is called the look-aside buffer method, and is used to unconditionally
Indicates that the I / O instruction is not issued in synchronization with the O request. If there is no free buffer in the database buffer pool, the oldest buffer content that may be written to the external magnetic disk is written. This method uses the same LRU (L
east recently use) standard. The CI in the above description is an abbreviation for CONTROL INTERVAL and is synonymous with the block in the present invention.

FIG. 4 is a block configuration diagram for realizing the index search method according to the conventional technique. In FIG. 4, 41 is an index retrieval means, 42 is an index information record reference means, 43 is an upper level index retrieval means, 44 is a lowest level index retrieval means, 45 is a main storage device, 46 is an upper level index block, and 47 is The lowest level index block, 48 is auxiliary storage.

In FIG. 4, the index search means 41 is composed of index information record reference means 42, upper level search means 43, and lowest level index search means 44. Also, the main memory 45
Consists of an upper level index block and a lower level index block.

FIG. 5 is an explanatory diagram showing a conventional indexing method. In FIG. 5, 51 is an index key information record, 52 is the highest level index block, 53 is the lowest level index block, 54 is the upper level index key, 55 is the lowest level index key, and 56 is the lowest level index key. Is.

In FIG. 5, the index is an index key information record 51,
It consists of a top level index block 52 which stores a top level index key 54 and a bottom level index block 53 which stores a bottom level index key 55 or a bottom level index key 56.

Next, a specific example of the conventional technique will be described with reference to FIGS. 4 and 5.

First, the index search means 41 is an index information record reference means.
Request 42 the block number of the highest level index block.

Secondly, the upper level index search means 43 inputs the upper level index block by the index information record reference means 42 or the block number obtained by the upper level index search means 43 to input the corresponding upper index key. Explore.

Thirdly, if the upper level index key retrieved by the upper level index retrieval means 43 points to the upper level index block, the control is passed to the upper level index retrieval means 43 again, and the control from the second step is started. Repeat the process.
If the retrieved upper level index key points to the lowest level index block, the control is passed to the lowest level search means 44.

Fourth, the lowest level search means 44 inputs the lowest level index block according to the lowest level index block number obtained by the higher level index search means 43, and enters the corresponding lowest level index key. Do a search.

In FIG. 5, assuming the process of directly reading the lowest level index key 55 and reading from the lowest level index key 55 in ascending order of the keys, the following process is performed until the lowest level index key 56 is searched. . That is, first to look up the index information record 51 to search for the lowest level index key 55, and secondly to search for the upper level index key 54,
Third, the lowest level index key 55 is searched. In order to search the lowest level index key 56, firstly, the index information record 51 is referred to, secondly, the upper level index key 54 is searched, and thirdly, the lowest level index key 55 is searched. Then, fourthly, the lowest level index key 56 corresponding to the ascending order of the lowest level index key 55 is searched.

FIG. 6 illustrates the upper level index key and the lower level index key in a general index. Both the upper level index key and the lower level index key consist of an index key value and a pointer value.

The index key value is a specific item or a plurality of items included in the record. For example, when an employee record is assumed, if a search by name is performed, the item and name on the employee record are used as the index key value. The pointer value is different from the upper level index key and the lower level index key. The pointer value of the higher level index key stores the block number on the secondary storage device of the lower level index block managed by the higher level index key. The index key value of the upper level index key is the upper level index key included in the lower level index block or the index key value having the largest value among the lowest level index keys.

On the other hand, the pointer value of the lowest level index key has the address on the secondary storage device of the record equal to the lowest level index key, usually the block number and the in-block address.

(Problems to be Solved by the Invention) In the above-described conventional method, the processes required for searching the lowest level index key searched immediately before are duplicated. That is,
In the above-mentioned conventional technique, the process of referring to the index information record 51, the process of searching the upper level index key 54, and the process of searching the lowest level index key 55 are repeated. As a result, it takes a long time to search for the target lowest level index key 56.

An object of the present invention is to provide a database search system configured to eliminate the above-mentioned drawback by storing the lowest level index block including the lowest level index key searched immediately before and to complete the search in a short time. To do.

(Means for Solving Problems) A database search system according to the present invention is a nonvolatile auxiliary storage device capable of storing a large amount of data, and a small-capacity volatile main storage device capable of high-speed data access. All of the data that is composed of storage device and integrated with the minimum required redundancy is placed on the auxiliary storage device, and there are a plurality of lowest level index keys that have the index key value and the address of the data on the main storage device. A possessed lowest level index block, an index key value representing the lowest level block, and an upper level block possessing a plurality of upper level index key values possessing an address on the main memory of the lowest level block, Multiple upper-level index keys holding the upper-level block representative index key value and the address of the upper-level block on the main memory An index consisting of a hierarchical structure with the only top-level block possessed by it is placed in the auxiliary storage device, and the top-level block is stored in the main memory in response to a request to retrieve the index using the index key value. By reading on the device and comparing the search key value with the index key value of the upper index key in the top level block, the next higher level index block that seems to contain the same index key value as the search key value is found. Decide,
By performing this to the lowest level block, the lowest level index key included in the lowest level block that matches the search key value is determined, thereby searching the database having the index search means for searching the target data. The system comprises index information saving means, specific block input control means, and lowest level search means.

The index information saving means is for storing and saving the lowest level block number including the latest searched search key and the address of the block in the main storage device.

The specific block input control means indicates the address of the saved block in the storage device when searching the index, and enables the reference when the block exists in the specified storage device. It is for.

The lowest level search means is for determining whether or not the desired index key exists inside the block which can be referred to by the specific block input control means.

(Example) Next, this invention is demonstrated with reference to drawings.

FIG. 1 is a block diagram showing an embodiment for realizing the database search system according to the present invention. In FIG. 1, 10 is an index retrieval means, 11 is an index information record referencing means, 12 is an upper level index retrieval means, 13 is a lowest level index retrieval means, 14 is index information saving means, and 15 is a specific block input control means. , 16 is a main storage device, 17 is an upper level index block, 18 is a lowest level index block, 19 is index save information, and 20 is an auxiliary storage device.

The index search method according to the present invention comprises an index information record reference means 11, an upper level index search means 12, a lower level index search means 13, and an index information saving means 14, an index search means 10, and a specific block input control means 15. , A main storage device 16 and an auxiliary storage device. The index information record reference means 11 and the higher level index search means 12 are the same as the conventional technology.

FIG. 2 is a flow chart showing the processing in the embodiment of FIG. It will be explained based on this.

First, the index search means 10 determines whether the index save information 19 saved in the main memory 16 is valid. The index save information 19 exists one-to-one with the index, and as shown in FIG. 3, a graph showing whether the saved save information is valid or invalid, the block number of the lowest-level index block searched most recently, and the main And the address on the storage device 16. If the index evacuation information 19 is invalid as a result of the determination, a search according to the conventional technique is performed. On the other hand, if the index save information 19 is valid, control is passed to the lowest level index search means 13.

Second, the lowest level index search means 13 is the index save information.
The lowest level block number 19 and the address on the main memory 16 are designated, and an input is requested to the specific block input control means 15.

Third, the lowest level index block number of the input request exists at the designated address on the main memory 16,
If the reference is possible, the specific block input control means 15 makes the reference possible and notifies the lowest level index search means 13.

It is checked whether the block read in the main memory is used for reading another block for the purpose of effective use of the main memory by checking whether the address exists in the main memory 16 or not. Because there is a possibility that

Fourthly, if the non-reference is notified by the specific block input control means 15, the lowest level index retrieval means 13
Notifies the index search means 10 of the above-mentioned state in the same manner as the control of the prior art.

Fifthly, when the specific block input control means 15 notifies that the lowest level block can be referred to immediately before, the lowest level index search means 13 determines the lowest level index key to be obtained. Search for. However, if the lowest level index key obtained at this time is outside the range of the lowest level index block, the lowest level index search means
13 notifies the index search means 10 to perform the search according to the conventional technique.

Sixthly, regardless of the conventional method or the method of the present invention, if the target lowest level index key can be found by the search, the index information saving means 14 stores the index save information 19 in the main memory. Retract on device 16. If the lowest level index key is not found, the flag of the index save information 19 is invalidated.

Also, when the index is searched for the first time, the index save information 19 is saved as invalid.

The index can search the target index key at high speed. However, in order to obtain the final purpose lowest level index key, each search requires a search of the higher level index blocks that make up the index. In the present invention, the information about the lowest level index block including the lowest level block searched immediately before is stored, and the next search is performed from the stored lowest level block, so that the lowest level of the index key used for the next search is stored. When the level block is included in the same block as the index key value searched immediately before, the search of the higher level index block can be omitted, and the time required for the search can be shortened when accessing the index order. You can

(Effect of the invention) As described above, the present invention stores the lowest level index block including the lowest level index key retrieved immediately before, so that the lowest level index key included in the next block is stored. There is an effect that the index search processing can be performed at high speed without repeating the same processing when searching. In particular, the present invention is extremely effective when the index key values are concentrated by the sequential access processing via the index key or the dynamic access via the index.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment for realizing the database search system according to the present invention. FIG. 2 is a flow chart showing the processing in the embodiment of FIG. FIG. 3 is an explanatory diagram showing the format of the index save information. FIG. 4 is a block diagram showing an index search method according to the prior art. FIG. 5 is an explanatory diagram showing the storage status in the index. FIG. 6 is an explanatory diagram showing the format of the index key. 10, 41 …… Index search means 11, 42 …… Index information record reference means 12, 43 …… Upper level index search means 13, 44 …… Lowest level index search means 14 …… Index information saving means 15 …… Specification Block input control means 16,45 ...... Main memory 17,46 …… High level index block 18,47,53 …… Lowest level index block 19 …… Index save information 20,48 …… Auxiliary memory 51 …… Index key information record 52 …… Highest level index block 54 …… High level index key 55 …… Lowest level index key 56 …… Lowest level index key

Claims (1)

(57) [Claims] 1. A non-volatile auxiliary storage device capable of storing a large amount of data and a small-capacity volatile main storage device capable of high-speed data access, and with minimum necessary redundancy. The lowest level index block that has all the integrated data on the auxiliary storage device, and the lowest level index block that holds the index key value and the lowest level index key that holds the address of the data on the main memory, and the lowest level index An index key value representing a block and an upper level index block having a plurality of upper level index key values holding the address on the main storage of the lowest level index block, and an index key value representing the upper level index block And the only top-level index block that has multiple higher-level index keys that have the address on the main memory of the higher-level index block. An index consisting of a hierarchical structure with a key is placed in the auxiliary storage device, and in response to a request to retrieve the index with the index key value, the highest level index block is read into the main storage device and the search key is retrieved. By comparing the value with the index key value of the higher index key in the highest level index block, we determine the next higher level index block that is likely to contain an index key value equal to the search key value, and A database search system having an index search means for searching target data by determining the lowest level index key included in the lowest level index block that matches the search key value by performing the process up to the lower level index block. , The lowest level block number including the search key that was searched most recently, and the address of the block in the main memory. And an index information saving means for storing and saving, and an address of the saved block on the storage device when searching the index, and when the block exists in the specified storage device. Is a specific block input control means for enabling reference, and the lowest level search for determining whether or not the index key to be sought exists inside the block that can be referenced by the specific block input control means. A database search system characterized by comprising means.