JPH11154109A - System for dividing index storage area - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the efficiency of a page use which does not become the storage destination of continuous key values and to improve the page use rate as a whole by adjusting a storage destination page with the key value which is logically positioned in the center as a reference in a key value group in the page. SOLUTION: If an entry having a key value '28' is added when the entries which continuously have '27' from the key value '22' are added, they are added in the latter half with the entry having the key value '23' which is logically Positioned in the center of an index page P2 as the reference. Thus, a boundary is decided between the entry group to the entries having the key value '27' which is smaller than the key value '28' of the added entry and which is the nearest and the remaining entry group containing the entries having the added key value '28'. The entry group which does not contain the entry having the added key value '28' based on the decided boundary is moved to an index page P3 and a division processing is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a database management system having an index, and more particularly, to a method of dividing an index storage page when adding a key value to a page having no empty area.

[0002]

2. Description of the Related Art Conventionally, in a database management system, when an attempt is made to add a key value to a page having no empty area, the number of keys in the page is equally divided as described in JP-A-62-211748. An equal-division method that divides and stores the data into one page, and a key-value-sequential storage time-division method that divides and stores the logical value at a logical addition position of the page as a boundary are used.

[0003]

In the conventional equal-division storage method described above, when data is successively added in the order of the key value, the empty area occupies about 50% of the page every time the page is divided, and the page utilization rate is increased. There is a problem that is worse. Also,
In the key value order storage time division method, when data is successively added in the key order, the page to be added is a page in which the smaller key value adjacent to the value is stored. Immediately after the value, in the database management system where the page to be added is a page in which a large key value adjacent to the value is stored, the page is divided and stored just before the additional key value as a boundary in the order of the key value.
Depending on the addition position, there is a problem that the utilization rate of a page to which data is not continuously added in the order of the key value after page division may be less than 50%.

SUMMARY OF THE INVENTION An object of the present invention is to, when data is successively added in the order of a key value, set a key value group in a page having no empty area to which the key value is to be added in a logical addition position of the key value to the page. When storing in two pages with a boundary as a boundary, it is predicted that a continuous key value will be added later, a large empty area of the page as a storage destination of the continuous key value is secured, and a continuous key value is stored. It is an object of the present invention to provide a page division method capable of adjusting so as to increase the usage rate of a page that does not store a value and improving the overall page usage rate.

[0005]

In order to solve the above-mentioned object, a page dividing method according to the present invention predicts that a continuous key value will be added later, and sets a page as a storage destination of the continuous key value. If the logical addition position of the key value to the target page is the first half based on the key value that is logically located at the center of the key value group in the page to secure a wide empty area of The page is characterized in that the page in which the smaller key value group is stored in the division and the page in which the larger key value group is stored in the second half are set as the storage destination page of the additional key value.

[0006]

Embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 shows an online system configuration including a database management system according to an embodiment of the present invention. In FIG. 1, an online terminal 11 used for online processing and an external storage device 13 for storing a database 12 are connected to the computer 10. The electronic computer has an online program 14 for performing transaction control based on input from a terminal, a business program 15 for performing transaction processing, and storing data in an external storage device 13 storing a database 12 in response to a request from the business program. , A database management system 16 for performing the retrieval.

FIG. 2 shows an example of the configuration of the database 12. The data page 22 stores data 21.
And an index unit 2 for managing data storage positions
Consists of three. The index 23 has a tree structure, and has an entry 24 including a key value and pointer information indicating a storage position of data having the key value. When a data storage request is received from the business program, an index page as a storage destination of an entry having pointer information indicating a storage position of additional data is determined, and it is checked whether there is an empty area to which an entry can be added. As a result, when there is no empty area to which an entry can be added, the index page is divided.

FIGS. 3A, 3B and 4
(A) and (B) show the transition of the storage state of the index entry according to the present invention, and when determining the page to which the entry is to be added, the entry having the largest and closest key value is stored. An example in which a unit for storing a page is used will be described with reference to a flowchart showing the flow of the index page division process in FIG.

First, in step 41, whether the entry is to be added in the first half of the index page (the key value of the entry to be added is equal to or less than the key value of the entry in the index page that is logically located in the middle) It is checked whether the latter half (the key value of the entry to be added is larger than the key value of the entry located logically in the middle of the entries in the index page).

Next, it is predicted that an entry having a continuous key value will be added later, and the division is performed so as to secure a wide empty area of an index page as a storage destination of the entry having a continuous key value. The boundaries are determined as follows.

When an entry having a key value "21" is added to an index page P1 having no empty area as shown in FIG. 3A, a key value "50" logically located at the center of the index page P1 is added. Is added to the first half based on the entry having ".", YES is selected, and in step 42, from the entry having the minimum key value "10" in the index page P1 including the entry to be added, A boundary is determined between the entry group up to the entry having the closest key value “40” that is larger than the key value “21” and the remaining entry group.

Next, in step 44, the entry group including the entry having the key value "21" to be added based on the determined boundary is moved to the index page P2, and the division processing is completed.

Further, "2" continues from the key value "22".
When the entry having the key value "28" is added in a state as shown in FIG. 4A in which the entry up to the entry having "7" is added, the entry is logically located at the center of the index page P2. Since the entry having the key value "23" is added to the latter half based on the entry, "NO" is selected, and in step 43, the entry having the key value "27" smaller than and closest to the key value "28" of the entry to be added is selected. A boundary is determined between the entry group up to the entry and the remaining entry group including the entry having the key value “28” to be added.

Next, in step 44, the entry group not including the entry having the key value "28" to be added based on the determined boundary is moved to the index page P3, and the division processing is completed.

As described above, according to the page division processing method according to the present embodiment, the page utilization rate can be improved by dynamically determining the storage location of the divided additional entry.

[0017]

As described above, according to the page dividing method of the present invention, when data is continuously added in the key order, the page utilization rate of the entire storage device can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of an online system having a database according to the present invention.

FIG. 2 is a diagram showing a configuration example of a database to which the present invention is applied.

FIGS. 3A and 3B are diagrams showing transition of a use state of a page when an entry is added to the first half of the page according to the present invention.

FIGS. 4A and 4B are diagrams showing transition of a use state of a page when an entry is added to the latter half of the page according to the present invention.

FIG. 5 is a flowchart illustrating a flow of a page division process.

[Explanation of symbols]

11: Online terminal, 12: Database, 1
3 external storage device 14 online management program 15 business program 16 database management program 21 data 2
2 ... data page, 23 ... index page, 24
… Index entry,

Claims (1)

[Claims] In a database management system that divides a storage area into pages and stores index key values in key order in each page, when a key value is added to an index storage page having no empty area, When a key value group is divided and stored in two pages with the logical addition position of the key value to the page as a boundary, it is predicted that successive key values will be added later, and the storage destination of the successive key values In order to secure a large empty area on the target page, the logical addition position of the key value to the target page is set in the first half of the key value group in the page, based on the key value that is logically located in the center. If so, adjust the page where the smaller key value group is stored in the division, and if it is the second half, adjust the page where the larger key value group is stored as the storage page for the additional key value , Page division method characterized by improving the page utilization.