JPH03189741A - Remote data base access method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a remote database access method using the database language SQL, and particularly relates to a remote database access method suitable for use when accessing by cursor operation. .

(Prior Art) Generally, when performing remote database access (for example, remote access to a relational database) using the database language SQL, cursor operations are performed using the following methods: cursor declaration (declaration statement), cursor open (execution statement), etc. is sent to the server side, and after the processing is executed, a row data retrieval request (FETCH statement) is sent to the server side, and one row data is returned, and this FETCH
By repeatedly transferring statements and returning the resulting row data,
All row data that met the conditions specified in the cursor declaration was being retrieved.

(Problems to be Solved by the Invention) As described above, in remote database access in conventional SQL cursor operations, by repeating the transfer of the FETCH statement and the return of the resulting row data, the conditions specified in the cursor declaration are Because all the row data that satisfies the requirements were retrieved, it took a lot of time to transfer the FETCH statement and the resulting row data.Also, it was necessary to repeatedly transfer the same FETCH statement and to transfer the resulting row data one by one. There is a problem in that the amount of data to be transferred increases due to the transfer.

The present invention has been made in view of the above circumstances, and when remote database access is performed using the database language SQL, the server side sends all row data that satisfies the conditions specified in the cursor declaration to the client at the time of the cursor declaration or when the cursor is opened. Transfer to the side and subsequent FETC
Execute the H statement only on the client side,
It is an object of the present invention to provide a remote database access method that can significantly reduce the time and amount of transfer of FETCH statements, line data, etc. between the client side and the server side.

[Structure of the Invention] (Means and Effects for Solving the Problems) The remote database access method according to the present invention provides the client side with all row data that satisfies the conditions of the cursor declaration, as shown in FIG. 2(a). Provide a means for retrieving, transferring to the client side when declaring a cursor or opening a cursor,
This is achieved by providing a means on the server side to store the row data group received from the server side and to extract and execute subsequent FETCH statements one by one from the stored row data group, as shown in FIG. Ru. That is, when the client receives a cursor declaration or a cursor open request from a user accessing a remote database, the client transmits the access request to the server. When the server receives the access request, it accesses the target database and passes all row data that satisfies the conditions of the cursor declaration to the client. The client stores all row data that satisfies the conditions of the cursor declaration received from the server in the main memory or auxiliary storage, and thereafter, when it receives a FETCH statement from the user, retrieves one item from the row data stored in the storage device. ,
Return it to the user. Such remote database access allows FET between the client side and the server side.
The time and amount of transfer of CH statements, line data, etc. can be significantly reduced.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration according to an embodiment of the present invention.

In FIG. 1, ``■'' is a client consisting of one computer organization, and a user's application program that accesses a remote database runs thereon. A server 2 is a computer organization different from the client 1, and there is a database to be accessed remotely.

A communication line 3 serves as a communication path between the client 1 and the server 2, and enables information exchange between the computer of the client 1 and the computer of the server 2. Reference numeral 11 denotes a user program provided in the client 1, which issues requests for remote database access such as cursor declaration, cursor opening, and FETCH statements. 12 is a processing program A provided in the client l, and is shown in FIG.
) Executes remote database access processing including the processing functions shown in ().

Reference numeral 21 denotes a database provided in the server 2, which is a target of remote database access. 22 is a processing program B provided in the server 2, which executes remote database access processing including the processing functions shown in FIG. 2(b).

FIG. 2 is a flowchart showing the operation processing procedure in an embodiment of the present invention, in which (a) is a flowchart showing the processing procedure of the client 1, and (b) is a flowchart showing the processing procedure of the server 2.
2 is a flowchart showing a processing procedure.

In FIG. 2, 81 to S4 are processing steps of client I, and among these, Sl determines whether the request from the user accessing the remote database is a cursor declaration, a cursor open, or a FETCH statement. Step S2 is a step of extracting one item from the row data stored in step S4 and returning it to the user when the user's request is a FETCH statement. When the request from the user is to declare a cursor or open a cursor, S3
This is a step of sending a remote database access request to the server 2, and notifies the server 2 of a cursor declaration or cursor open request. S4 is a step in which all row data satisfying the conditions specified in the cursor declaration is received from the server 2 and stored, and all row data returned from the server 2 is stored in the main storage or auxiliary storage in the computer organization of the client 1. Store in device. Sll and S12 are processing steps of the server 2, and among these, Sll is a step for receiving a request from the client l. S12 is a step of returning the line data to the client 1, in which the database 21 is accessed in accordance with a request from the client 1, all line data satisfying the conditions specified in the cursor declaration are retrieved, and the data is returned to the client 1.

The operation of an embodiment of the present invention will now be described with reference to FIGS. 1 and 2.

When the client 1 receives a cursor declaration or a cursor open request from a user who is accessing a remote database, it notifies the server 2 of the access request via the communication line 3 (steps S1 and S3 in FIG. 2). That is, when a cursor declaration or a cursor open request is issued from the user program 11, the processing program A12 of the client 1 transmits the access request to the processing program B2 of the server 2 via the communication line 3 using a predetermined communication means.
Hand it over to 2.

When the server 2 receives the above access request from the client l, it accesses the target database 21, retrieves all the row data that satisfies the conditions of the cursor declaration, and sends the row data back to the client l (step Sll in FIG. 2). , 512). That is, when the processing program B 22 of the server 2 receives the above access request from the processing program A 12 of the client 1 via the communication line 3, it accesses the target database 21 and retrieves all row data that satisfies the conditions of the cursor declaration. , transfers all of the row data to the processing program A12 of the client l via the communication line 3.

The client 1 stores all line data according to the cursor command received from the server 2 in the main memory or auxiliary memory (step S4 in FIG. 2). That is, the processing program AI2 of the client 1 is sent to the server 2 via the communication line 3.
When the line data according to the cursor declaration is received from the processing program B22, all of the line data is stored in the main memory or auxiliary memory of the computer that is subject to its own access control.

After that, when the client l receives a FETCH statement from the user, it retrieves one item from the row data stored in the main storage device or auxiliary storage device and returns it to the user (step S2 in FIG. 2). That is, from the user program 11
When the CH statement is issued, the processing program A12 does not update the data with the server 2, but accesses the main storage device or auxiliary storage device under its own control and reads one item from the row data stored in the storage device. is taken out and returned to the user program 11. In this way, when the client l receives a FETCH statement from the user, it does not send the FETCH statement to the server 2, but retrieves one item from the row data stored in the main storage or auxiliary storage that is under its control. and hand it to the user. This process is repeatedly executed every time a FETCH statement is received. Therefore, there is no need to transfer FETCH statements or row data between client 1 and server 2 via a communication path, and the processing load on client 1 and server 2 is significantly reduced, resulting in high-speed and A smooth remote database access mechanism can be realized.

The remote database access method described above is widely applicable to various remote database access mechanisms and distributed database mechanisms.

[Effects of the Invention] As detailed above, according to the remote database access method of the present invention, when remote database access is performed using SQL, all row data that satisfies the conditions specified in the cursor declaration can be accessed using the cursor. Transferred to the client side when declaring or opening a cursor, and subsequent FETC
By executing the H statement only on the client side,
The time and amount of transfer of FETCH statements, line data, etc. between the client side and the server side can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 (
Figures a) and (b) respectively show the processing flow of the above embodiment, where (a) is a flowchart showing the processing procedure on the client side, and (b) is a flowchart showing the processing procedure on the server side. .

Claims (1)

[Claims] When accessing a remote database using SQL, all row data that satisfies the conditions specified in the cursor declaration is transferred to the client side when the cursor is declared or opened, and subsequent FETCH statements are executed only on the client side. A remote database access method characterized by: