JPH1049410A - Different type data base accessing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a different type data base accessing device with which an application program(AP) can access a plurality of different type data bases through a common access interface despite of the type of data bases or data without necessity for the AP to care of which local data base is to be accessed. SOLUTION: This data base accessing device is provided with a data structure defining means 102 for defining a logical data structure unit while relating it with an inquiry instruction to the local data base and a data structure storage area 103 for storing that definition information, the inquiry instruction from the AP is received, the plurality of different type data bases are accessed, and the retrieved result is returned to the AP.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heterogeneous database access apparatus for searching a plurality of different types of databases via a network.

[0002]

2. Description of the Related Art Conventionally, an application program has
When accessing multiple databases, it was necessary to consider the interface specific to the target database. Even for relational databases, SQL is standardized as an access language, but at present the detailed specifications differ for each vendor that provides the database. Furthermore, there are various methods of accessing a database that stores not only numerical data and character data but also multimedia data such as images, sounds, and figures.

On the other hand, Japanese Patent Application Laid-Open No. Hei 5-334363 proposes a database search device provided with a database interface for converting a standard-format SQL passed from an application program into a database-specific format SQL. I have. However, in this method, when one application program accesses a plurality of local databases, the application program needs to operate the database switching unit in order to select a database to be searched.

That is, a plurality of different databases can be accessed by a common access interface, but it is necessary for an application program to be aware of which local database should be accessed.

[0005] Further, when a plurality of databases are accessed via a network, there is a problem that it takes time to communicate data between the databases and the application programs. In particular, it becomes a serious problem when accessing a database at a remote place or when accessing large-capacity data such as multimedia data.

[0006] On the other hand, in Japanese Patent Application Laid-Open No. Hei 6-274401, a data cache mechanism is provided on the application program side to store a query statement and acquired data, and the cached data is stored for the second and subsequent queries. There is a proposal for a method that uses a.

However, in the method disclosed in Japanese Patent Application Laid-Open No. 6-274401, when the cache capacity is exceeded, the cache data with the oldest access date and time is deleted and the latest cache is registered. ,
There is a problem that even if the data in the original database is updated, it remains in an old state.

[0008]

A first object of the present invention is to make an application program aware of a local database to be accessed by a common access interface irrespective of the type of database and the type of data. Another object of the present invention is to provide a database access device that allows an application program to access a plurality of different types of databases.

A second object of the present invention is to reduce the amount of data communication as much as possible when accessing a plurality of databases via a network, and to use the latest data of a local database as much as possible. It is to provide a database access device which can be used.

[0010]

In order to solve this problem, a database access apparatus according to the present invention comprises a query processing unit, a data structure definition unit, a data structure storage area,
It is characterized by comprising a data cache unit, a data cache area, a data cache area search unit, and a plurality of local database access units.

Alternatively, the present invention is a database access apparatus to which any one of a local database inquiry command generation unit, a data conversion unit, and a data cache area adjustment unit is added.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The first and second aspects of the present invention have the following effects. The inquiry from the application program to the heterogeneous database access device may be made for each data structure defined in the data structure storage area. Since the identification of the local database to be accessed and the matters unique to each local database (expression method of query statement, data type, etc.) are included in the definition information of the data structure unit and the access means of the local database, the present database access device is used. When accessing via an application, the application program does not need to be aware of which local database is accessed and how.

Further, since the data once accessed is stored in the data cache area, the search from the second time is performed on the data cache area on the apparatus, so that the data between the local database and the apparatus is Communication volume can be reduced.

The third aspect of the present invention has the following operation. When a plurality of applications use different types of database access devices, it is not necessary for each application to have a conversion means. Also, caching the converted data reduces the load of data conversion. Further, by storing the result of the data compression conversion in the cache area, the communication amount between the heterogeneous database access device and the application can be reduced.

The invention described in claim 4 of the present invention has the following operation. Even if the data in the local database is updated so that it no longer matches the data stored in the cache area, it will be updated as long as the use of the present apparatus is continued. If the data cache area is made smaller, it is less likely that the data structure unit to be queried exists in the cache area, but the contents of the local database are reflected relatively quickly.

On the other hand, if the data cache area is made large, the possibility of mismatch between the original data of the local database and the data of the cache area increases, but the possibility that the data structure unit to be queried exists in the cache area is high. It can be expected to reduce the amount of data communication. As described above, according to the configuration of claim 4, by changing the size of the data cache area, it is possible to use it according to the purpose.

The fifth aspect of the present invention has the following operation. How often the data in the local database is updated often depends on the individual local database. In the configuration of claim 5, by individually adjusting the size of the data cache area of each local database, the latest state of the local database is reflected in the cache area as soon as possible, and the amount of data communication is reduced. The purpose of the data cache can also be achieved.

(Embodiment 1) FIG. 1 is a configuration diagram of a heterogeneous database access device. 101 is an inquiry processing means, 102 is a data structure definition means, 103 is a data structure storage area, 104 is a data cache means, 105 is a data cache area, 106 is a data cache area search means, 107a, b, and c are a plurality of local databases. Access means.

Next, the role of each means and an example of data stored in each area will be described. The data structure defining means defines a logical data structure unit on the heterogeneous database access device. Here, the logical data structure unit is
It is associated with a set of data obtained by querying the local database.

The definition here is made by the administrator of the heterogeneous database access device having information on each local database. FIG. 3 shows two examples of logical data structure unit definition information. Here, it is assumed that the logical data structure unit is one table, and a table name, a column name, and a data type of each column are defined. In addition, the name of the local database to be accessed
Is included in the definition information.

The query sentence of FIG. 3 is an example in which the format of the query sentence differs depending on whether the database to be accessed is DB1 or DB2. The data structure storage area stores definition information on a plurality of data structure units.

The local database access means connects to the local database and issues a query to the local database to the local database. Then, the search result returned from the local database is passed to the data cache unit. At this time, if necessary, the data type is converted from a data type unique to the local database to a common data type defined by the heterogeneous database access device. In the example of Figure 2 and Figure 3, int type → integer type, char
Convert from type to string type.

This means is one of the ordinary application programs of the local database as viewed from the local database. The data type of the image column in FIG. 2 is a variable-length binary data type blob (binary large ob
ject), which is an example of storing image data in the same column.

The data cache means stores the result obtained by making an inquiry to the local database in the data cache area. Then, the head address where the cache data is stored is added to the definition information of the corresponding data structure unit as a cache destination address, and is stored in the data structure storage area in the form shown in FIG.

FIG. 4 shows an example of storing cache data. This is an example in which one data structure unit (here, a table) is further divided into a plurality of records and stored in a list structure.

The query processing means includes a query sent to a heterogeneous database access device (in a standard S format).
It is predetermined in QL or the like. ) To clarify the data structure unit (table name in FIG. 3) to be searched and the search condition. Then, referring to the data structure storage area,
It is determined whether the cache data of the data structure unit to be searched exists in the data cache area. This can be known from the fact that the address of the cache destination is stored in the data structure storage area.

If cache data exists, the cache data storage address and search condition are passed to the data cache area search means. If the cache data does not exist, an inquiry sentence to the local database stored in the data structure storage area is passed to the corresponding local database access means.

The data cache area search means searches the data cache area based on the cache data storage address and the search condition passed from the inquiry processing means, and returns data meeting the search condition to the calling side.

FIG. 5 shows two examples of a query sentence to a heterogeneous database access device. This is an example of an inquiry for a data structure unit (here, a table) defined as shown in FIG. The user or application program that issues these inquiries need only be aware of the data structure units (tables, etc.) on the heterogeneous database access device, and do not need to be aware of which local database stores the original data. .

FIG. 6 is a flowchart showing the processing when the first example of the query sentence of FIG. 5 is issued to the heterogeneous database access device of FIG. Hereinafter, the steps will be described.

First, the application program issues a query (601). Next, the inquiry processing unit clarifies the data structure unit to be searched and the search condition (602). Next, it is determined whether or not there is cache data of the corresponding data structure unit (603). If not, the query processing means passes a query sentence to the local DB to the local DB access means. (The inquiry sentence stored in the data structure storage area is passed as it is.) (604).

Next, the local DB access means issues a query to the local DB. Then, the received search result is passed to the data cache unit (605).
Next, the data cache unit stores the search result in the cache area, and sets a storage destination address in the data structure storage area (606).

Next, the query processing means passes the cache data storage address and the search condition to the data cache area search means (607). Next, the data cache area search means searches the data cache area and returns data matching the search condition to the calling side.

As described above, by using this apparatus, the administrator of this apparatus defines a logical data structure unit,
The application program developer can develop the application program with a common access interface regardless of the type of the local database and without being aware of the local database to be accessed. Further, once accessed data is stored in the data cache area,
Since the search from the second time is performed on the data cache area on the device, the data traffic between the local database and the device can be reduced.

(Embodiment 2) FIG. 7 is a configuration diagram of a heterogeneous database access device. The configuration shown in FIG. 1 is obtained by adding a query instruction generation unit for each local database.

The local database query command generating means includes: (1) a search condition given by a query sent to a heterogeneous database access device; (2) a query sent to a local database stored in a data structure storage area; 3) Based on the three conditions of the current cache data,
Generate a query to the local database with new search conditions to exclude the currently cached data, and pass it to the local database access means.

FIG. 8 is an example of a query sentence to a heterogeneous database access device. FIG. 9 is an example of a query sentence generated by the query instruction generating means of the local database for the query sentence of FIG. The value of id which is the primary key (the column that uniquely identifies the record)
This is an example in the case where data 3 and 4 already exist in the data cache area.

A condition for e_id is added to the search condition (age <30) given in the query sentence of FIG.

FIG. 10 is a flowchart showing the processing when the query sentence of FIG. 8 is issued to the heterogeneous database access device of FIG. Hereinafter, the steps will be described.

First, the application program issues a query (1001). Next, the query processing unit clarifies the data structure unit to be accessed and the search condition, and sends the search condition to the corresponding local DB query command generation unit (1002). Next, it is determined whether or not there is cache data of the corresponding data structure unit (10
03).

If not, the local DB query generating means generates a local DB query based on the search condition and the query stored in the data structure storage area, and executes the local DB access access. Hand over to the means (1004). Next, the local DB access unit issues a query to the local DB. And
Pass the received search result to the data cache unit (1
005).

Next, the data caching means stores the search result in the cache area and sets a storage destination address in the data structure storage area (1006). Next, the inquiry processing means passes the cache data storage address and the search condition to the data cache area search means (1007). next,
The data cache area search means searches the data cache area and returns data meeting the search condition to the calling side (1008).

On the other hand, if there is cache data in step 1003, the inquiry processing means passes the cache data storage address and the search condition to the data cache area search means (1009). Next, the data cache area search means searches the data cache area, specifies the data (record) already cached, and sends it to the corresponding local DB inquiry command generation means (101).
0).

Next, the query sentence generating means of the local DB obtains a new search condition by omitting the data already existing in the data cache area, and based on the query sentence stored in the data structure storage area. , Generates a query sentence to the local DB and passes it to the local DB access access means (1011). Next, the local DB access unit issues a query to the local DB. Then, the received search result is passed to the data cache unit (1012).

Next, the data caching means additionally stores the search result in the cache area (1013). next,
Data cache area search means searches the data cache area and returns data that meets the search conditions to the calling side.

As described above, by using this apparatus, the administrator of this apparatus defines a logical data structure unit,
The application program developer can develop the application program with a common access interface regardless of the type of the local database and without being aware of the local database to be accessed. Further, once accessed data is stored in the data cache area,
Since the search from the second time is performed on the data cache area on the device, the data traffic between the local database and the device can be reduced.

Here, the differences between the first and second embodiments are as follows. In the first embodiment, when an inquiry is made to a data structure unit (such as a table), all data in the corresponding data structure unit is acquired and stored in the data cache area.

Therefore, while the amount of data stored in the data cache area is small, the amount of data communication between the local database and the access device increases. However, in the second embodiment, only a portion (record) that matches the search condition is acquired and cached, so that such a case does not occur.

(Embodiment 3) FIG. 11 is a configuration diagram of a heterogeneous database access device. The data conversion means is added to the configuration of FIG.

The query processing means, in addition to the processing described in the first embodiment, interprets the query sentence and clarifies the data conversion target and the conversion method.

The data conversion means has a plurality of processing means corresponding to the plurality of data conversion methods, and performs data conversion processing on the data passed from the data cache means according to the data conversion method designated by the inquiry processing means. And returns the result to the data cache.

FIG. 12 is an example of a query sentence to a heterogeneous database access device. It specifies that the image column data is returned after being converted by half_size ().

FIG. 13 shows an example of storage in the cache area. Only one record is shown. Embodiment 1
Compared to the case. In the first embodiment, only data is stored in the cache area. In the present embodiment, however, a combination of a conversion method name and data converted by the conversion method is stored.

FIG. 14 shows the query sentence of FIG.
9 is a flowchart illustrating a process when the command is issued to one heterogeneous database access device. The steps are described below.

First, the application program issues a query (1401). Next, the query processing means includes a data structure unit to be accessed, a search condition,
Further, the data conversion method is clarified (1402). Next, it is determined whether there is cache data of the corresponding data structure unit (1403). If not, the query processing means passes the query sent to the local DB to the local DB access means. (The query sentence stored in the data structure storage area is passed as it is.) (140
4).

Next, the local DB access means issues a query to the local DB. Then, the received search result is passed to the data cache unit (140
5). Next, the data cache unit stores the search result in the cache area, and sets a storage destination address in the data structure storage area (1406). The inquiry processing means passes the cache data storage address, the search condition, and the data conversion method to the data cache area search means, and passes the data conversion method to the data conversion means (1407). Next, the data conversion means performs data conversion processing on the data in the data cache area, and stores the result in the data cache area (1408). Next, the data cache area search means searches the data cache area and returns data meeting the search condition to the calling side (1409).

On the other hand, if there is cache data in step 1403, the query processing means passes the cache data storage address, search condition, and data conversion method to the data cache area search means (1410). next,
The data cache area search means searches the data cache area and checks whether cache data of the corresponding data conversion method exists (1411).

Next, it is determined whether or not there is cache data of the corresponding conversion method.
If there is, go to step 1409.

As described above, when a plurality of applications use a heterogeneous database access device, it is not necessary for each application to have a conversion means. Also, by caching the converted data,
The load of data conversion is also reduced. Further, by storing the result of the data compression conversion in the cache area, the communication amount between the heterogeneous database access device and the application can be reduced.

Note that a similar effect can be obtained with a configuration in which data conversion means is added to the configuration of the second embodiment.

(Embodiment 4) FIG. 15 is a configuration diagram of a heterogeneous database access device. This is obtained by adding a data cache area adjusting means to the configuration of FIG.

When the data cache area is full, the data cache area adjusting means erases data stored in the data cache area in order from the oldest stored time in the data structure unit. further,
When the data is deleted from the data cache area, the address data of the cache destination in the data structure storage area is also deleted.

As described above, even if the data in the local database is updated and no longer matches the data stored in the cache area, the data will be updated as long as the apparatus is used. If the data cache area is made smaller, it is less likely that the data structure unit to be queried exists in the cache area, but the contents of the local database are reflected relatively quickly.

On the other hand, if the data cache area is made relatively large, the possibility of mismatch between the original data of the local database and the data of the cache area increases. However, it is possible that the data structure unit to be queried exists in the cache area. It can be expected to reduce the amount of data communication.

A similar effect can be obtained even in a configuration in which the data cache area adjusting means is added to the configuration of the second or third embodiment.

(Embodiment 5) FIG. 16 is a configuration diagram of a heterogeneous database access device. This configuration is an extension of the configuration of FIG. 15 in which a data cache unit, a data cache area, and a data cache area adjustment unit are provided for each local database.

How often the data in the local database is updated often depends on each local database.

For example: The local database 1 has a low update frequency.

The local database 2 has a high update frequency. In such a case, the cache area of the local database 1 is increased.

The cache area of the local database 2 is reduced. According to the configuration of FIG. 17, the latest state of the local database is reflected in the cache area as soon as possible.
In addition, the purpose of the data cache of reducing the amount of data communication can be achieved.

As described above, by individually adjusting the size of the data cache area of each local database, the latest state of the local database is reflected in the cache area as soon as possible, and the amount of data communication is reduced. It is also possible to achieve the purpose of the data cache.

[0072]

As described above, according to the present invention, a common access interface is used regardless of the type of database and the type of data, and the application program is not conscious of which local database is to be accessed. It is possible to provide a database access device that allows a program to access a plurality of different databases.

Further, there is provided a database access apparatus capable of reducing the amount of data communication as much as possible when accessing a plurality of databases via a network and using the latest data of a local database as much as possible. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a heterogeneous database access device according to a first embodiment of the present invention.

FIG. 2 is a data example diagram of a local database.

FIG. 3 is an example diagram of definition information stored in a data structure area.

FIG. 4 is an example of storage in a data cache area;

FIG. 5 is an example diagram of a query sentence to a heterogeneous database access device.

6 is a flowchart showing the flow of processing when the query sentence of Example 1 in FIG. 5 is issued to the heterogeneous database access device in FIG.

FIG. 7 is a configuration diagram of a heterogeneous database access device according to the second embodiment.

FIG. 8 is an example diagram of a query sentence to a heterogeneous database access device.

FIG. 9 is a diagram illustrating an example of a query sentence generated by a query command generation unit of a local database.

FIG. 10 is a flowchart showing a processing flow when the query sentence of FIG. 8 is issued to the heterogeneous database access device of FIG. 7;

FIG. 11 is a configuration diagram of a heterogeneous database access device according to the third embodiment.

FIG. 12 is an example diagram of a query sentence to a heterogeneous database access device.

FIG. 13 is an example of storage in a data cache area.

14 is a flowchart showing the flow of processing when the query sentence of FIG. 12 is issued to the heterogeneous database access device of FIG.

FIG. 15 is a configuration diagram of a heterogeneous database access device according to the fourth embodiment.

FIG. 16 is a configuration diagram of a heterogeneous database access device according to the fifth embodiment.

[Explanation of symbols]

 101 inquiry processing means 102 data structure definition means 103 data structure storage area 104 data cache means 105 data cache area 106 data cache area search means 107a local database access means 107b local database access means 107c local database access means

Claims (5)

[Claims] 1. A database access device that receives an inquiry command from an application program, accesses a plurality of different types of local databases, and returns search results to the application program, inquires a local database, and obtains a result. A plurality of local database access means, a data cache area for storing query results obtained by the local database access means, and a data cache means for storing the query results obtained by the local database access means in the data cache area A data structure defining means for defining a logical data structure unit in association with a query instruction to a local database; and a data storing definition information by the data structure defining means. Query processing means for interpreting a query from an application program and determining whether cache data corresponding to a data structure unit to be searched is stored in the data cache area, and searching the data cache area, A data cache area retrieving means for returning to the application program data matching the retrieval condition interpreted by the query processing means. 2. A heterogeneous database access device according to claim 1, further comprising: an inquiry command from an application program; an inquiry command to a local database stored in a data structure storage area; and data stored in a data cache area. A heterogeneous database access apparatus, comprising: a plurality of local database inquiry command generating means for generating a new local database query command based on the local database access means. 3. The heterogeneous database access device according to claim 1, comprising a plurality of processing units corresponding to the plurality of data conversion methods, and a data conversion unit for performing data conversion according to the specified data conversion method. Characteristic heterogeneous database access device. 4. The heterogeneous database access device according to claim 1, wherein, when the data cache area runs out of room, of the data structure units stored in the data cache area, the stored time is set from the oldest stored time. A heterogeneous database access device comprising a data cache area adjusting means for sequentially deleting data. 5. A heterogeneous database access device according to claim 4, wherein a plurality of data cache means, data cache areas, and data cache area adjustment means are provided in correspondence with each local database access means. Access device.