WO2018225315A1 - Database management device, database management system, and database management method - Google Patents

Abstract

A database management device of an embodiment includes a transmission and reception management unit, a query execution unit, and a buffer management unit. The transmission and reception management unit receives a query from an application terminal and reads, from a buffer memory, a query result that is search target data of the query to transmit the read query result to the application terminal. The query execution unit acquires the query result by executing a process based on the query. The buffer management unit determines, on the basis of an evaluation value for communication with the application terminal, whether to store the query result acquired by the query execution unit in the buffer memory, when the communication with the application terminal is cut off.

Description

Database management apparatus, database management system, and database management method

Embodiments described herein relate generally to a database management device, a database management system, and a database management method.

In the field of field IoT (Internet of Things), a database management system in which a database management device and an application terminal are connected is known. In the database management system, the application terminal executes the application and transmits a query for requesting data to the database management apparatus. On the other hand, the database management apparatus executes processing based on the query received from the application terminal to acquire data (query result), and transmits the acquired data to the application terminal.

If the network connection environment of the database management system is unstable, communication between the database management device and the application terminal may be suddenly disconnected. In this case, the database management device temporarily stores the query result that could not be sent to the application terminal in the buffer memory in the kernel network layer, and after the communication between the database management device and the application terminal is restored, The query result was resent to the application terminal.

However, the database management apparatus accumulates the query results in the buffer memory in the order in which the query results are acquired, and if the data amount of the query results stored in the buffer memory exceeds a predetermined amount, the database management apparatus performs a query as a buffer full error. The processing based on was stopped. For this reason, there are cases where the query result cannot be retransmitted depending on the convenience of the application.

JP 2014-146291 A

A problem to be solved by the present invention is a database management apparatus and database management capable of retransmitting query result data according to the convenience of an application even when the network connection environment of the database management system is unstable A system and a database management method are provided.

The database management apparatus according to the embodiment includes a transmission / reception management unit, a query execution unit, and a buffer management unit. The transmission / reception management unit receives a query from an application terminal that executes an application, and reads a query result that is data to be searched for the query from a buffer memory and transmits the query result to the application terminal. The query execution unit acquires the query result by executing a process based on the query received by the transmission / reception management unit. The buffer management unit determines whether or not to store the query result acquired by the query execution unit in the buffer memory when communication with the application terminal is disconnected. Determine based on.

1 is a block diagram showing the overall configuration of a database management system 10 according to a first embodiment. The block diagram for demonstrating operation | movement of the application terminal 100 and database management apparatus 200 which concern on 1st Embodiment. The figure which shows an example of table T1 which concerns on 1st Embodiment. The figure which shows an example of the transmission process of the packet which concerns on 1st Embodiment. The figure which shows an example of the transmission process of the packet which concerns on 1st Embodiment. The figure which shows an example of the transmission process of the packet which concerns on 1st Embodiment. The figure which shows an example of the transmission process of the packet which concerns on 1st Embodiment. The figure which shows an example of the transmission process of the packet which concerns on 1st Embodiment. The flowchart which shows the detail of the state monitoring process which concerns on 1st Embodiment. The flowchart which shows the detail of the normal cutting process which concerns on 1st Embodiment. 6 is a flowchart showing details of query result entry reception processing according to the first embodiment. 6 is a flowchart showing details of packet creation processing according to the first embodiment. 6 is a flowchart showing details of error processing according to the first embodiment. The flowchart which shows the detail of the transmission continuation process which concerns on 1st Embodiment. The flowchart which shows the detail of the query process which concerns on 1st Embodiment. The figure which shows an example of table T2 which concerns on 3rd Embodiment. 14 is a flowchart showing details of query result entry reception processing according to the third embodiment. The flowchart which shows the detail of the query process which concerns on 3rd Embodiment.

Hereinafter, a database management device, a database management system, and a database management method of an embodiment will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing an overall configuration of a database management system 10 according to the first embodiment. The database management system 10 includes a database management apparatus 200 and a plurality of application terminals 100-1, 100-2, and 100-3. In FIG. 1, three application terminals 100-1, 100-2, and 100-3 are shown, but the number of application terminals is not limited to this. For example, four or more application terminals 100 may be connected to the database management apparatus 200.

Application terminals 100-1, 100-2, and 100-3 are terminals that execute an application and transmit a query for requesting data to the database management apparatus 200. The application terminals 100-1, 100-2, and 100-3 are desktop computers, but are not limited thereto. For example, the application terminal 100 may be a notebook computer, a tablet terminal, or a PDA (Personal Digital Assistant).

The database management apparatus 200 receives queries from the application terminals 100-1, 100-2, and 100-3, and sends query results that are data to be searched for the queries to the application terminals 100-1, 100-2, and This is a device that transmits to 100-3. For example, the database management apparatus 200 is a smart meter that accumulates daily power consumption data, but is not limited thereto. The database management apparatus 200 is connected to a plurality of application terminals 100-1, 100-2, and 100-3 via a network NW. The network NW includes, for example, a part or all of a WAN (Wide Area Network), a LAN (Local Area Network), the Internet, a provider device, a wireless base station, a dedicated line, and the like.

FIG. 2 is a block diagram for explaining operations of the application terminal 100 and the database management apparatus 200 according to the first embodiment. Since application terminals 100-1, 100-2, and 100-3 perform the same operation, they will be collectively described as application terminal 100 in FIG.

The application terminal 100 includes an application execution unit 110 and a packet size determination unit 120. The application execution unit 110 and the packet size determination unit 120 are realized by a processor such as a CPU (Central Processing Unit) executing a program stored in a program memory. Note that the application execution unit 110 and the packet size determination unit 120 include an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), and an FPGA (Field-Programmable Gate Array) that have the same functions as a processor executing a program. ) Or the like.

The database management apparatus 200 includes a transmission / reception management unit 210, a connection management unit 230, a query execution unit 240, a buffer management unit 250, a communication quality determination unit 260, a buffer memory 270, and a storage unit 280. The transmission / reception management unit 210, the connection management unit 230, the query execution unit 240, the buffer management unit 250, and the communication quality determination unit 260 are realized by a processor such as a CPU executing a program stored in a program memory. The transmission / reception management unit 210, the connection management unit 230, the query execution unit 240, the buffer management unit 250, and the communication quality determination unit 260 are an LSI, an ASIC, an FPGA, or the like that has the same function as a processor that executes a program. It may be realized by hardware.

The buffer memory 270 and the storage unit 280 are, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), an HDD (Hard Disk Drive), a flash memory, or a hybrid storage device in which a plurality of these are combined. Realized. Further, some or all of the buffer memory 270 and the storage unit 280 may be external devices accessible by the database management apparatus 200, such as NAS (Network Attached Storage) or an external storage server.

The storage unit 280 stores various data. For example, in the case of a smart meter, daily power consumption data is accumulated in the storage unit 280. The data stored in the storage unit 280 is not limited to the power consumption data, and any data may be used. The storage unit 280 stores data in a table format.

The connection management unit 230 manages the connection between the application terminal 100 and the database management apparatus 200. The connection management unit 230 includes a packet size determination unit 231. The packet size determination unit 231 negotiates with the packet size determination unit 120 of the application terminal 100 to determine the maximum packet size that can be used between the database management apparatus 200 and the application terminal 100. For example, the maximum packet size may be obtained using a technique such as Path MTU Discovery or may be determined in advance.

The application execution unit 110 of the application terminal 100 executes the application and transmits a query for requesting data to the database management apparatus 200. The transmission / reception management unit 210 of the database management apparatus 200 outputs the query received from the application terminal 100 to the connection management unit 230. The connection management unit 230 outputs the query input from the transmission / reception management unit 210 to the query execution unit 240.

The query execution unit 240 acquires a query result from the storage unit 280 by executing a process based on the query input from the connection management unit 230. The query execution unit 240 outputs the acquired query result to the buffer management unit 250.

On the other hand, the transmission / reception management unit 210 outputs the header information necessary for transmitting the query result to the application terminal 100 to the buffer management unit 250. For example, the header information is address information of the transmission destination of the query result. The buffer management unit 250 adds the header information input from the transmission / reception management unit 210 to the query result input from the query execution unit 240 to generate a packet.

Specifically, the buffer management unit 250 generates a packet in which header information is added to one or more records of the query result within a range that fits within the maximum packet size determined by the packet size determination unit 231. The buffer management unit 250 stores the generated packet in the buffer memory 270. Further, the buffer management unit 250 outputs a packet transmission request to the transmission / reception management unit 210.

The transmission / reception management unit 210 reads the packet specified by the transmission request from the buffer memory 270 based on the packet transmission request input from the buffer management unit 250. Thereafter, the transmission / reception management unit 210 transmits the packet read from the buffer memory 270 to the application terminal.

Note that, when communication between the application terminal 100 and the database management apparatus 200 is abnormally disconnected, the query result packet is not transmitted to the application terminal 100 but is stored in the buffer memory 270. Therefore, the buffer management unit 250 manages the data stored in the buffer memory 270 using the table T1.

FIG. 3 is a diagram illustrating an example of the table T1 according to the first embodiment. The table T1 is a table in which the connection source ID, communication quality, connection state, accumulation permission ratio, buffer usage amount, and count value are associated with each other.

The connection source ID is identification information of the application terminal 100 connected to the database management apparatus 200. For example, the connection source ID is information including an IP address and a port number. The communication quality is information indicating the quality of the communication line between the database management apparatus 200 and the application terminal 100. The communication quality is any value from “0” to “3”, and the smaller the value, the better the quality of the communication line. For example, “0” indicates that the communication quality is the best and abnormal disconnection hardly occurs. On the other hand, “3” indicates that the communication quality is the worst and abnormal disconnection is likely to occur. Although details will be described later, the communication quality is determined by the communication quality determination unit 260.

The connection state is information indicating whether the communication between the database management apparatus 200 and the application terminal 100 is “connected” or “abnormally disconnected”. The accumulation permission ratio is information indicating the ratio of the amount of data permitted to be accumulated in the buffer memory 270. Even when the accumulation permission ratio is “0%”, it is permitted to accumulate at least one packet of data in the buffer memory 270 in order to transmit a packet.

The buffer usage amount is information indicating the data amount in the buffer memory 270 that is actually used. The count value is a value used for calculating the communication quality, and details will be described later.

The connection source ID is 6 bytes, the communication quality is 2 bits, the connection state is 1 bit, the storage permission ratio is 6 bits (upper limit: 100), and the buffer usage is 6 bits (upper limit: 100) and the count value is 2 bytes. For this reason, one entry in the table T1 is composed of a total of 10 bytes.

When the communication between the database management device 200 and the application terminal 100 is disconnected, the buffer management unit 250 determines whether or not to store the query result packet acquired by the query execution unit 240 in the buffer memory 270, in the table T1. Determine using. Specific processing will be described below.

4 to 8 are diagrams illustrating an example of packet transmission processing according to the first embodiment. 4 to 8 show, as an example, a case where the database management apparatus 200 transmits a packet to three applications A1, A2, and A3.

4 to 8, the communication quality of the application A1 is “1”, and the accumulation permission ratio is “0%”. The communication quality of the application A2 is “0”, and the accumulation permission ratio is “0%”. The communication quality of the application A3 is “2”, and the accumulation permission ratio is “0%”.

First, in FIG. 4, the database management apparatus 200 and the applications A1, A2, and A3 are normally connected. Therefore, the packet stored in the buffer memory 270 by the buffer management unit 250 is immediately transmitted to any of the applications A1, A2, and A3 by the transmission / reception management unit 210, and the transmitted packet is deleted from the buffer memory 270. . As described above, the accumulation permission ratio is “0%”, but the use of the buffer memory 270 is permitted for at least one packet. Therefore, packets are not continuously stored in the buffer memory 270.

FIG. 5 shows a case where communication between the database management apparatus 200 and the application A2 is abnormally disconnected. In this case, the transmission / reception management unit 210 cannot transmit a packet to the application A2.

Therefore, as shown in B1, the buffer management unit 250 changes the accumulation permission ratio for the application A2 in the table T1 from “0%” to “100%”. Thus, packets for the application A2 continue to be accumulated in the buffer memory 270 until communication between the database management apparatus 200 and the application A2 is restored.

FIG. 6 shows a case where communication between the database management apparatus 200 and the application A3 is abnormally disconnected from the state shown in FIG. In this case, the transmission / reception management unit 210 cannot transmit a packet not only to the application A2 but also to the application A3.

Therefore, the buffer management unit 250 updates the accumulation permission ratio in the table T1. Specifically, the buffer management unit 250 calculates the accumulation permission ratio by dividing the communication quality of each application by the total value of the communication quality of the applications for which communication is disconnected.

6, the communication quality of the application A2 is “0”, and the communication quality of the application A3 is “2”. Therefore, the buffer management unit 250 changes the accumulation permission ratio for the application A2 in the table T1 from “100%” to “0%” as shown in B2. Further, as shown in B3, the buffer management unit 250 changes the accumulation permission ratio for the application A3 in the table T1 from “0%” to “100%”.

Since the accumulation permission ratio for the application A2 is changed to “0%”, the buffer management unit 250 does not store the packet for the application A2 in the buffer memory 270. Further, since the accumulation permission ratio for the application A3 is changed to “100%”, the buffer management unit 250 accumulates the packets for the application A3 in the buffer memory 270.

When the buffer memory 270 becomes full, the buffer management unit 250 overwrites the packet for the application A2 stored in the buffer memory 270 with the packet for the application A3.

When neither communication of the applications A2 and A3 is restored, the packet for the application A2 stored in the buffer memory 270 is overwritten with the packet for the application A3. Eventually, all packets for application A2 stored in buffer memory 270 will be overwritten with packets for application A3.

FIG. 7 shows a case where communication between the database management apparatus 200 and the application A1 is further abnormally disconnected from the state shown in FIG. In this case, the transmission / reception management unit 210 cannot transmit packets to all the applications A1 to A3.

Therefore, the buffer management unit 250 updates the accumulation permission ratio in the table T1. Here again, the buffer management unit 250 calculates the accumulation permission ratio by dividing the communication quality of each application by the total value of the communication quality of the applications for which communication is disconnected.

In the example shown in FIG. 7, the communication quality of application A1 is “1”, the communication quality of application A2 is “0”, and the communication quality of application A3 is “2”. Therefore, the buffer management unit 250 changes the accumulation permission ratio for the application A1 in the table T1 from “0%” to “33%” as indicated by B4. Further, as shown in B5, the buffer management unit 250 changes the accumulation permission ratio for the application A3 in the table T1 from “100%” to “66%”.

Since the accumulation permission ratio for the application A1 is changed to “33%”, the buffer management unit 250 accumulates the packets for the application A1 in the buffer memory 270. The buffer management unit 250 overwrites the packet for the application A3 stored in the buffer memory 270 with the packet for the application A1. Eventually, packets for the application A1 are accumulated in the buffer memory 270 to 33% of the storage capacity of the buffer memory 270.

FIG. 8 shows a case where communication between the database management apparatus 200 and the application A3 is further restored from the state shown in FIG. In this case, the transmission / reception management unit 210 cannot transmit packets to the applications A1 and A2, but can transmit packets to the application A3.

Therefore, the packet for the application A3 stored in the buffer memory 270 is transmitted to the application A3 by the transmission / reception management unit 210, and the transmitted packet is deleted from the buffer memory 270.

Further, the buffer management unit 250 updates the accumulation permission ratio in the table T1. Here again, the buffer management unit 250 calculates the accumulation permission ratio by dividing the communication quality of each application by the total value of the communication quality of the applications for which communication is disconnected.

In the example illustrated in FIG. 8, the buffer management unit 250 changes the accumulation permission ratio for the application A1 in the table T1 from “33%” to “100%” as illustrated in B6. Further, as indicated by B7, the buffer management unit 250 changes the accumulation permission ratio for the application A3 in the table T1 from “66%” to “0%”.

When the packet for the application A3 is transmitted to the application A3, the memory area in the buffer memory 270 is released. Therefore, the buffer management unit 250 accumulates packets for the application A1 in the buffer memory 270. Thus, packets for the application A1 continue to be accumulated in the buffer memory 270 until communication between the database management apparatus 200 and the application A1 is restored.

As described above, when only communication with one application is disconnected, the buffer management unit 250 stores the query result regarding the application whose communication is disconnected in the buffer memory 270. Further, when communication with two or more applications is disconnected, the buffer management unit 250 adjusts the accumulation permission ratio for each application in the buffer memory 270. Specifically, the buffer management unit 250 increases the storage permission ratio as the communication quality is lower. As a result, a large number of query results with many transmission retries can be stored in the buffer memory 270, so that the availability of the entire system can be improved.

FIG. 9 is a flowchart showing details of the state monitoring process according to the first embodiment. The state monitoring process shown in FIG. 9 is periodically executed by the communication quality determination unit 260 and the buffer management unit 250.

First, the communication quality determination unit 260 determines whether or not communication with the application terminal 100 is possible (S10). When determining that communication with the application terminal 100 is possible, the communication quality determination unit 260 subtracts 1 from the count value corresponding to the connection source ID of the application terminal 100 in the table T1 (FIG. 3) (S11).

Next, the communication quality determination unit 260 determines whether or not the count value is 0 (S12). If the communication quality determination unit 260 determines that the count value is not 0, the process proceeds to S15 described later. On the other hand, when determining that the count value is 0, the communication quality determination unit 260 subtracts 1 from the communication quality in the table T1 (S13), and sets the count value in the table T1 to the maximum value (S14).

Thereafter, the buffer management unit 250 calculates the accumulation permission ratio based on the communication quality shown in the table T1 (S15). As described above, when the communication with the application is disconnected, the buffer management unit 250 sets the communication quality corresponding to the connection source ID of the application to the total value of the communication quality of all the applications that are disconnected. The accumulation permission ratio is calculated by dividing by. The buffer management unit 250 writes the calculated accumulation permission ratio in the table T1, and ends the processing according to this flowchart.

On the other hand, if the communication quality determination unit 260 determines in S10 that communication with the application terminal 100 is not possible, 1 is added to the count value corresponding to the connection source ID of the application terminal 100 in the table T1 (FIG. 3). (S16).

Next, the communication quality determination unit 260 determines whether or not the count value is the maximum value (S17). If the communication quality determination unit 260 determines that the count value is not the maximum value, the communication quality determination unit 260 advances the process to S15 described above. On the other hand, when the communication quality determination unit 260 determines that the count value is the maximum value, 1 is added to the communication quality in the table T1 (S18), and the count value in the table T1 is set to 0 (S19). Thereafter, the communication quality determination unit 260 advances the process to S15 described above.

Through the above processing, the communication quality determination unit 260 can determine the communication quality for each application. Note that the communication quality determination processing by the communication quality determination unit 260 is not limited to the flowchart shown in FIG. For example, the communication quality determination unit 260 may determine the communication quality based on an average disconnection interval or an average reconnection interval of communication with the application. The average disconnection interval is an average time from when the communication with the application is disconnected until the next disconnection with the application, but is not limited thereto. For example, the average disconnection interval may be an average frequency at which communication with an application in a unit time is disconnected. The average reconnection interval is an average time from when the communication with the application is restored until the next communication with the application is restored, but is not limited thereto. For example, the average reconnection interval may be an average frequency at which communication with an application in a unit time is restored.

FIG. 10 is a flowchart showing details of the normal cutting process according to the first embodiment. The normal disconnection process shown in FIG. 10 is executed by the buffer management unit 250 and the transmission / reception management unit 210 when the application terminal 100 terminates the application.

First, the buffer management unit 250 deletes the entry corresponding to the application to be terminated from the buffer memory 270 (S20). At this time, the buffer management unit 250 also deletes the entry corresponding to the application to be ended from the table T1. Next, the transmission / reception management unit 210 disconnects communication with the application terminal 100 (S21), and ends the processing according to this flowchart.

FIG. 11 is a flowchart showing details of the query result entry receiving process according to the first embodiment. The query result entry receiving process shown in FIG. 11 is executed when a query result entry is input from the query execution unit 240 to the buffer management unit 250. The query result entry is represented by (x, e, r). x is query identification information for identifying a query. e is a record number. r is a query result record.

First, the buffer management unit 250 refers to the “connection state” in the table T1, and determines whether or not the application terminal 100 related to the query result entry input from the query execution unit 240 is “connected” (S30). . If the buffer management unit 250 determines that the application terminal 100 related to the query result entry input from the query execution unit 240 is “connected”, the buffer management unit 250 creates a packet using the query result entry, and the created packet is stored in the buffer memory. It memorize | stores in 270 (S31). Details of the packet creation process will be described later. Thereafter, the buffer management unit 250 ends the processing according to this flowchart.

On the other hand, in S30, when the buffer management unit 250 determines that the application terminal 100 related to the query result entry input from the query execution unit 240 is not “connected”, the entry indicating “abnormal disconnection” in the table T1. It is determined whether or not there is a plurality (S32).

When the buffer management unit 250 determines that there are a plurality of entries that are “being abnormally disconnected” in the table T1, the buffer management unit 250 refers to the “communication quality” in the table T1 and relates to the query result entry input from the query execution unit 240. It is determined whether “communication quality” is “2” or more (S33). When the buffer management unit 250 determines that the “communication quality” related to the query result entry input from the query execution unit 240 is “2” or higher, the buffer management unit 250 executes a query result error indicating that the query result entry cannot be held. Is output to the unit 240 (S34), and the processing according to this flowchart is terminated.

On the other hand, in S32, when the buffer management unit 250 does not determine that there are a plurality of entries that are “being abnormally disconnected” in the table T1, the process proceeds to S35 described later. In S33, when the buffer management unit 250 determines that the “communication quality” related to the query result entry input from the query execution unit 240 is less than “2”, the process proceeds to S35 described later.

In S35, the buffer management unit 250 refers to the table T1, and determines whether or not the “buffer usage” related to the query result entry input from the query execution unit 240 has reached the “accumulation permission ratio” (S35). ). If the buffer management unit 250 determines that the “buffer usage” related to the query result entry input from the query execution unit 240 has reached the “accumulation permission ratio”, the buffer management unit 250 indicates that the buffer memory 270 is full. A buffer full error is output to the query execution unit 240 (S36), and the processing according to this flowchart ends.

On the other hand, if the buffer management unit 250 determines in S35 that the “buffer usage” related to the query result entry input from the query execution unit 240 has not reached the “accumulation permission ratio”, the buffer memory 270 has an empty space. It is determined whether or not there is (S37). When the buffer management unit 250 determines that the buffer memory 270 is free, the buffer management unit 250 creates a packet using the query result entry, and stores the created packet in the buffer memory 270 (S38). Thereafter, the buffer management unit 250 updates the “buffer usage” in the table T1 (S39), and ends the processing according to this flowchart.

On the other hand, if the buffer management unit 250 determines in S37 that there is no free space in the buffer memory 270, it creates a packet using the query result entry, and overwrites the created packet with other entries stored in the buffer memory 270. (S40). However, as described above, there are cases where overwriting cannot be performed, for example, when the accumulation permission ratio shown in the table T1 is “0%”. Thereafter, the buffer management unit 250 updates the “buffer usage” in the table T1 (S39), and ends the processing according to this flowchart.

FIG. 12 is a flowchart showing details of the packet creation processing according to the first embodiment. The packet creation process illustrated in FIG. 12 is executed by the buffer management unit 250 in, for example, S31, S38, and S40 in FIG.

First, the buffer management unit 250 determines whether or not the query result entry received from the query execution unit 240 is the last entry of the query (S50). When the buffer management unit 250 determines that the query result entry received from the query execution unit 240 is the last entry of the query, the buffer management unit 250 determines that the packet is based on the query result entry received from the query execution unit 240 and the query result entry set. Is generated (S51). The query result entry set is a set of query result entries received from the query execution unit 240. As described above, the header information input from the transmission / reception management unit 210 is added to the packet generated by the buffer management unit 250. Thereafter, the buffer management unit 250 ends the processing according to this flowchart.

On the other hand, in S50, when the buffer management unit 250 determines that the query result entry received from the query execution unit 240 is not the last entry of the query, the size of the packet to be generated is the maximum determined by the packet size determination unit 231. It is determined whether or not the packet size is exceeded (S52). Here, the size of the packet to be generated is the sum of the size of the query result entry received from the query execution unit 240, the size of the query result entry set, and the size of the header information. If it is determined that the size of the packet to be generated exceeds the maximum packet size, the buffer management unit 250 generates a packet based on the query result entry set (S53). Thereafter, the buffer management unit 250 ends the processing according to this flowchart.

On the other hand, if the buffer management unit 250 determines in S52 that the size of the packet to be generated does not exceed the maximum packet size, it adds the query result entry received from the query execution unit 240 to the query result entry set (S54). Then, the process according to this flowchart is terminated.

FIG. 13 is a flowchart showing details of error processing according to the first embodiment. The error processing shown in FIG. 13 is executed by the buffer management unit 250 and the transmission / reception management unit 210 when a buffer erasure request is input from the query execution unit 240 to the buffer management unit 250. The buffer erasure request is input from the query execution unit 240 to the buffer management unit 250 when an error occurs in the query execution unit 240. The buffer erase request is represented by (x, z). x is query identification information for identifying a query. z is the error content.

First, the buffer management unit 250 acquires the query identification information x from the buffer erasure request (x, z) (S61). Next, the buffer management unit 250 deletes all entries related to the acquired query identification information x from the buffer memory 270 (S62).

Thereafter, the buffer management unit 250 refers to the table T1 and determines whether or not the connection state of the connection source of the query whose entry has been deleted is “connected” (S63). When the buffer management unit 250 determines that the connection state of the connection source of the query from which the entry has been deleted is “connected”, the transmission / reception management unit 210 causes an error in the application terminal 100 related to the query from which the entry has been deleted. Information (x, z) is transmitted (S64), and the processing according to this flowchart is terminated.

On the other hand, in S63, when the buffer management unit 250 determines that the connection state of the connection source of the query whose entry has been deleted is not “connected”, the buffer management unit 250 stores the error information (x, z) in the buffer memory 270 ( S65), the process according to this flowchart is terminated.

FIG. 14 is a flowchart showing details of the transmission continuation processing according to the first embodiment. The transmission continuation process shown in FIG. 14 is executed when the database management apparatus 200 receives a transmission continuation request from the application terminal 100. When the communication between the application terminal 100 and the database management apparatus 200 is restored, the application terminal 100 transmits a transmission continuation request to the database management apparatus 200 in order to request retransmission of the query result whose transmission has been interrupted. To do. The transmission continuation request is represented by (x, E). x is query identification information for identifying a query. E is a record number.

First, the buffer management unit 250 determines whether an entry larger than the record number E included in the transmission continuation request (x, E) is stored in the buffer memory 270 (S70). When the buffer management unit 250 determines that an entry larger than the record number E is stored in the buffer memory 270, the transmission / reception management unit 210 reads all entries having a record number larger than the record number E from the buffer memory 270. And transmitted to the application terminal 100 (S71). Thereafter, the transmission / reception management unit 210 deletes the transmitted entry from the buffer memory 270 and ends the processing according to this flowchart.

On the other hand, when the buffer management unit 250 determines in S70 that the entry larger than the record number E is not stored in the buffer memory 270, error information (x, z) regarding the query identification information x is stored in the buffer memory 270. It is determined whether it is stored (S72). When the buffer management unit 250 determines that the error information (x, z) for the query identification information x is stored in the buffer memory 270, the transmission / reception management unit 210 receives the error information (x, z) from the buffer memory 270. Is transmitted to the application terminal 100 (S73). Thereafter, the transmission / reception management unit 210 deletes the transmitted error information (x, z) from the buffer memory 270, and ends the processing according to this flowchart.

On the other hand, when the buffer management unit 250 determines in S72 that the error information (x, z) for the query identification information x is not stored in the buffer memory 270, the transmission / reception management unit 210 accepts the transmission continuation request. Is notified to the application terminal 100 (S74), and the processing according to this flowchart is terminated.

FIG. 15 is a flowchart showing details of the query processing according to the first embodiment. The query processing illustrated in FIG. 15 is executed by the query execution unit 240 when the database management apparatus 200 receives a query from the application terminal 100. The query is represented by (x, q). x is query identification information for identifying a query. q is a query content.

First, the query execution unit 240 sets 0 to the record number e (S81). Next, the query execution unit 240 generates a record r indicating the content of the query result based on the query content q (S82), and adds 1 to the record number e (S83).

Thereafter, the query execution unit 240 determines whether or not the record r is normally generated (S84). When the query execution unit 240 determines that the record r has not been generated normally, the query execution unit 240 outputs a buffer deletion request due to an internal error to the buffer management unit 250 (S85), and ends the processing according to this flowchart.

On the other hand, in S84, when the query execution unit 240 determines that the record r is normally generated, the query execution unit 240 outputs the query result entry (x, e, r) to the buffer management unit 250 (S86). Thereafter, the query execution unit 240 determines whether or not an error is output from the buffer management unit 250 to the query execution unit 240 (S87). For example, as described above, the buffer management unit 250 outputs an error to the query execution unit 240 in S34 and S36 illustrated in FIG.

In S87, if the query execution unit 240 does not determine that an error has been output from the buffer management unit 250 to the query execution unit 240, the query execution unit 240 determines whether or not the processing based on the query content q has been completed (S88). When the query execution unit 240 determines that the process based on the query content q is completed, the query execution unit 240 ends the process according to this flowchart. Conversely, if the query execution unit 240 determines that the process based on the query content q has not been completed, it returns the process to S82 described above.

On the other hand, if the query execution unit 240 determines in S87 that an error has been output from the buffer management unit 250 to the query execution unit 240, the query execution unit 240 determines whether or not a predetermined time has elapsed since the error was output (S89). . If the query execution unit 240 determines that a predetermined time has elapsed since the error was output, the query execution unit 240 outputs a buffer erase request due to a timeout error to the buffer management unit 250 (S90), and ends the processing according to this flowchart.

On the other hand, if the query execution unit 240 determines in S89 that the predetermined time has not elapsed since the error was output, the entry for the query identification information x is overwritten with another query result entry in the buffer memory 270. It is determined whether or not (S91). When the query execution unit 240 determines that the entry for the query identification information x has been overwritten by another query result entry, the query execution unit 240 returns the record number e to the point where it has not been overwritten (S92), and returns the process to S82 described above. .

On the other hand, in S91, when the query execution unit 240 determines that the entry for the query identification information x is not overwritten by another query result entry, the process returns to S86 described above.

As described above, the database management system 10 according to the first embodiment includes the transmission / reception management unit 210, the query execution unit 240, the buffer management unit 250, and the communication quality determination unit 260. The transmission / reception management unit 210 receives a query from the application terminal 100 that executes the application, reads a query result that is data to be searched for the query from the buffer memory 270, and transmits the query result to the application terminal 100. The query execution unit 240 acquires a query result by executing a process based on the query received by the transmission / reception management unit 210. The communication quality determination unit 260 determines the communication quality (see FIG. 3) for each application. When the communication with the application terminal 100 is disconnected, the buffer management unit 250 determines whether or not the query result acquired by the query execution unit 240 is stored in the buffer memory 270 by the communication quality determination unit 260. Determine based on communication quality. Accordingly, the database management system 10 can retransmit the query result data according to the convenience of the application even when the network connection environment of the database management system 10 is unstable.

The buffer memory 270 is a memory that can be accessed simultaneously by the buffer management unit 250 and the transmission / reception management unit 210. Therefore, it is not necessary to separately provide a transmission buffer dedicated to the transmission / reception management unit 210 in the kernel space of the database management apparatus 200. As a result, the memory can be saved, and the accumulation permission ratio for each application in the buffer memory 270 can be set flexibly.

Further, the buffer management unit 250 adds header information necessary for communication to the query result acquired by the query execution unit 240, and stores the query result packet to which the header information is added in the buffer memory 270. The transmission / reception management unit 210 reads the query result packet from the buffer memory 270 and transmits the read query result packet to the application terminal 100. Accordingly, the transmission / reception management unit 210 can transmit the query result packet to the application terminal 100 without processing the packet.

(Second Embodiment)
Next, a second embodiment will be described. In the first embodiment, the buffer management unit 250 increases the accumulation permission ratio as the communication quality is worse. In contrast, in the second embodiment, the buffer management unit 250 decreases the accumulation permission ratio as the communication quality is lower. As a result, it is possible to prevent the buffer memory 270 from being occupied exclusively by an unstable communication line query result. Details of the second embodiment will be described below.

In the second embodiment, when only communication with one application is disconnected, the buffer management unit 250 stores a query result related to the application whose communication is disconnected in the buffer memory 270. On the other hand, when communication with two or more applications is disconnected, the buffer management unit 250 adjusts the accumulation permission ratio for each application in the buffer memory 270. Specifically, the buffer management unit 250 decreases the accumulation permission ratio as the communication quality is lower.

The communication quality is any value from “0” to “3”, but unlike the first embodiment, the larger the value, the better the quality of the communication line. For example, “3” indicates that the communication quality is the best and abnormal disconnection hardly occurs. On the other hand, “0” indicates that the communication quality is the worst and abnormal disconnection is likely to occur. The communication quality is determined by the communication quality determination unit 260.

The buffer management unit 250 sets a storage permission ratio of the buffer memory 270 for a connection source whose communication quality is “1” or higher. The buffer management unit 250 calculates the accumulation permission ratio by dividing the communication quality of each application by the total value of the communication quality of the applications that have been disconnected. The buffer management unit 250 writes the calculated accumulation permission ratio in the table T1.

As described above, in the second embodiment, the buffer management unit 250 decreases the accumulation permission ratio as the communication quality is worse. As a result, it is possible to prevent the buffer memory 270 from being occupied exclusively by an unstable communication line query result.

(Third embodiment)
Next, a third embodiment will be described. In the first embodiment and the second embodiment, the buffer management unit 250 calculates the accumulation permission ratio based on the communication quality for each application. On the other hand, in the third embodiment, the query execution unit 240 predicts the data amount of the data representing the query result, and calculates the accumulation permission ratio based on the predicted data amount. Specifically, the query execution unit 240 decreases the accumulation permission ratio as the predicted data amount increases. As a result, the average consumption of the buffer memory 270 can be reduced. Details of the third embodiment will be described below.

FIG. 16 is a diagram illustrating an example of a table T2 according to the third embodiment. In the third embodiment, the buffer management unit 250 determines the accumulation permission ratio using a table T2 shown in FIG. 16 instead of the table T1 shown in FIG. The table T2 is a table in which the connection source ID, the predicted data amount, the connection state, the accumulation permission ratio, the buffer usage amount, and the count value are associated with each other.

The predicted data amount is information indicating a predicted value of the data amount of data representing the query result. The predicted data amount is any value from “0” to “3”, and the smaller the value, the larger the predicted data amount. For example, in the case of a query with only an aggregate function or an analysis function, the predicted data amount is “3”. In the case of a query with “GROUP BY” attached to an aggregate function or analytic function, the predicted data amount is “2”. In the case of a query with many “WHERE” phrases, the predicted data amount is “1”. In the case of other queries (for example, scan), the predicted data amount is “0”. Since the items other than the predicted data amount in the table T2 are the same as those in the table T1, the description thereof is omitted.

The connection source ID is 6 bytes, the predicted data amount is 2 bits, the connection state is 1 bit, the storage permission ratio is 6 bits (upper limit: 100), and the buffer usage is 6 bits (upper limit) : 100) and the count value is 2 bytes. Therefore, one entry in the table T2 is composed of a total of 10 bytes.

FIG. 17 is a flowchart showing details of the query result entry receiving process according to the third embodiment. The query result entry receiving process shown in FIG. 17 is executed when a query result entry is input from the query execution unit 240 to the buffer management unit 250. The query result entry is represented by (x, e, r). x is query identification information for identifying a query. e is a record number. r is a query result record.

First, the buffer management unit 250 refers to the “connection state” in the table T2, and determines whether or not the application terminal 100 related to the query result entry input from the query execution unit 240 is “connected” (S100). . If the buffer management unit 250 determines that the application terminal 100 related to the query result entry input from the query execution unit 240 is “connected”, the buffer management unit 250 creates a packet using the query result entry, and the created packet is stored in the buffer memory. The data is stored in 270 (S101). Thereafter, the buffer management unit 250 ends the processing according to this flowchart.

On the other hand, in S100, if the buffer management unit 250 determines that the application terminal 100 related to the query result entry input from the query execution unit 240 is not “connected”, the entry indicating “abnormal disconnection” in the table T2 It is determined whether or not there is a plurality (S102).

When the buffer management unit 250 determines that there are a plurality of entries that are “being abnormally disconnected” in the table T2, the query result entry input from the query execution unit 240 with reference to the “predicted data amount” in the table T2 It is determined whether or not the “predicted data amount” relating to “0” is “0” (S103). When the buffer management unit 250 determines that the “predicted data amount” related to the query result entry input from the query execution unit 240 is “0”, a query execution error indicating that the query result entry cannot be held is executed. The data is output to the unit 240 (S104), and the processing according to this flowchart is terminated.

On the other hand, in S102, if the buffer management unit 250 does not determine that there are a plurality of entries that are “being abnormally disconnected” in the table T2, the process proceeds to S105 described later. In S103, when the buffer management unit 250 determines that the “predicted data amount” related to the query result entry input from the query execution unit 240 is not “0”, the buffer management unit 250 proceeds to S105 described later.

In S105, the buffer management unit 250 refers to the table T2, and determines whether or not the “buffer usage” related to the query result entry input from the query execution unit 240 has reached the “accumulation permission ratio” (S105). ). If the buffer management unit 250 determines that the “buffer usage” related to the query result entry input from the query execution unit 240 has reached the “accumulation permission ratio”, the buffer management unit 250 indicates that the buffer memory 270 is full. A buffer full error is output to the query execution unit 240 (S106), and the processing according to this flowchart ends.

On the other hand, in S105, when the buffer management unit 250 determines that the “buffer usage amount” has not reached the “accumulation permission ratio”, the buffer management unit 250 determines whether or not the buffer memory 270 has an empty space (S107). When the buffer management unit 250 determines that the buffer memory 270 is free, the buffer management unit 250 creates a packet using the query result entry, and stores the created packet in the buffer memory 270 (S108). Thereafter, the buffer management unit 250 updates the “buffer usage” in the table T2 (S109), and ends the processing according to this flowchart.

On the other hand, if the buffer management unit 250 determines in S107 that the buffer memory 270 has no free space, it creates a packet using the query result entry, and overwrites the created packet with another entry stored in the buffer memory 270. (S110). However, as described above, there are cases where overwriting cannot be performed, for example, when the accumulation permission ratio shown in the table T2 is “0%”. Thereafter, the buffer management unit 250 updates the “buffer usage” in the table T2 (S109), and ends the processing according to this flowchart.

FIG. 18 is a flowchart showing details of query processing according to the third embodiment. The query processing shown in FIG. 18 is executed by the query execution unit 240 when the database management apparatus 200 receives a query from the application terminal 100. The query is represented by (x, q). x is query identification information for identifying a query. q is a query content.

First, the query execution unit 240 calculates a storage permission ratio based on the type of query and the query search condition (S120). Specifically, the query execution unit 240 determines whether the predicted data amount of the query result is “0” to “3”. As described above, in the case of a query with only an aggregate function or an analysis function, the predicted data amount is “3”. In the case of a query with “GROUP BY” attached to an aggregate function or analytic function, the predicted data amount is “2”. In the case of a query with many “WHERE” phrases, the predicted data amount is “1”. In the case of other queries (for example, scan), the predicted data amount is “0”.

Further, the query execution unit 240 calculates the accumulation permission ratio by dividing the predicted data amount by the total value of the predicted data amounts of the applications for which communication is disconnected. The query execution unit 240 writes the calculated accumulation permission ratio in the table T2.

The processing from S121 to S132 in FIG. 18 is the same as the processing from S81 to S92 in FIG. For this reason, the details of the processing from S121 to S132 are omitted.

As described above, in the third embodiment, the query execution unit 240 predicts the data amount of data representing the query result. The buffer management unit 250 determines whether or not to store the query result acquired by the query execution unit 240 in the buffer memory 270 based on the data amount predicted by the query execution unit 240. As a result, the average consumption of the buffer memory 270 can be reduced.

According to at least one embodiment described above, the database management system 10 includes the transmission / reception management unit 210, the query execution unit 240, and the buffer management unit 250. The transmission / reception management unit 210 receives a query from the application terminal 100 that executes the application, reads a query result that is data to be searched for the query from the buffer memory 270, and transmits the query result to the application terminal 100. The query execution unit 240 acquires a query result by executing a process based on the query received by the transmission / reception management unit 210. The buffer management unit 250 determines whether or not to store the query result acquired by the query execution unit 240 in the buffer memory 270 when communication with the application terminal 100 is disconnected, based on an evaluation value related to communication with the application. Judgment. Accordingly, the database management system 10 can retransmit the query result data according to the convenience of the application even when the network connection environment of the database management system 10 is unstable.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 ... Database management system, 100 ... Application terminal, 110 ... Application execution part, 120 ... Packet size determination part, 200 ... Database management apparatus, 210 ... Transmission / reception management part, 230 ... Connection management part, 231 ... Packet size determination part, 240 ... Query execution unit, 250 ... Buffer management unit, 260 ... Communication quality determination unit, 270 ... Buffer memory, 280 ... Storage unit

Claims (9)

1. A transmission / reception management unit that receives a query from an application terminal that executes an application, reads a query result that is data to be searched for the query from a buffer memory, and transmits the query result to the application terminal;
   A query execution unit that acquires the query result by executing processing based on the query received by the transmission / reception management unit;
   A buffer for determining whether to store the query result acquired by the query execution unit in the buffer memory based on an evaluation value related to communication with the application when communication with the application terminal is disconnected The management department,
   A database management device comprising:
2. The evaluation value further includes a communication quality determination unit that determines communication quality for each application,
   The buffer management unit determines whether to store the query result acquired by the query execution unit in the buffer memory based on the communication quality determined by the communication quality determination unit. Database management device.
3. The database management device according to claim 2, wherein the communication quality determination unit determines the communication quality based on an average disconnection interval or an average reconnection interval of communication with the application.
4. The query execution unit predicts a data amount of data representing the query result as the evaluation value,
   The said buffer management part determines whether the said query result acquired by the said query execution part is memorize | stored in the said buffer memory based on the said data amount estimated by the said query execution part. Database management device.
5. The database management device according to claim 4, wherein the query execution unit predicts the data amount based on a type of the query and a search condition of the query.
6. The buffer memory is a memory that the buffer management unit and the transmission / reception management unit can access simultaneously,
   The buffer management unit adds header information necessary for communication to the query result acquired by the query execution unit, and stores the query result to which the header information is added in the buffer memory,
   The database management apparatus according to any one of claims 1 to 5, wherein the transmission / reception management unit reads the query result from the buffer memory and transmits the read query result to the application terminal.
7. A packet size determining unit that performs negotiation with the application terminal and determines a maximum packet size that can be used between the database management device and the application terminal;
   The buffer management unit generates a packet in which the header information is added to one or more records of the query result within a range that fits the maximum packet size determined by the packet size determination unit, and the generated packet The database management device according to claim 6, wherein: is stored in the buffer memory.
8. An application terminal that executes the application;
   A database management device connected to the application terminal,
   The database management device includes:
   A transmission / reception management unit that receives a query from the application terminal, and reads a query result that is data to be searched for the query from a buffer memory,
   A query execution unit that acquires the query result by executing processing based on the query received by the transmission / reception management unit;
   A buffer for determining whether to store the query result acquired by the query execution unit in the buffer memory based on an evaluation value related to communication with the application when communication with the application terminal is disconnected The management department,
   A database management system comprising:
9. The transmission / reception management unit receives a query from an application terminal that executes an application, reads a query result that is data to be searched for the query from a buffer memory, and transmits the query result to the application terminal.
   The query execution unit acquires the query result by executing a process based on the query received by the transmission / reception management unit,
   Whether or not the buffer management unit stores the query result acquired by the query execution unit in the buffer memory when communication with the application terminal is disconnected, as an evaluation value related to communication with the application Judgment based on database management method.

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