JPH05120348A - Control system for buffer memory - Google Patents

Abstract

PURPOSE:To provide the control system for buffer memory which can reduce the number of times for inputting/outputting between a main storage device and a second-order storage device in the case of a retrieval processing in at a data base system and can shorten the response time of the retrieval processing without using an I/O buffer storing an index block having the high possibility of use after a current time point for reading data. CONSTITUTION:A conditional expression is analyzed so as to decide a retrieval process (S1), required data are decided so as to execute retrieval (S2) and when there is the I/O buffer storing the required data and these data are indexes, a value enlarging the frequency of remaining the data in the main storage device of this I/O buffer is set (S10). This I/O buffer is relinked to the end of a chain (S11) and when there is no I/O buffer storing the required data, the data are read in an empty I/O buffer (S9). When there is no empty I/O buffer, the data are read in the I/O buffer at the head of the chain (S9) and the operation is continued.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a buffer storage control system, and more particularly to a buffer storage control system used for input / output between a main storage device and a secondary storage device of an index file in a search process of a database system.

[0002]

2. Description of the Related Art A conventional buffer storage control system manages an I / O buffer used for input / output between a main storage device and a secondary storage device, and uses an I / O used for reading arbitrary data. When deciding the buffer, the I / O buffer is used in the oldest order in the LRU control method. For example, when searching an index having a tree structure shown in FIG. The lower index blocks will be read in order from the block. At this time,
Since the number of index blocks at the same level of the index decreases as the index level increases (n1>n2> n3), the probability of reading any block increases as the index level increases (1 / n1 <1 / n2 <1 / n3)
However, when reading this index, the I / O buffer for data reading was determined without considering the index level.

[0003]

When the conventional buffer storage control method described above is applied to search an index having a tree structure, an I / O buffer for data reading is used without considering the level of the index. Since it has been decided, it is unavoidable to use the I / O buffer that contains the index block that is likely to be used after the present time, and unnecessary input processing may be required. There is a problem.

An object of the present invention is not to use an I / O buffer containing an index block, which is likely to be used after the present time, for reading data, and a main storage device in a search process of a database system. Another object of the present invention is to provide a buffer storage control method capable of reducing the number of inputs and outputs between the secondary storage device and the response time of search processing.

[0005]

A buffer storage control system of the present invention is a buffer storage control system used for input / output between a main storage device and a secondary storage device of an index file in a search process of a database system. , The specified conditional expression is analyzed to determine the search procedure, the data required for performing the search is determined according to the determined search procedure, the search is performed, and it is determined whether the search is completed. ,
If the search is not completed, it is determined whether or not there is an I / O buffer containing the required data,
If there is an I / O buffer containing the required data and this data is an index, set a value that increases the frequency of leaving this I / O buffer in the main storage device according to the level of the index. , The I / O buffer that has read the data in which this increased value has been read is connected to the end of the chain of this I / O buffer, a search is performed according to the search procedure, and the I / O containing the required data is entered. If the O buffer does not exist, then it is determined whether or not there is a free I / O buffer next. If there is a free I / O buffer, the secondary I / O buffer is added to the secondary I / O buffer. The required data is read from the storage device, and the operation is taken over when there is an I / O buffer containing the required data. If there is no empty I / O buffer, the I / O buffer is read. It is determined whether the head I / O buffer of the chain of files is available, and if the head I / O buffer is available, the operation is taken over to read the necessary data from the secondary storage device, I / at the beginning
If the O buffer is not available, the frequency of leaving the head I / O buffer in the main storage device is reduced to reduce the head I / O buffer.
This is a configuration in which the O buffer is connected to the end of the chain of I / O buffers and the operation is continued to determine again whether or not the first I / O buffer in the chain of I / O buffers is available.

[0006]

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

FIG. 1 is a flow chart of one embodiment of the present invention.
3 is a block diagram showing the configuration of the secondary storage device.

That is, in the example of FIG. 3, the secondary storage device 1
Stores the index 2 and the data record 3 of the item A, the number of stages of the index 2 of the item A is "3", and each index block has four values and the record number having this value, or , Stores a set of pointers to the lower index blocks. Further, the data block 3 stores two records each.

4 to 14 are explanatory views for explaining the contents of the I / O buffer and the transition of the management state when the processes of the embodiment are sequentially performed.

1 to 14, the conditional expression "item A = 20 OR item A" is applied to the secondary storage device.
The process of obtaining the records with the record numbers R2 and R3 that satisfy "= 30" will be described. The operation flow is as shown in FIG. 1. (1) Analysis of conditional expression.

In step (hereinafter referred to as S) 1, the conditional expression "item A = 20 OR item A = 30" is analyzed. As a result, the index of item A is searched by "20", and then item A is searched.
Of the conditional expression “item A = 20O” by calculating the logical sum of the result of searching the index of item A with “20” and the result of searching the index of item A with “20” and the index of item A with “30”.
It is found that a record satisfying R item A = 30 "is obtained, and the process proceeds to S2. (2) The index of item A is searched by" 20 ".

In S2, it is decided to obtain the index block 1-1 to search the index of item A by "20".
The process proceeds to S3.

Since the search is not completed in S3, S4 is executed.
Proceed to. Find index block 1-1.

At S4, it is determined whether or not there is an I / O buffer containing the index block 1-1.

FIG. 4 shows the initial state of the main memory device, which is an I / O that is empty and contains the index block 1-1.
Since there is no O buffer, the process proceeds to S5.

In S5, it is determined whether or not there is an empty I / O buffer in the main storage device. Since there is an empty I / O buffer as shown in FIG. 4, the process proceeds to S9.

In S9, the index block 1 is read from the secondary storage device.
-1 is read into the empty I / O buffer, and the process proceeds to S10.

In S10, the frequency of leaving the index block 1-1 in the main memory of the I / O buffer is set.
Here, since the index level of the item A is three levels and the index block 1-1 is the highest index, it is set to "2" and the process proceeds to S11.

In S11, the I / O buffer containing the index block 1-1 is connected to the end of the chain of I / O buffers and the process proceeds to S2. The management state of the I / O buffer at this time is shown in FIG.

At S2, the value "1" of the index block 1-1
It is determined to obtain the index block 2-1 indicated by the 0 "pointer, and the process proceeds to S3.

Since the search is not completed in S3, S4 is executed.
Proceed to. Find index block 2-1.

At S4, since there is no I / O buffer containing the index block 2-1 as shown in FIG.
The process proceeds to 5.

At S5, since there is an empty I / O buffer as shown in FIG. 5, the process proceeds to S9.

In S9, the index block 2 is read from the secondary storage device.
-1 is read into the empty I / O buffer, and the process proceeds to S10.

In S10, since the index block 2-1 is the index of the second stage, the frequency to be left in the main memory is set to "1", and the process proceeds to S11.

In S11, the I / O buffer containing the index block 2-1 is reconnected to the end of the chain of I / O buffers and the process proceeds to S2. FIG. 6 shows the management state of the I / O buffer at this point.

At S2, the value "10" of the index block 2-1 is obtained.
It is determined that the index block 3-1 indicated by the pointer is obtained, and the process proceeds to S3.

Since the search is not completed in S3, S4 is executed.
Proceed to. Find index block 3-1.

In S4, the index block 3 is generated as shown in FIG.
Since there is no I / O buffer containing -1, the process proceeds to S5.

At S5, since there is an empty I / O buffer as shown in FIG. 6, the process proceeds to S9.

In S9, the index block 3 is read from the secondary storage device.
-1 is read into the empty I / O buffer, and the process proceeds to S10.

Since the index block 3-1 is the index of the first stage in S10, the frequency to be left in the main memory is set to "0", and the process proceeds to S11.

In S11, the I / O buffer containing the index block 3-1 is connected to the end of the chain of I / O buffers, and the process proceeds to S2. The management state of the I / O buffer at this time is shown in FIG.

At S2, the value "20" of the index block 3-1.
It is determined that the data block 1 is to be obtained in order to obtain the record indicated by the record number R2, and the process proceeds to S3.

Since the search is not completed in S3, S4 is executed.
Proceed to. Find data block 1.

Since there is no I / O buffer containing the data block 1 in S4 as shown in FIG. 7, S5 is executed.
Proceed to.

In S5, as shown in FIG. 7, since there is no empty I / O buffer, the process proceeds to S6.

In S6, it is determined whether or not the first I / O buffer in the chain of I / O buffers is available. As shown in FIG. 7, the first I / O in the chain of I / O buffers
Since the frequency of leaving in the main memory of the buffer is "2",
The process proceeds to S7.

In S7, the frequency of leaving the main I / O buffer in the head I / O buffer of the chain of I / O buffers is reduced from "2" to "1", and the process proceeds to S8.

In S8, the head I / O buffer of the chain of I / O buffers is connected to the end of the chain of I / O buffers and the process proceeds to S6. The management state of the I / O buffer at this time is shown in FIG.

In S6, as shown in FIG. 8, since the frequency of leaving in the main storage device of the head I / O buffer of the chain of I / O buffers is "1", the process proceeds to S7.

In S7, the frequency of leaving the main I / O buffer in the head I / O buffer of the chain of I / O buffers is reduced from "1" to "0", and the process proceeds to S8.

In S8, the head I / O buffer of the chain of I / O buffers is connected to the end of the chain of I / O buffers, and the process proceeds to S6. The management state of the I / O buffer at this time is shown in FIG.

In S6, as shown in FIG. 9, since the frequency of remaining in the main storage device of the head I / O buffer of the chain of I / O buffers is "0", the process proceeds to S9.

In S9, the data block 1 is read from the secondary storage device into the I / O buffer at the head of the chain of I / O buffers, and the process proceeds to S10.

Since the data block 1 is not an index in S10, the frequency to be left in the main memory is set to "0", and S11 is set.
Proceed to.

In S11, the I / O buffer containing the data block 1 is reconnected to the end of the chain of I / O buffers, and the process proceeds to S2. FIG. 10 shows the management state of the I / O buffer at this point. (2) Search the index of item A with "30".

In S2, the index of item A is searched with "30", so it is decided to find the index block 1-1.
The process proceeds to 3.

Since the search is not completed in S3, S4 is executed.
Proceed to. Find index block 1-1.

At S4, as shown in FIG. 10, since there is an I / O buffer containing the index block 1-1,
The process proceeds to S10.

At S10, the level of the index of item A is three, and the index block 1-1 is the highest index.
The frequency of remaining in the main memory of the I / O buffer containing the index block 1-1 is set to "2", and the process proceeds to S11.

In S11, the I / O buffer containing the index block 1-1 is reconnected to the end of the chain of I / O buffers, and the process proceeds to S2. I / O at this point
The management state of the buffer is shown in FIG.

At S2, the value "10" of the index block 1-1.
It is determined that the index block 2-1 indicated by the pointer is obtained, and the process proceeds to S3.

Since the search is not completed in S3, S4 is executed.
Proceed to. Find index block 2-1.

Since there is an I / O buffer containing the index block 2-1 in S4 as shown in FIG.
The process proceeds to 10.

In S10, since the index block 2-1 is the second-stage index, the frequency to be left in the main memory is set to "1", and the process proceeds to S11.

In S11, the I / O buffer containing the index block 2-1 is reconnected to the end of the chain of I / O buffers, and the process proceeds to S2. I / O at this point
The management state of the buffer is shown in FIG.

At S2, the value "10" of the index block 2-1 is obtained.
It is determined to obtain the index block 3-1 indicated by the pointer of, and the process proceeds to S3.

Since the search is not completed in S3, S4 is executed.
Proceed to. Find index block 3-1.

At S4, since there is no I / O buffer containing the index block 3-1 as shown in FIG. 12,
The process proceeds to S5.

At S5, as shown in FIG. 12, an empty I / O
Since there is no buffer, the process proceeds to S6.

In S6, as shown in FIG. 12, since the frequency of leaving in the main memory of the head I / O buffer of the chain of I / O buffers is "0", the process proceeds to S9.

In S9, the index block 3-1 is read from the secondary storage device into the I / O buffer at the head of the chain of I / O buffers, and the process proceeds to S10.

Since the index block 3-1 is the index of the first stage in S10, the frequency to be left in the main memory is set to "0", and the process proceeds to S11.

In S11, the I / O buffer containing the index block 3-1 is reconnected to the end of the chain of I / O buffers, and the process proceeds to S2. I / O at this point
The management state of the buffer is shown in FIG.

At S2, the value "30" of the index block 3-1.
It is determined to obtain the data block 2 in order to obtain the record indicated by the record number R2, and the process proceeds to S3.

Since the search is not completed in S3, S4 is executed.
Proceed to. Find data block 2.

The same process as (2) below is performed to obtain the data block 2, and the process proceeds to S2. FIG. 14 shows the management state of the I / O buffer when the reading of the data block 2 is completed. (3) The logical sum of the result of searching the index of item A with “20” and the result of searching the index of item A with “30” is obtained.

At S2, the logical sum of the result of searching the index of item A by "20" and the result of searching the index of item A by "30" is obtained, and the conditional expression "item A = 20 OR" is obtained.
Record numbers R2 and R3 satisfying item A = 30 "
Is obtained, and the process proceeds to S3.

At S3, since the search is completed, the process is completed.

[0071]

As described above, according to the present invention, the designated conditional expression is analyzed to determine the search procedure, and the data necessary for performing the search is determined according to the determined search procedure. If there is an I / O buffer that contains the required data when the search is performed and this data is an index, the value of the frequency of leaving this I / O buffer in the main storage device increased according to the level of the index. Is set, this I / O buffer is reconnected to the end of the chain, and if there is no I / O buffer containing the required data, the next free I / O buffer is transferred from the secondary storage device. Continue the operation of reading the required data, and if there is no empty I / O buffer, read the required data if the first I / O buffer in the chain of I / O buffers is available. If the first I / O buffer is not available, the frequency of leaving the first I / O buffer in the main storage device is reduced, and the operation is continued by connecting to the end of the chain to continue the operation. The I / O buffer containing the likely index block is not used for reading data, and the number of I / O operations between the main storage device and the secondary storage device in the search processing of the database system is reduced, and the search is performed. This has the effect of shortening the response time in processing.

[Brief description of drawings]

FIG. 1 is a flow chart of one embodiment of the present invention.

FIG. 2 is a structural diagram of an index having a tree structure.

FIG. 3 is a block diagram showing a configuration of a secondary storage device.

FIG. 4 is an explanatory diagram illustrating the contents of the I / O buffer and the transition of the management state when the processes of the embodiment are sequentially performed.

FIG. 5 is an explanatory diagram illustrating the contents of the I / O buffer and the transition of the management state.

FIG. 6 is an explanatory diagram for explaining the contents of the I / O buffer and the transition of the management state.

FIG. 7 is an explanatory diagram illustrating the contents of the I / O buffer and the transition of the management state.

FIG. 8 is an explanatory diagram illustrating the contents of the I / O buffer and the transition of the management state.

FIG. 9 is an explanatory diagram illustrating the contents of the I / O buffer and the transition of the management state.

FIG. 10 is an explanatory diagram illustrating the contents of the I / O buffer and the transition of the management state.

FIG. 11 is an explanatory diagram illustrating the contents of the I / O buffer and the transition of the management state.

FIG. 12 is an explanatory diagram illustrating the contents of the I / O buffer and the transition of the management state.

FIG. 13 is an explanatory diagram illustrating the contents of the I / O buffer and the transition of the management state.

FIG. 14 is an explanatory diagram for explaining the contents of the I / O buffer and the transition of the management state.

[Explanation of symbols]

 1 Secondary Storage 2 Index of Item A 3 Data Record

Claims (1)

[Claims] 1. In a buffer storage control method used for input / output between a main storage device and a secondary storage device of an index file in a search process of a database system, a specified conditional expression is analyzed to perform a search procedure. Determine, determine the data required to perform the search according to the determined search procedure, perform the search, determine whether the search is finished, and if the search is not finished, the required data is It is determined whether or not there is an I / O buffer that contains the I / O buffer, and if there is an I / O buffer that contains the required data and this data is an index, this I / O buffer
A value is set that increases the frequency of leaving the buffer in the main memory according to the level of the index, and the I / O buffer that has read the data with this increased value is connected to the end of the chain of this I / O buffer. Then, a search is performed according to the search procedure described above, and an I /
If the O buffer does not exist, then it is determined whether or not there is a free I / O buffer next. If there is a free I / O buffer, the secondary I / O buffer is added to the secondary I / O buffer. The required data is read from the storage device, the operation is taken over when there is an I / O buffer containing the required data, and if there is no empty I / O buffer, the chain of I / O buffers I / O at the beginning of
It is determined whether or not the buffer is available, and the I / O at the head
If a buffer is available, the operation of reading the required data from the secondary storage device is taken over, and if the head I / O buffer is not available, the head I / O is transferred.
The frequency of leaving the buffer in the main memory is reduced, the head I / O buffer is connected to the end of the chain of the I / O buffer, and the head I / O of the chain of the I / O buffer is re-connected.
A control method of buffer storage, which is succeeded to an operation of determining whether or not a buffer is available.