JPS5856031A - Decision system for minimum working relation - Google Patents

Abstract

PURPOSE:To minimize the size of working relation by deciding the field constitution of the working relation, used for the inquiry processing of a relational data base system, by the use of a reference counter. CONSTITUTION:When the minimum field constitution of working relation TA for reduing relation A and storing the result is decided, the condition regarding only the original relation A is a2=5, so a minimum working relation deciding mechanism 5 requests a reference counter control mechanism 6 to subtract one from the contents of a reference counter which corresponds to a field a2. On accepting the request, the mechanism sends back the contents of a reference counter group 7 and in this case, the contents of the reference counter which corresponds to the field a2 are zero, so relation TA is allowed to have fields a1 and a2. Similarly, the field constitution of other working relation is decided.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for determining a minimum working relation in a relational tatami database system, which minimizes the size of a working relation generated as a result of a reduction or a join. .

Relational databases provide data to users in tabular format, but when a relational database system receives a user's color inquiry, it selects related rows and performs reduction or sline processing on them. to create the desired relay link.

This is provided to the user as an inquiry result. In the process of obtaining query results by combining reduction processing and synline processing, a work relation is required to temporarily store and use the reduction results or join processing. In order to improve processing efficiency in query processing, it is necessary to minimize the size of a single work relation; however, this requires reducing the field configuration to the minimum necessary and It is necessary to minimize the number of records in the file.

The present invention is intended to meet the requirements as mentioned above.
It is an object of the present invention to provide a method for determining a minimum working relation so that the field configuration of the working relation used during the inquiry processing process can be minimized to the necessary number of failures. And for that reason 1
The method for determining the minimum work relay line of the present invention determines a processing sequence including reduction processing or join processing according to inquiry information sent from the user, and also includes reduction processing in the process of executing the processing sequence.
In a relational database system that stores the results of Hashi Ei-in processing in a working relation, if there is a one-to-one correspondence with a field that appears in the above query, the number of occurrences of that field in the query is set as a common initial value. a reference counter control mechanism that has a plurality of reference counters to be processed; and a reference counter control mechanism that requests the reference counter control mechanism to change the contents of the reference counter based on the query conditions and processing sequence; A minimum working relation determining mechanism is provided which determines the field configuration of working relations for storing the results of each reduction process or join process based on the content, and the minimum working relation determining mechanism is configured to -1,2
... n, n is the working relation corresponding to the last process] σ) When determining the field configuration tube, if the process in step 7 is a reduction process, only the field of the relation that is the source of the reduction is used. The reference counter control mechanism checks whether the condition in question exists in the target query conditions, and if so, decrements the content of the corresponding reference counter by the number of times the field appears. At the same time, the condition is excluded from the target query conditions, and the contents of the reference counter are changed. After that, the contents of the reference counter group are read to determine the field configuration of the working relation for the reduction process, and the above is performed. If the first process is a join process, check whether a condition that uses only the fields of multiple relations to be jittered exists in the target query condition, and if it exists, check the corresponding reference counter. The reference counter control mechanism is requested to reduce the content of the field by the number of occurrences of the field, and the condition is excluded from the target query conditions, and after the content of the reference counter is changed, the reference counter group is The present invention is characterized in that it is configured to read the contents and determine the field structure of the work relation for the relevant di-in process. The present invention will be explained below with reference to the drawings.

Figure 1 is a diagram showing an overview of the relational database system, Figure 2 is a diagram showing the flow of processing in the logical data subsystem, Figure 3 is a diagram explaining processing in the scheduler, and Figure 4 is a diagram showing the flow of processing in the logical data subsystem. A diagram showing an example of a mechanism for determining the field configuration of a minimum work relay, FIG. 5 is a diagram showing an example of processing in the interpreter, FIG. 6 is a diagram showing an example of an inquiry, and FIG. 7 is an example of an inquiry. FIG. 8 is a diagram showing an example of the processing order, and FIG. 8 is a diagram showing an example of the state transition of the reference counter.

In FIG. 1, 1 is a relational database management system, 21d') a storage database,
3 represents a logical data subsystem, and 4 represents a logical storage subsystem. Relational database management system 1.

When an inquiry is input, the relational database 2 is accessed, one inquiry result is created, and this is transferred to the user. The relational database management system consists of a logical data subsystem 3 and a logical storage subsystem 4. The logical data subsystem 3 provides query analysis, optimization, execution, etc., and the logical storage subsystem 4 provides data storage, exclusive control, recovery, etc. The relational database 2 stores multiple relations (tables).

FIG. 2 shows the flow of processing in the logical data subsystem. As shown in Figure 2.

Logical data subsystem 3 performs syntactic analysis, semantic analysis,
Queries input to the logical data subsystem 3, which handles processing such as the scheduler and interrupter, are
Written in a non-procedural language.

Figure 6 shows an example of an interrogative sentence written in a non-procedural language. The question in Figure 6 is:

Field als affie "ms" 4e al
Let l be a ration A, field bllb*-bs
-b4t- with relay B and field e1m
ellm ea* e4 and range C, r:
Field a1 * JIS e bl l bl #C that satisfies the conditions shown below using WHERE
I am requesting that you create a 1e e4k Motsureshiron. The syntax analysis unit checks the syntax of the input query statement, the scheduler performs optimization and generates execution-continuation statements, and the interceptor executes execution procedure statements. It is something. An example of a procedural sentence corresponding to the inquiry sentence written in the non-procedural language of FIG. 6 has a structure as shown in FIG. Figure 7 is.

■Reduce the relay, yA, and convert the sono result to a
Sort by l and store the sort result in working relay TA.■ Reduce relay silon B and store the result in b.
Sort by l and use the sorting result as a working relay TBk.
Store it.

■ Enter working relations TA and TB under the conditions a, =:b, and convert the result to b! Store the note results in the working Relay Shiron TABk■ Reduce the Relay Shiron 0 and save the Sono result to C
3, and store the sorting results in the working relay TC.■ Create the working relations TAB and TO, and log in under the condition of =C2, and store the results in the working relay TABOK.

This means that.

FIG. 4 is a diagram showing an example of a mechanism for determining the field configuration of the minimum work relay.

In FIG. 4, 5 is a minimum working relay length determining mechanism, 6 is a reference counter control mechanism, 7 is a reference counter group, and 8 is a reference counter control mechanism.
indicate reference counters, respectively. One inquiry condition and processing order are entered into the minimum work relay determination mechanism 5 manually. This condition is #! WHERE in Figure 6
The processing order is specified by the following statement, and the processing order is as shown in FIG. Reference counter control mechanism 6JIIr reference force counter group 7tV. The reference counter group 7 has a plurality of reference counters 8t- corresponding to each of the fields cited in the inquiry, and each reference counter 8 has an initial value set therein. For example, in the case of the query shown in FIG. 6, field a appears twice in the sentence following GET, so the initial value of the reference counter 8 corresponding to field a is set to "2", and field a, appears once in the statement following GET, so the initial value of the reference counter 8 corresponding to field a is set to 1".

The same applies hereafter. When determining the minimum field configuration of the working relation TA that reduces the relation At and stores the result, the condition that only relates to the original relation AK is a, = 5, so the minimum working relation determining mechanism 5 is , field a, reference color 71 f>
Refer to "l" from the contents Counter controller 11
! Request 6. When the minimum work relation determination mechanism 5 finishes executing this request, it sends a counter reference request to the reference counter control mechanism 6. Upon receiving the counter reference request, the reference counter control mechanism 6 returns the contents of the -' reference counter group 7. At this time, since the content of the reference counter corresponding to field a* is zero, the working relation TA This is included in the optimization section of Figure 1, which determines that field 1 and a, t are most likely. The minimum field configuration of the working ridsion will be discussed in more detail below.

FIG. 5 shows an example of processing in the interpreter. This example starts with the β-th process that executes the process shown in FIG. The interpreter performs reduction or join according to the execution procedure statement created by the scheduler, creates a work relation for storing the reduction result or join result according to the scheduler's decision, and stores the processing result in this.

For example, the working relation for storing the results of ttIIJ Ration A is field) "a.

Since it has been determined by the scheduler to have a2 and a2, the interpreter creates a working relay TA with such a configuration and writes the result of reducing the relation person in ``chi,''.

As mentioned earlier, the least efficient method of not minimizing the field structure of the inquiry field TA, -TB, TO, and TAB shown in Figure 6 is to replace all fields of the original relation with the working field. It is included in the field of the image.

That is, the configuration is as follows.

TA(as e aIs aIs a41 al)T
B (bl#'h*ba 6 ba)TO(
C1e 'ff1e Cme' number)TAB
(”* # ”me ”so ”4* ”II bwe
bwe baa b4) By using the reference counter 7, the simple but inefficient method described above can be improved to a more efficient method using the minimum field configuration. Hereinafter, how to obtain a working relation having a minimum field configuration will be explained with reference to FIG. FIG. 8 shows the transition state of the reference counter when performing the process shown in FIG. 7, and in FIG. 8, the * mark indicates the reference counter changed in the immediately previous step.

Step (2) Regarding the condition Ps (see FIG. 6) in which only the field of relation A is used in the condition, the reference counter 8 corresponding to each field is decremented by the number of times it appears. The resulting state of the reference counter group 7 is as shown in FIG. 8(b) (condition P1 is excluded from the subsequent processing). Among the fields of relation A, those whose reference counter 8 is zero indicate that they are unnecessary as a field configuration of the working relation of reduction resultant 1 working relation T
This shows that it is good to have the field configuration of A as shown below.

TA (ate lL,) Step ■ Condition P that uses only the field of relation B in the condition (Jll Jle P2. ps, P4)
2, the same process as step (2) is performed (condition P3 is excluded from subsequent processing). The state of the reference counter group 7 obtained as a result is shown in Article 8 (c).

The following fields are used as the working relation TB:'''
IIIM, it can be determined that tp is sufficient.

:1ModuTB (bs, be, be) Step ■ Conditions Jl, P3 that use only the fields of the two working relations TA and TB that are joined in the conditions (Jl, Jl, ps, P4) Regarding K, the same process as in step (2) is performed (condition J 1e P s is excluded from the subsequent processing target). The resulting state of the reference counter group 7 is shown in FIG. It can be determined whether the working relation TAB should have the following field configuration.

TAB (a 1 @ & @I b to b dew) Step ■ Perform the same process as step 1 for condition P4 K, which uses only the field of relation C in condition 1 * pi (condition P4 is (excluded from the scope). The state of the reference counter group 7 obtained as a result is shown in FIG.
shown. It can be determined that the working relation TC should have the following field configuration.

TC(ele (so an) (μ step) Two working relations TA in the remaining conditions
Concerning the condition Jm that uses only the fields B and TO, perform the same process as in step (2) (this completes checking all conditions). The status of the reference counter group 7 obtained as a result is shown in Figure 8 ( ). The field structure of the working relation (which matches the final relation of the query result) is as follows.

TABC(ILse ale tlae tls+e
s* aJ As is clear from the above description, according to the present invention.

II. Using reference counters, the field configuration of working relations used in query processing in a relational database system can be determined in a much simpler way than k, and optimization efficiency can be improved.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the processing in the IJ database system scheduler, Fig. 4 is a diagram showing an embodiment of the mechanism for determining the entire field configuration of the minimum working relation, and Fig. 5 is a diagram explaining the processing in the IJ database system scheduler. 6 is a diagram showing an example of an inquiry, FIG. 7 is a diagram showing an example of an inquiry processing order, and FIG. 8 is a diagram showing an example of the state transition of a reference counter. It is. 1...Relational database management system,
2... Relation database, 3... Logical data subsystem, 4... Logical storage subsystem, 5... Minimum work relation determination mechanism, 6...
Reference counter control mechanism, 7... Reference counter group. 8...Reference counter. Patent Applicant Fujitsu Ltd. Representative Patent Attorney Kyotani 4 Parts 1 (¥1 Figure 2 Figure 3 Figure 4 (¥) Figure 5 (¥) Figure 26 Figure

Claims (1)

[Claims] A process sequence including a reduction process or a join process is added according to the inquiry information sent from the user, and the result of the reduction process or join process in the process of executing the process sequence is stored in a work relation. In a relational database system. A reference counter control mechanism having a plurality of reference counters in which the number of occurrences of the field in the query is set as a mutual initial value, with a one-to-one correspondence with the field appearing in the query, and query conditions and processing. requesting the reference counter control mechanism to change the contents of the reference counter based on the series, and storing the results of each reduction process or diversion process based on the contents of the reference counter group consisting of the plurality of reference counters; A minimum work/relationship determination mechanism is provided for determining a field configuration of a work relation, and the minimum work relationship determination mechanism is provided. When determining the field configuration of the relation using the action corresponding to the I-th process (i=], 2...n, where n is the last process), if that process is a reduction process, , check whether there is a condition in the target query condition that uses only the field of the reduction source. If it exists, it requests the reference counter control mechanism to reduce the contents of the corresponding reference counter by the number of times the field appears, excludes the condition from the target query conditions, and changes the contents of the reference counter. After that, the content of the reference counter group is read and the field configuration of the working relation for the relevant reduction process is determined. If the first process is a four-in process, check whether or not there are multiple relays in the query condition that uses only the field of the condition force I target, If it exists, request the above-mentioned reference counter control mechanism to reduce the corresponding reference counter by gt - the number of times the field appears, exclude it from the query conditions that are subject to the current condition, and change the contents of the reference counter. 1. A method for determining a minimum work relation, characterized in that the method is configured to read the contents of a reference counter group after a join process has been performed to determine a field configuration of a work relation for the join process.