JPS60211541A - Data retireval circuit - Google Patents

Abstract

PURPOSE:To attain high speed data retrieval by using plural hash circuits and plural hash table memories. CONSTITUTION:The key value (a) is inputted to the hash circuits 1, 2 and the hash table memories 3, 4 at data retrieval. The hash circuit 1 applies hashing to the inputted key value (a) to generate an address (b) and reads the hash table memory 3. When the key section 3-1 of a read record and the inputted key value (a) are dissident, the hash table memory 3 resets a signal (i) and when they are coincident, the memory 3 sets the signal to output a data (e). The hash circuit 2 and the hash table memory 4 generate a data (f) and a signal (g) similarly. A selector 5 selects either of the data (e), (f) depending on the set/reset of the signal (i) to output a retrieval data (h). When either of the signals (i), (g) is set, the output (h) is a retrieved data and when the signals (i), (g) are both reset, it represents that the data of the key value (a) is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a data retrieval circuit using a hashing method used in small, high-speed computers and the like.

Conventional technology When searching a table consisting of multiple records with keys and data, a method has traditionally been used to reduce access time and speed up data searches by using a hashing method that performs functional operations that vary key values. ing.

Conventionally, in the data search circuit of this building, synonym processing (collision at the same address) that occurred as a result of hashing was handled by writing using a pointer, or by writing an entry to the next location in the hash table memory. This method was used, but it had the disadvantage that the processing was complicated and time-consuming.

OBJECTS OF THE INVENTION An object of the present invention is to provide a data retrieval circuit that solves the above-mentioned drawbacks by using a plurality of hash circuits and a plurality of hash table memories.

Structure of the Invention In order to achieve all of the above-mentioned objects, the present invention comprises a plurality of parallel-connected hash circuits having different hash functions, the same number of hash table memories connected to the valley hash circuits, and a selector. At the time of retrieval, read key values are input to the plurality of hash circuits and the plurality of hash table memories, respectively, and the address generated by the hash circuit of the first column is used to read the key value of the hash circuit connected to the hash circuit of the first column. If the key part of the record read from the hash table memory in one column matches the input key value, the data of the record is output, and if they do not match, the selector selects the hash circuit and hash table of the next column. A configuration is adopted in which a matching key value is selected from the memory, and data of the matching key value from the Haratsuyu table memory is output processed.

Example Next, embodiments of the present invention will be described with reference to the drawings.

In FIG. 1 showing an embodiment of the present invention as a block circuit diagram, the data retrieval circuit of the present invention has two hash circuits 1 and 2 having different hash functions, and is connected to these two hash circuits 1 and 2, respectively. and key part 3-1 of each record
．． It is composed of two hash table memories 3.4 such as 4-1 and data section 3-2.4-2, and a selector 5.

First, when writing data, an input key value a is hashed by the hash circuit 1 in the first column, becomes an address b, and an input record is written at position b in the hash table memory 3. If a record has already been written to the same address b in the hash table memory 3, the signal d is turned on.

At this time, the input key value a is hashed by the hash circuit 2 in the second column to address C, and the input record is written to address C in the hash table memory 4 in the second column. Hash circuit 1 in the first row and hash circuit 2 in the second row
Since the hash function of is a change, it is almost impossible for both to be synonyms.

Next, the key value a during data verification is input to the hash circuit 1.2 and the hash table memories 3 and 4.

Hatshu episode lol! r1 is the input key 1 [a ff1)
The address b'6 is generated by tucking, and the hash table memory 3 is read. If the key part 3-1 of the read record and the input key value a do not match, the hash table memory 3 turns off the signal i, and if they match, turns on the signal i and outputs the data part as e. .

Hack-Circuit 2. Badge-print memory 4 similarly generates data f and signal g.

The selector 5 selects data e, depending on the on/off value of the signal i.
Select one of f and output to h.

If either of the signals 1sg is on, the output is the retrieved data, and if both lyg are off, the key value a
This indicates that the data was not recorded.

In this way, the Shino2 5- It also has the effect of allowing high-speed data retrieval for systems.

□ Nao, the synonym for Hatshu Circuit 1 is Hatshu Circuit 2
Although it is not uncommon for the type to be coincidental with the synonym of , the number of such cases is extremely small. In this case, complicated processing similar to the conventional method will be performed, but the probability of this is extremely small) and is not enough to impair the speed of data retrieval.

Further, in this embodiment, two hash circuits and two hash table memories are provided, but the same explanation applies to three or more hash circuits.

Effects of the Invention As explained above, according to the present invention, a plurality of hash circuits and a plurality of hash table memories are provided, and synonyms generated in the hash circuit in the first column are processed in the hash circuit in the next column. This configuration has the effect of speeding up data searches.

[Brief explanation of the drawing]

FIG. 1 shows a block circuit diagram of an embodiment of the present invention. 6- 1.2...Hatush times L3, 4...Hatsh table memo 1c 3-1.4-1...Ki part, 3-2゜4- 2... Data section, 5...
・Selector, a...Input key value, b, c...
...Hashing address, del9g...
...Signal, e, f...Data from memory, h...Output. 7-

Claims (1)

[Claims] A plurality of series-connected hash circuits having different hash functions, a hash table memory of the same type a connected to each hash circuit, and a selector, and when retrieving data, the read key value is the same as that of the plural hash circuits. The key of the record read from the hash table memory of the first column connected to the hash circuit of the first column is input to each of the circuit and the plurality of hash table memories, and is generated by the hash circuit of the first column. If the part matches the input key value, the data of the record is output, and if it does not match, the selector selects the matching key value from the hash circuit and hash table memory of the next column, and A data retrieval circuit characterized in that it outputs and processes data from a hash table memory for key values.