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Method and apparatus for predicate evaluation on compressed variable-length character strings

A predicate evaluation and string technology, which is applied in electrical digital data processing, instruments, calculations, etc., can solve the problems of not making good use of performance advantages, not supporting predicate evaluation, etc., and achieve the effect of enhancing usability and performance

Active Publication Date: 2018-11-27
IBM CORP
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Problems solved by technology

Clearly, this solution does not support predicate evaluation on compressed-encoded data with trailing whitespace-insensitive semantics, and thus does not take advantage of the performance benefits of direct predicate evaluation on compressed data

Method used

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  • Method and apparatus for predicate evaluation on compressed variable-length character strings
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  • Method and apparatus for predicate evaluation on compressed variable-length character strings

Examples

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no. 1 example

[0025] The following will refer to figure 2 A method of predicate evaluation on compressed variable-length character strings according to a first embodiment of the present invention is described. In this embodiment, the compressed variable-length character string is compressed using a compression encoding method that makes the sequence of the compressed encoded data consistent with the order under the tail space sensitive semantics, and is performed under the tail space insensitive semantics. The predicate evaluation described is illustrated as an example.

[0026] First, the basic idea of ​​this embodiment and the technical terms involved are briefly described.

[0027] Although as mentioned above, variable-length strings have different orderings under trailing whitespace-insensitive semantics and trailing whitespace-sensitive semantics, so it is difficult to find an appropriate compression encoding that preserves order for both semantics way, but actually most variable-le...

no. 2 example

[0076] In the method for predicate evaluation on compressed variable-length strings according to the first embodiment, for a variable-length string predicate, its false positive range and false negative range are respectively determined, and then according to the compressed variable Whether the length string falls within the compressed encoding's false-positive and false-negative ranges determines the result of the predicate evaluation. However, in fact, in many cases, it is not necessary to determine the false negative range and then determine whether the compressed variable-length character string falls within the false negative range of the compression encoding (ie steps S21, S24 and processing in S26). Hereinafter, an example will be described.

[0077] For example, according to the above description, it can be seen that the range of false positives is greater than or equal to the range of false negatives, so if the variable-length string of compressed encoding does not f...

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Abstract

A method and apparatus for predicate evaluation on compressed variable length strings is disclosed. The method includes: determining the upper and lower bounds of the false positive range of the predicate, which is the range in which false positive errors may occur as a result of the predicate evaluation; compressing and encoding the upper and lower bounds of the false positive range; performing a first comparison between the compressed variable-length string and the upper and lower bounds of the compression-encoded false positive range; and determining a result of the predicate evaluation based on at least a result of the first comparison. This method takes full advantage of the performance advantages of predicate evaluation on compressed data and improves query processing performance.

Description

technical field [0001] The present invention relates to the field of relational databases, and more particularly, to a method and device for performing predicate evaluation on compressed variable-length character strings. Background technique [0002] Recent research has shown that when performing query processing in relational databases, performing predicate evaluation directly on the compressed data stored in the database, rather than decompressing the compressed data and then performing predicate evaluation on the decompressed data can greatly improve query performance. Processing performance. In this field, a predicate that sequentially includes an argument, an operation relational operator or a logical operator, and a connection constant and whose argument does not include a function, expression, or clause is usually called a simple predicate, or a predicate for short. In database language, the operational relational or logical operators may include "=", ">", ">=...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G06F17/30G06F17/27
CPCG06F16/90344
Inventor 陈星刘少蓉
Owner IBM CORP
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