Value list compression (vlc) aware qualification
AssigneeTeradata US, Inc.
InventorsBhashyam Ramesh, Tirupathi Prabhu Bellapukonda, Philip Jason Benton, Donald Raymond Pederson
Life of this patent
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Abstract
A database includes a Value List Compression (VLC) predicate evaluator. A table identified in a query that is being processed is identified as having compressed data values. The predicate evaluator compares a query predicate of the query against actual decompressed values noted in a dictionary for the table and the predicate evaluator maintains a bitmap for selective ones of the actual values that satisfy the query predicate. The matched bitmap positions are processed against an index maintained in the table for the actual values to provide selective decompressed table entries as results for the query.
Claims20
A method, comprising:
- identifying a predicate for a query against a table that includes compressed data values;
- obtaining a dictionary having actual values for the compressed data values, each actual value including an index to corresponding entries within the table having that actual value;
- evaluating the predicate against the actual values in the dictionary and establishing a bitmap that identifies qualified and unqualified actual values;
- identifying select entries in the table by processing set bits of the bitmap and the corresponding indexes maintained with those actual values, and wherein predicate columns associated with the query that are unnecessary for query evaluation remain compressed;
- and
- returning the select entries as results for the predicate as decompressed values.
A method, comprising:
- receiving a predicate from a query;
- identifying at least one data compression in a table that the predicate is to be evaluated against;
- evaluating the predicate against at least one dictionary maintained for the at least one data compression of the table while entries in the table associated with the at least one data compression remain in a compressed format;
- and
- providing results to the predicate in response to the evaluating in a decompressed format.
A system, comprising:
- a data warehouse including:
- an access module processor configured to process a Value List Compression (VLC) aware predicate evaluator
- wherein the VLC aware predicate evaluator is configured to i) execute on a hardware processor of a network computing device, ii) evaluate a predicate of a query issued to the data warehouse against at least one dictionary for a compressed table that the predicate is to be processed against while the compressed table remains in a compressed format, and iii) return results from evaluation of the predicate in a decompressed format that is decompressed from the compressed table.
Dependencies are inferred from the claim text.