Data access using decompression maps

摘要

Methods and apparatus, including computer program products, implementing and using techniques for decompressing data in a database system. A query is received, which pertains to a subset of data within a compressed set of data. One or more decompression strategies are evaluated using a cost model. The cost model includes an estimated filter factor. A low cost decompression strategy is selected based on the results of the evaluation of the one or more decompression strategies. One or more bytes representing the requested subset of data are located within the compressed set of data. Only a portion of the compressed data that corresponds to the subset of data is decompressed, using the selected decompression strategy, while leaving the remaining set of data in a compressed state.

主权项

1. A computer-implemented method for decompressing data in a database system, comprising:
receiving a query pertaining to a subset of data within a compressed set of data; evaluating one or more decompression strategies using a cost model, the cost model including an estimated filter factor; selecting a low cost decompression strategy based on the results of the evaluation of the one or more decompression strategies; locating one or more bytes representing the requested subset of data within the compressed set of data; and decompressing only a portion of the compressed data that corresponds to the subset of data, using the selected decompression strategy, while leaving the remaining set of data in a compressed state.