MIRRORING, IN MEMORY, DATA FROM DISK TO IMPROVE QUERY PERFORMANCE

摘要

Techniques are provided for maintaining data persistently in one format, but making that data available to a database server in more than one format. For example, one of the formats in which the data is made available for query processing is based on the on-disk format, while another of the formats in which the data is made available for query processing is independent of the on-disk format. Data that is in the format that is independent of the disk format may be maintained exclusively in volatile memory to reduce the overhead associated with keeping the data in sync with the on-disk format copies of the data.

主权项

1. A method comprising:
maintaining, on persistent storage, a database that is accessible to a database server; wherein the database includes persistent-format data, stored on the persistent storage, in a persistent format; converting the persistent-format data to a mirror format to produce mirror-format data; storing the mirror-format data within volatile memory; wherein the mirror format is different from the persistent format; wherein, within the volatile memory, the mirror-format data is accessible to the database server; wherein each data item in the mirror-format data is a copy of a corresponding data item in the persistent-format data; receiving, by the database server, a request to execute a database command that requires a required set of data items; and during execution of the database command:
the database server obtaining a first subset of data items, of the required set of data items, from the persistent-format data, andthe database server obtaining a second subset of data items, of the required set of data items, from the mirror-format data.