SELECTIVE DATABASE STATISTICS RECOLLECTION
First Claim
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1. A database management system comprising:
- a data dictionary implemented in a machine-accessible medium including rows of metadata, the metadata of each row to describe one or more of a column of a database table and a set of two or more columns forming an index stored in the database management system, wherein the metadata of at least a subset of the data dictionary rows includes;
a stale flag column implemented in a database that is to be set to true by a process that executes on a machine when the metadata of a row is determined to be out of date by the process.
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Abstract
The subject mater herein relates to database management and, more particularly, to selective database statistics recollection. Various embodiments provide one or more of system, methods, and software that identify database column and index states when statistics become stale to a point where query execution plans against respective columns and indexes fail to be efficient. These and other embodiments provide a way to update column and index statistics only when the statistics are determined to be stale. As a result, adverse database performance as a result of needless updating of database statistics is mitigated.
34 Citations
20 Claims
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1. A database management system comprising:
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a data dictionary implemented in a machine-accessible medium including rows of metadata, the metadata of each row to describe one or more of a column of a database table and a set of two or more columns forming an index stored in the database management system, wherein the metadata of at least a subset of the data dictionary rows includes; a stale flag column implemented in a database that is to be set to true by a process that executes on a machine when the metadata of a row is determined to be out of date by the process. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of maintaining statistics in a database management system, the method comprising:
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maintaining a modified data counter and a stale flag for each column and index within a database management system for which statistics are maintained; incrementing the modified data counter of a column or index for each insert, update, and delete that affects data in the respective column of the modified data counter; and setting the stale flag to true if the modified data counter reaches a threshold value. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. A computer readable medium, with instructions thereon to cause a suitably configured computer system to:
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write data into a temporary database table; collect statistics on the temporary table; compare the temporary table statistics with statistics of one or more columns or indexes in a target database the data is to be written to for storage to determine if the temporary table will cause the database statistics to become out of date; and write the temporary table data to the database and designate the statistics of one or more columns or indexes of the database as out of date if the statistics comparing indicates the database statistics are out of date with the addition of the temporary table data. - View Dependent Claims (17, 18, 19, 20)
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Specification