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TRACKING AND MAINTAINING EXPRESSION STATISTICS ACROSS DATABASE QUERIES
TRACKING AND MAINTAINING EXPRESSION STATISTICS ACROSS DATABASE QUERIES
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机译:跟踪和维护数据库查询中的表达统计信息
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摘要
Techniques are described for maintaining an expression statistics store that stores and updates metadata values for query expressions based on the occurrence of those query expressions within queries. In an embodiment, a database server instance receives a database query. In response, the database server instance identifies expressions within the database queries. The database server instance then determines whether an expression statistics store includes an entry for the particular expression. Responsive to determining that the expression statistics store includes an entry for the particular expression, the database server instance updates at least one metadata value in the entry based on the occurrence of the particular expression. Responsive to determining that the expression statistics store does not include an entry for the particular expression, the database server instance adds an entry for the particular expression.
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