Skew-based costing for database queries
First Claim
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1. A method, comprising:
- considering skew to generate costs for query plans for executing a query in a database;
selecting a query plan to eliminate the skew so data load while executing the query is evenly distributed across multiple processors;
executing the query with the query plan with the multiple processors in a parallel processing system; and
traversing histogram intervals for partitioning columns of input data and identifying an interval with a most frequent value to consider the skew to generate the costs for the query plans.
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Abstract
One embodiment is a method that determines skew to predict costs for query plans for a database query. The method selects a query plan that accounts for the skew to evenly distribute processing load among multiple processors and then executes the query with the selected query plan.
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Citations
17 Claims
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1. A method, comprising:
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considering skew to generate costs for query plans for executing a query in a database; selecting a query plan to eliminate the skew so data load while executing the query is evenly distributed across multiple processors; executing the query with the query plan with the multiple processors in a parallel processing system; and traversing histogram intervals for partitioning columns of input data and identifying an interval with a most frequent value to consider the skew to generate the costs for the query plans. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A tangible computer readable storage medium having instructions for causing a computer to execute a method, comprising:
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estimating skew to predict costs for query plans for a query in a database, wherein estimating the skew comprises traversing histogram intervals for partitioning columns of input data and identifying an interval with a most frequent value; selecting a query plan that reduces the skew to uniformly distribute processing load among multiple processors; and executing the query with the query plan with the multiple processors in a parallel processing architecture. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. A computer system, comprising:
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a database; and a processor to; determine skew to predict costs for query plans for a query of the database, wherein determining the skew comprises traversing histogram intervals for partitioning columns of input data and identifying an interval with a most frequent value; select a query plan that accounts for the skew to evenly distribute processing load among multiple processors; and execute the query with the query plan with the multiple processors. - View Dependent Claims (15, 16, 17)
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Specification