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SQL query optimization hints

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## Introduction This API will help you optimize your sql queries for better performance.

## How to use Create an optimizer object specific to a single (database, schema) pair e.g. optimizer = get_optimizer(“presto”, schema)

Get optimization hints using optimize_query(query) e.g. presto_op.optimize_query(query)

Initial Optimization Checks
  • Using approximate algorithms (approx_distinct() instead of COUNT(DISTINCT …))

  • Selecting the columns the user wants explicitly, rather than using (SELECT *)

  • Filtering on partitioned columns

  • Try to extract nested subqueries using a WITH clause.

  • Suggest filtering on most effective columns, by parquet-file ordering

  • Eliminate filtering overhead for partitioned columns

Other Stuff
  • Replace UNION with UNION ALL if duplicates do not need to be removed

  • Aggregate a series of LIKE clauses into one regexp_like expression

  • Push down a complex join condition into a sub query

  • Specify GROUP BY targets with numbers for expressions

### Testing To run unit tests, run py.test (or py.test -s to see stdout) in the tests directory.

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