Querying Data

• About Greenplum Query Processing
  This topic provides an overview of how Greenplum Database processes queries. Understanding this process can be useful when writing and tuning queries.
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  In Greenplum Database, the default GPORCA optimizer co-exists with the Postgres Planner.
• WITH Queries (Common Table Expressions)
  The WITH clause of the command provides a way to write subqueries for use in a larger SELECT query.
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  Description of user-defined and built-in functions and operators in Greenplum Database.
• Working with XML Data
  Greenplum Database supports the xml data type that stores XML data.
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  Greenplum Database dynamically eliminates irrelevant partitions in a table and optimally allocates memory for different operators in a query.
• Query Profiling
  Examine the query plans of poorly performing queries to identify possible performance tuning opportunities.