query/gporca/query-gporca-optimizer.html.md.erb

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title: About GPORCA
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In HAWQ, you can use GPORCA or the legacy query optimizer.

**Note:** To use the GPORCA query optimizer, you must be running a version of HAWQ built with GPORCA, and GPORCA must be enabled in your HAWQ deployment.

These sections describe GPORCA functionality and usage:

-   **[Overview of GPORCA](../../query/gporca/query-gporca-overview.html)**

    GPORCA extends the planning and optimization capabilities of the HAWQ legacy optimizer.

-   **[GPORCA Features and Enhancements](../../query/gporca/query-gporca-features.html)**

    GPORCA includes enhancements for specific types of queries and operations:

-   **[Enabling GPORCA](../../query/gporca/query-gporca-enable.html)**

    Precompiled versions of HAWQ that include the GPORCA query optimizer enable it by default, no additional configuration is required. To use the GPORCA query optimizer in a HAWQ built from source, your build must include GPORCA. You must also enable specific HAWQ server configuration parameters at or after install time:

-   **[Considerations when Using GPORCA](../../query/gporca/query-gporca-notes.html)**

    To execute queries optimally with GPORCA, consider certain criteria for the query.

-   **[Determining The Query Optimizer In Use](../../query/gporca/query-gporca-fallback.html)**

    When GPORCA is enabled, you can determine if HAWQ is using GPORCA or is falling back to the legacy query optimizer.

-   **[Changed Behavior with GPORCA](../../query/gporca/query-gporca-changed.html)**

    When GPORCA is enabled, HAWQ's behavior changes. This topic describes these changes.

-   **[GPORCA Limitations](../../query/gporca/query-gporca-limitations.html)**

    There are limitations in HAWQ when GPORCA is enabled. GPORCA and the legacy query optimizer currently coexist in HAWQ because GPORCA does not support all HAWQ features.