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       Writing Data to HDFS |
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               <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/creating-external-tables-examples.html">Creating External Tables - Examples</a>
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                   <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-define-an-external-table-with-single-row-error-isolation.html">Define an External Table with Single Row Error Isolation</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-create-an-error-table-and-declare-a-reject-limit.html">Capture Row Formatting Errors and Declare a Reject Limit </a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-identifying-invalid-csv-files-in-error-table-data.html">Identifying Invalid CSV Files in Error Table Data</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-moving-data-between-tables.html">Moving Data between Tables</a></li>
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               <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-register_files.html">Registering Files into HAWQ Internal Tables</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-loading-data-with-hawqload.html">Loading Data with hawq load</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-loading-data-with-copy.html">Loading Data with COPY</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-running-copy-in-single-row-error-isolation-mode.html">Running COPY in Single Row Error Isolation Mode</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-optimizing-data-load-and-query-performance.html">Optimizing Data Load and Query Performance</a></li>
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                   <li class="has_submenu"><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-defining-a-file-based-writable-external-table.html">Defining a File-Based Writable External Table</a>
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                       <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-example-hawq-file-server-gpfdist.html">Example - HAWQ file server (gpfdist)</a></li>
                     </ul>
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                   <li class="has_submenu"><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-defining-a-command-based-writable-external-web-table.html">Defining a Command-Based Writable External Web Table</a>
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                       <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-disabling-execute-for-web-or-writable-external-tables.html">Disabling EXECUTE for Web or Writable External Tables</a></li>
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                   <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-unloading-data-using-a-writable-external-table.html">Unloading Data Using a Writable External Table</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-unloading-data-using-copy.html">Unloading Data Using COPY</a></li>
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               <li class="has_submenu"><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-transforming-xml-data.html">Transforming XML Data</a>
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                   <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-determine-the-transformation-schema.html">Determine the Transformation Schema</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-write-a-transform.html">Write a Transform</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-write-the-gpfdist-configuration.html">Write the gpfdist Configuration</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-load-the-data.html">Load the Data</a></li>
                   <li class="has_submenu"><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-transfer-and-store-the-data.html">Transfer and Store the Data</a>
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                       <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-transforming-with-gpload.html">Transforming with GPLOAD</a></li>
                       <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-transforming-with-insert-into-select-from.html">Transforming with INSERT INTO SELECT FROM</a></li>
                       <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-configuration-file-format.html">Configuration File Format</a></li>
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                       <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-example-1-dblp-database-publications-in-demo-directory.html">Command-based Web External Tables</a></li>
                       <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-example-irs-mef-xml-files-in-demo-directory.html">Example using IRS MeF XML Files (In demo Directory)</a></li>
                       <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-example-witsml-files-in-demo-directory.html">Example using WITSML™ Files (In demo Directory)</a></li>
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                   <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-representing-null-values.html">Representing NULL Values</a></li>
                   <li class="has_submenu"><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-escaping.html">Escaping</a>
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                       <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-escaping-in-csv-formatted-files.html">Escaping in CSV Formatted Files</a></li>
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                   <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/load/g-character-encoding.html">Character Encoding</a></li>
                 </ul>
               </li>
             </ul>
           </li>
           <li><a href="/docs/userguide/2.3.0.0-incubating/datamgmt/HAWQInputFormatforMapReduce.html">HAWQ InputFormat for MapReduce</a></li>
         </ul>
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       <li class="has_submenu"><a href="/docs/userguide/2.3.0.0-incubating/pxf/HawqExtensionFrameworkPXF.html">Using PXF with Unmanaged Data</a>
             <ul>
               <li><a href="/docs/userguide/2.3.0.0-incubating/pxf/InstallPXFPlugins.html">Installing PXF Plugins</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/pxf/ConfigurePXF.html">Configuring PXF</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/pxf/HDFSFileDataPXF.html">Accessing HDFS File Data</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/pxf/HivePXF.html">Accessing Hive Data</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/pxf/HBasePXF.html">Accessing HBase Data</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/pxf/JsonPXF.html">Accessing JSON Data</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/pxf/JdbcPXF.html">Accessing External SQL Databases</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/pxf/HDFSWritablePXF.html">Writing Data to HDFS</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/pxf/ReadWritePXF.html">Using Profiles to Read and Write Data</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/pxf/PXFExternalTableandAPIReference.html">PXF External Tables and API</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/pxf/TroubleshootingPXF.html">Troubleshooting PXF</a></li>
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       <li class="has_submenu"><a href="/docs/userguide/2.3.0.0-incubating/query/query.html">Querying Data</a>
         <ul>
           <li><a href="/docs/userguide/2.3.0.0-incubating/query/HAWQQueryProcessing.html">About HAWQ Query Processing</a></li>
           <li class="has_submenu"><a href="/docs/userguide/2.3.0.0-incubating/query/gporca/query-gporca-optimizer.html">About GPORCA</a>
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               <li><a href="/docs/userguide/2.3.0.0-incubating/query/gporca/query-gporca-overview.html">Overview of GPORCA</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/query/gporca/query-gporca-features.html">GPORCA Features and Enhancements</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/query/gporca/query-gporca-enable.html">Enabling GPORCA</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/query/gporca/query-gporca-notes.html">Considerations when Using GPORCA</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/query/gporca/query-gporca-fallback.html">Determining The Query Optimizer In Use</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/query/gporca/query-gporca-changed.html">Changed Behavior with GPORCA</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/query/gporca/query-gporca-limitations.html">GPORCA Limitations</a></li>
             </ul>
           </li>
           <li><a href="/docs/userguide/2.3.0.0-incubating/query/defining-queries.html">Defining Queries</a></li>
           <li><a href="/docs/userguide/2.3.0.0-incubating/query/functions-operators.html">Using Functions and Operators</a></li>
           <li><a href="/docs/userguide/2.3.0.0-incubating/query/query-performance.html">Query Performance</a></li>
           <li><a href="/docs/userguide/2.3.0.0-incubating/query/query-profiling.html">Query Profiling</a></li>
         </ul>
       </li>
       <li class="has_submenu"><a href="/docs/userguide/2.3.0.0-incubating/bestpractices/HAWQBestPracticesOverview.html">Best Practices</a>
         <ul>
           <li><a href="/docs/userguide/2.3.0.0-incubating/bestpractices/config_hawq_bestpractices.html">Configuring HAWQ</a></li>
           <li><a href="/docs/userguide/2.3.0.0-incubating/bestpractices/operating_hawq_bestpractices.html">Operating HAWQ</a></li>
           <li><a href="/docs/userguide/2.3.0.0-incubating/bestpractices/secure_bestpractices.html">Securing HAWQ</a></li>
           <li><a href="/docs/userguide/2.3.0.0-incubating/bestpractices/managing_resources_bestpractices.html">Managing Resources</a></li>
           <li><a href="/docs/userguide/2.3.0.0-incubating/bestpractices/managing_data_bestpractices.html">Managing Data</a></li>
           <li><a href="/docs/userguide/2.3.0.0-incubating/bestpractices/querying_data_bestpractices.html">Querying Data</a></li>
         </ul>
       </li>
       <li class="has_submenu"><a href="/docs/userguide/2.3.0.0-incubating/troubleshooting/Troubleshooting.html">Troubleshooting</a>
         <ul>
           <li><a href="/docs/userguide/2.3.0.0-incubating/troubleshooting/Troubleshooting.html#topic_dwd_rnx_15">Query Performance Issues</a></li>
           <li><a href="/docs/userguide/2.3.0.0-incubating/troubleshooting/Troubleshooting.html#topic_vm5_znx_15">Rejection of Query Resource Requests</a></li>
           <li><a href="/docs/userguide/2.3.0.0-incubating/troubleshooting/Troubleshooting.html#topic_qq4_rkl_wv">Queries Cancelled Due to High VMEM Usage</a></li>
           <li><a href="/docs/userguide/2.3.0.0-incubating/troubleshooting/Troubleshooting.html#topic_hlj_zxx_15">Segments Do Not Appear in gp_segment_configuration</a></li>
           <li><a href="/docs/userguide/2.3.0.0-incubating/troubleshooting/Troubleshooting.html#topic_mdz_q2y_15">Handling Segment Resource Fragmentation</a></li>
         </ul>
       </li>
       <li class="has_submenu"><a href="/docs/userguide/2.3.0.0-incubating/reference/hawq-reference.html">HAWQ Reference</a>
         <ul>
           <li class="has_submenu"><a href="/docs/userguide/2.3.0.0-incubating/reference/SQLCommandReference.html">SQL Commands</a>
             <ul>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/ABORT.html">ABORT</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/ALTER-AGGREGATE.html">ALTER AGGREGATE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/ALTER-CONVERSION.html">ALTER CONVERSION</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/ALTER-DATABASE.html">ALTER DATABASE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/ALTER-FUNCTION.html">ALTER FUNCTION</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/ALTER-OPERATOR.html">ALTER OPERATOR</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/ALTER-OPERATOR-CLASS.html">ALTER OPERATOR CLASS</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/ALTER-RESOURCE-QUEUE.html">ALTER RESOURCE QUEUE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/ALTER-ROLE.html">ALTER ROLE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/ALTER-SEQUENCE.html">ALTER SEQUENCE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/ALTER-TABLE.html">ALTER TABLE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/ALTER-TABLESPACE.html">ALTER TABLESPACE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/ALTER-TYPE.html">ALTER TYPE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/ALTER-USER.html">ALTER USER</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/ANALYZE.html">ANALYZE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/BEGIN.html">BEGIN</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CHECKPOINT.html">CHECKPOINT</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CLOSE.html">CLOSE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/COMMIT.html">COMMIT</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/COPY.html">COPY</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-AGGREGATE.html">CREATE AGGREGATE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-CAST.html">CREATE CAST</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-CONVERSION.html">CREATE CONVERSION</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-DATABASE.html">CREATE DATABASE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-EXTERNAL-TABLE.html">CREATE EXTERNAL TABLE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-FUNCTION.html">CREATE FUNCTION</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-GROUP.html">CREATE GROUP</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-LANGUAGE.html">CREATE LANGUAGE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-OPERATOR.html">CREATE OPERATOR</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-OPERATOR-CLASS.html">CREATE OPERATOR CLASS</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-RESOURCE-QUEUE.html">CREATE RESOURCE QUEUE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-ROLE.html">CREATE ROLE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-SCHEMA.html">CREATE SCHEMA</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-SEQUENCE.html">CREATE SEQUENCE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-TABLE.html">CREATE TABLE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-TABLE-AS.html">CREATE TABLE AS</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-TABLESPACE.html">CREATE TABLESPACE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-TYPE.html">CREATE TYPE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-USER.html">CREATE USER</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-VIEW.html">CREATE VIEW</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DEALLOCATE.html">DEALLOCATE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DECLARE.html">DECLARE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-AGGREGATE.html">DROP AGGREGATE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-CAST.html">DROP CAST</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-CONVERSION.html">DROP CONVERSION</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-DATABASE.html">DROP DATABASE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-EXTERNAL-TABLE.html">DROP EXTERNAL TABLE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-FILESPACE.html">DROP FILESPACE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-FUNCTION.html">DROP FUNCTION</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-GROUP.html">DROP GROUP</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-LANGUAGE.html">DROP LANGUAGE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-OPERATOR.html">DROP OPERATOR</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-OPERATOR-CLASS.html">DROP OPERATOR CLASS</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-OWNED.html">DROP OWNED</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-RESOURCE-QUEUE.html">DROP RESOURCE QUEUE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-ROLE.html">DROP ROLE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-SCHEMA.html">DROP SCHEMA</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-SEQUENCE.html">DROP SEQUENCE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-TABLE.html">DROP TABLE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-TABLESPACE.html">DROP TABLESPACE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-TYPE.html">DROP TYPE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-USER.html">DROP USER</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/DROP-VIEW.html">DROP VIEW</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/END.html">END</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/EXECUTE.html">EXECUTE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/EXPLAIN.html">EXPLAIN</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/FETCH.html">FETCH</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/GRANT.html">GRANT</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/INSERT.html">INSERT</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/PREPARE.html">PREPARE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/REASSIGN-OWNED.html">REASSIGN OWNED</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/RELEASE-SAVEPOINT.html">RELEASE SAVEPOINT</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/RESET.html">RESET</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/REVOKE.html">REVOKE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/ROLLBACK.html">ROLLBACK</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/ROLLBACK-TO-SAVEPOINT.html">ROLLBACK TO SAVEPOINT</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/SAVEPOINT.html">SAVEPOINT</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/SELECT.html">SELECT</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/SELECT-INTO.html">SELECT INTO</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/SET.html">SET</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/SET-ROLE.html">SET ROLE</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/SET-SESSION-AUTHORIZATION.html">SET SESSION AUTHORIZATION</a></li>
               <li><a href="/docs/userguide/2.3.0.0-incubating/reference/sql/SHOW.html">SHOW</a></li>
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                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#enable_seqscan">enable_seqscan</a></li>
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                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#enable_tidscan">enable_tidscan</a></li>
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                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#topic_imj_zhf_gw">gp_autostats_on_change_threshhold</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_backup_directIO">gp_backup_directIO</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_backup_directIO_read_chunk_mb">gp_backup_directIO_read_chunk_mb</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_cached_segworkers_threshold">gp_cached_segworkers_threshold</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_command_count">gp_command_count</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_connections_per_thread">gp_connections_per_thread</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_debug_linger">gp_debug_linger</a></li>
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                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_enable_agg_distinct_pruning">gp_enable_agg_distinct_pruning</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_enable_direct_dispatch">gp_enable_direct_dispatch</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_enable_fallback_plan">gp_enable_fallback_plan</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_enable_fast_sri">gp_enable_fast_sri</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_enable_groupext_distinct_gather">gp_enable_groupext_distinct_gather</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_enable_groupext_distinct_pruning">gp_enable_groupext_distinct_pruning</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_enable_multiphase_agg">gp_enable_multiphase_agg</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_enable_predicate_propagation">gp_enable_predicate_propagation</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_enable_preunique">gp_enable_preunique</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_enable_sequential_window_plans">gp_enable_sequential_window_plans</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_enable_sort_distinct">gp_enable_sort_distinct</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_enable_sort_limit">gp_enable_sort_limit</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_external_enable_exec">gp_external_enable_exec</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_external_grant_privileges">gp_external_grant_privileges</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_external_max_segs">gp_external_max_segs</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_filerep_tcp_keepalives_count">gp_filerep_tcp_keepalives_count</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_filerep_tcp_keepalives_idle">gp_filerep_tcp_keepalives_idle</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_filerep_tcp_keepalives_interval">gp_filerep_tcp_keepalives_interval</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_hashjoin_tuples_per_bucket">gp_hashjoin_tuples_per_bucket</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_idf_deduplicate">gp_idf_deduplicate</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_interconnect_cache_future_packets">gp_interconnect_cache_future_packets</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_interconnect_default_rtt">gp_interconnect_default_rtt</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_interconnect_fc_method">gp_interconnect_fc_method</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_interconnect_hash_multiplier">gp_interconnect_hash_multiplier</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_interconnect_min_retries_before_timeout">gp_interconnect_min_retries_before_timeout</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_interconnect_min_rto">gp_interconnect_min_rto</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_interconnect_queue_depth">gp_interconnect_queue_depth</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_interconnect_setup_timeout">gp_interconnect_setup_timeout</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_interconnect_snd_queue_depth">gp_interconnect_snd_queue_depth</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_interconnect_timer_checking_period">gp_interconnect_timer_checking_period</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_interconnect_timer_period">gp_interconnect_timer_period</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_interconnect_type">gp_interconnect_type</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_log_format">gp_log_format</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_max_csv_line_length">gp_max_csv_line_length</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_max_databases">gp_max_databases</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_max_filespaces">gp_max_filespaces</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_max_packet_size">gp_max_packet_size</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_max_plan_size">gp_max_plan_size</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_max_tablespaces">gp_max_tablespaces</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_motion_cost_per_row">gp_motion_cost_per_row</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_reject_percent_threshold">gp_reject_percent_threshold</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_reraise_signal">gp_reraise_signal</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_role">gp_role</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_safefswritesize">gp_safefswritesize</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_segment_connect_timeout">gp_segment_connect_timeout</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_segments_for_planner">gp_segments_for_planner</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_session_id">gp_session_id</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_set_proc_affinity">gp_set_proc_affinity</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_set_read_only">gp_set_read_only</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_statistics_pullup_from_child_partition">gp_statistics_pullup_from_child_partition</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_statistics_use_fkeys">gp_statistics_use_fkeys</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_vmem_idle_resource_timeout">gp_vmem_idle_resource_timeout</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_vmem_protect_segworker_cache_limit">gp_vmem_protect_segworker_cache_limit</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_workfile_checksumming">gp_workfile_checksumming</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_workfile_compress_algorithm">gp_workfile_compress_algorithm</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_workfile_limit_files_per_query">gp_workfile_limit_files_per_query</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_workfile_limit_per_query">gp_workfile_limit_per_query</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#gp_workfile_limit_per_segment">gp_workfile_limit_per_segment</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_acl_type">hawq_acl_type</a></li>
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                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_global_rm_type">hawq_global_rm_type</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_master_address_host">hawq_master_address_host</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_master_address_port">hawq_master_address_port</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_master_directory">hawq_master_directory</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_master_temp_directory">hawq_master_temp_directory</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_re_memory_overcommit_max">hawq_re_memory_overcommit_max</a></li>
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                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_rm_force_alterqueue_cancel_queued_request">hawq_rm_force_alterqueue_cancel_queued_request</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_rm_master_port">hawq_rm_master_port</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_rm_memory_limit_perseg">hawq_rm_memory_limit_perseg</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_rm_min_resource_perseg">hawq_rm_min_resource_perseg</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_rm_nresqueue_limit">hawq_rm_nresqueue_limit</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_rm_nslice_perseg_limit">hawq_rm_nslice_perseg_limit</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_rm_nvcore_limit_perseg">hawq_rm_nvcore_limit_perseg</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_rm_nvseg_perquery_limit">hawq_rm_nvseg_perquery_limit</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_rm_nvseg_perquery_perseg_limit">hawq_rm_nvseg_perquery_perseg_limit</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_rm_nvseg_variance_amon_seg_limit">hawq_rm_nvseg_variance_amon_seg_limit</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_rm_rejectrequest_nseg_limit">hawq_rm_rejectrequest_nseg_limit</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_rm_resource_idle_timeout">hawq_rm_resource_idle_timeout</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_rm_return_percent_on_overcommit">hawq_rm_return_percent_on_overcommit</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_rm_segment_heartbeat_interval">hawq_rm_segment_heartbeat_interval</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_rm_segment_port">hawq_rm_segment_port</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_rm_stmt_nvseg">hawq_rm_stmt_nvseg</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_rm_stmt_vseg_memory">hawq_rm_stmt_vseg_memory</a></li>
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                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_rps_check_local_interval">hawq_rps_check_local_interval</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#hawq_segment_address_port">hawq_segment_address_port</a></li>
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                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#lc_ctype">lc_ctype</a></li>
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                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#lc_monetary">lc_monetary</a></li>
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                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#log_autostats">log_autostats</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#log_connections">log_connections</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#log_disconnections">log_disconnections</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#log_dispatch_stats">log_dispatch_stats</a></li>
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                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#log_error_verbosity">log_error_verbosity</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#log_executor_stats">log_executor_stats</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#log_hostname">log_hostname</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#log_min_duration_statement">log_min_duration_statement</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#log_min_error_statement">log_min_error_statement</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#log_min_messages">log_min_messages</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#log_parser_stats">log_parser_stats</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#log_planner_stats">log_planner_stats</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#log_rotation_age">log_rotation_age</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#log_rotation_size">log_rotation_size</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#log_statement">log_statement</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#log_statement_stats">log_statement_stats</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#log_timezone">log_timezone</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#log_truncate_on_rotation">log_truncate_on_rotation</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#max_appendonly_tables">max_appendonly_tables</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#max_connections">max_connections</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#max_files_per_process">max_files_per_process</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#max_fsm_pages">max_fsm_pages</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#max_fsm_relations">max_fsm_relations</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#max_function_args">max_function_args</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#max_identifier_length">max_identifier_length</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#max_index_keys">max_index_keys</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#max_locks_per_transaction">max_locks_per_transaction</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#max_prepared_transactions">max_prepared_transactions</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#max_stack_depth">max_stack_depth</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#optimizer">optimizer</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#optimizer_analyze_root_partition">optimizer_analyze_root_partition</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#optimizer_minidump">optimizer_minidump</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#optimizer_parts_to_force_sort_on_insert">optimizer_parts_to_force_sort_on_insert</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#optimizer_prefer_scalar_dqa_multistage_agg">optimizer_prefer_scalar_dqa_multistage_agg</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#password_encryption">password_encryption</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#pgstat_track_activity_query_size">pgstat_track_activity_query_size</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#pljava_classpath">pljava_classpath</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#pljava_statement_cache_size">pljava_statement_cache_size</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#pljava_release_lingering_savepoints">pljava_release_lingering_savepoints</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#pljava_vmoptions">pljava_vmoptions</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#port">port</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#pxf_enable_filter_pushdown">pxf_enable_filter_pushdown</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#pxf_enable_stat_collection">pxf_enable_stat_collection</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#pxf_remote_service_login">pxf_remote_service_login</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#pxf_remote_service_secret">pxf_remote_service_secret</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#pxf_service_address">pxf_service_address</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#pxf_service_port">pxf_service_port</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#pxf_stat_max_fragments">pxf_stat_max_fragments</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#random_page_cost">random_page_cost</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#regex_flavor">regex_flavor</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#runaway_detector_activation_percent">runaway_detector_activation_percent</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#search_path">search_path</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#seg_max_connections">seg_max_connections</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#seq_page_cost">seq_page_cost</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#server_encoding">server_encoding</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#server_ticket_renew_interval">server_ticket_renew_interval</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#server_version">server_version</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#server_version_num">server_version_num</a></li>
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                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#ssl">ssl</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#ssl_ciphers">ssl_ciphers</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#standard_conforming_strings">standard_conforming_strings</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#statement_timeout">statement_timeout</a></li>
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                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#tcp_keepalives_count">tcp_keepalives_count</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#tcp_keepalives_idle">tcp_keepalives_idle</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#tcp_keepalives_interval">tcp_keepalives_interval</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#temp_buffers">temp_buffers</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#TimeZone">TimeZone</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#timezone_abbreviations">timezone_abbreviations</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#track_activities">track_activities</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#track_counts">track_counts</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#transaction_isolation">transaction_isolation</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#transaction_read_only">transaction_read_only</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#transform_null_equals">transform_null_equals</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#unix_socket_directory">unix_socket_directory</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#unix_socket_group">unix_socket_group</a></li>
                   <li><a href="/docs/userguide/2.3.0.0-incubating/reference/guc/parameter_definitions.html#unix_socket_permissions">unix_socket_permissions</a></li>
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           <h1 class="title-container" >
     Writing Data to HDFS
   </h1>


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             <div class="quick-links"><ul>
 <li><a href="#pxfwrite_prereq">Prerequisites</a></li>
 <li><a href="#hdfsplugin_writeextdata">Writing to PXF External Tables</a></li>
 <li><a href="#profile_hdfstextsimple">Custom Options</a></li>
 <li>
 <a href="#profile_hdfstextsimple">HdfsTextSimple Profile</a><ul><li><a href="#profile_hdfstextsimple_writing">Example: Writing Data Using the HdfsTextSimple Profile</a></li></ul>
 </li>
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 <a href="#profile_hdfsseqwritable_using">SequenceWritable Profile</a><ul><li><a href="#profile_hdfsseqwritable_writing">Example: Writing Data Using the SequenceWritable Profile</a></li></ul>
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 <a href="#recordkeyinkey-valuefileformats">Reading the Record Key</a><ul><li><a href="#example1">Example: Using Record Keys</a></li></ul>
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 <p>The PXF HDFS plug-in supports writable external tables using the <code>HdfsTextSimple</code> and <code>SequenceWritable</code> profiles.  You might create a writable table to export data from a HAWQ internal table to binary or text HDFS files.</p>

 <p>Use the <code>HdfsTextSimple</code> profile when writing text data. Use the <code>SequenceWritable</code> profile when dealing with binary data.</p>

 <p>This section describes how to use these PXF profiles to create writable external tables.</p>

 <p><strong>Note</strong>: Tables that you create with writable profiles can only be used for INSERT operations.  If you want to query inserted data, you must define a separate external readable table that references the new HDFS file using the equivalent readable profile.</p>

 <h2 id="prerequisites"><a id="pxfwrite_prereq"></a>Prerequisites</h2>

 <p>Before working with HDFS file data using HAWQ and PXF, ensure that:</p>

 <ul>
 <li>  The HDFS plug-in is installed on all cluster nodes. See <a href="/docs/userguide/2.3.0.0-incubating/pxf/InstallPXFPlugins.html">Installing PXF Plug-ins</a> for PXF plug-in installation information.</li>
 <li>  All HDFS users have read permissions to HDFS services.</li>
 <li>  HDFS write permissions are provided to a restricted set of users.</li>
 </ul>

 <h2 id="writing-to-pxf-external-tables"><a id="hdfsplugin_writeextdata"></a>Writing to PXF External Tables</h2>

 <p>The PXF HDFS plug-in supports two writable profiles: <code>HdfsTextSimple</code> and <code>SequenceWritable</code>.</p>

 <p>Use the following syntax to create a HAWQ external writable table representing HDFS data: </p>
 <pre class="highlight sql"><code><span class="k">CREATE</span> <span class="n">WRITABLE</span> <span class="k">EXTERNAL</span> <span class="k">TABLE</span> <span class="o">&lt;</span><span class="k">table_name</span><span class="o">&gt;</span>
     <span class="p">(</span> <span class="o">&lt;</span><span class="k">column_name</span><span class="o">&gt;</span> <span class="o">&lt;</span><span class="n">data_type</span><span class="o">&gt;</span> <span class="p">[,</span> <span class="p">...]</span> <span class="o">|</span> <span class="k">LIKE</span> <span class="o">&lt;</span><span class="n">other_table</span><span class="o">&gt;</span> <span class="p">)</span>
 <span class="k">LOCATION</span> <span class="p">(</span><span class="s1">'pxf://&lt;host&gt;[:&lt;port&gt;]/&lt;path-to-hdfs-file&gt;
     ?PROFILE=HdfsTextSimple|SequenceWritable[&amp;&lt;custom-option&gt;=&lt;value&gt;[...]]'</span><span class="p">)</span>
 <span class="n">FORMAT</span> <span class="s1">'[TEXT|CSV|CUSTOM]'</span> <span class="p">(</span><span class="o">&lt;</span><span class="n">formatting</span><span class="o">-</span><span class="n">properties</span><span class="o">&gt;</span><span class="p">);</span>
 </code></pre>

 <p>HDFS-plug-in-specific keywords and values used in the <a href="/docs/userguide/2.3.0.0-incubating/reference/sql/CREATE-EXTERNAL-TABLE.html">CREATE EXTERNAL TABLE</a> call are described in the table below.</p>

 <table><thead>
 <tr>
 <th>Keyword</th>
 <th>Value</th>
 </tr>
 </thead><tbody>
 <tr>
 <td>&lt;host&gt;</td>
 <td>The PXF host. While &lt;host&gt; may identify any PXF agent node, use the HDFS NameNode as it is guaranteed to be available in a running HDFS cluster. If HDFS High Availability is enabled, &lt;host&gt; must identify the HDFS NameService.</td>
 </tr>
 <tr>
 <td>&lt;port&gt;</td>
 <td>The PXF port. If &lt;port&gt; is omitted, PXF assumes &lt;host&gt; identifies a High Availability HDFS Nameservice and connects to the port number designated by the <code>pxf_service_port</code> server configuration parameter value. Default is 51200.</td>
 </tr>
 <tr>
 <td>&lt;path-to-hdfs-file&gt;</td>
 <td>The path to the file in the HDFS data store.</td>
 </tr>
 <tr>
 <td>PROFILE</td>
 <td>The <code>PROFILE</code> keyword must specify one of the values <code>HdfsTextSimple</code> or <code>SequenceWritable</code>.</td>
 </tr>
 <tr>
 <td>&lt;custom-option&gt;</td>
 <td>&lt;custom-option&gt; is profile-specific. These options are discussed in the next topic.</td>
 </tr>
 <tr>
 <td>FORMAT &lsquo;TEXT&rsquo;</td>
 <td>Use &rsquo;<code>TEXT</code>&rsquo; <code>FORMAT</code> with the <code>HdfsTextSimple</code> profile to create a plain-text-delimited file at the location specified by &lt;path-to-hdfs-file&gt;. The <code>HdfsTextSimple</code> &rsquo;<code>TEXT</code>&rsquo; <code>FORMAT</code> supports only the built-in <code>(delimiter=&lt;delim&gt;)</code> &lt;formatting-property&gt;.</td>
 </tr>
 <tr>
 <td>FORMAT &#39;CSV&rsquo;</td>
 <td>Use &rsquo;<code>CSV</code>&rsquo; <code>FORMAT</code> with the <code>HdfsTextSimple</code> profile to create a comma-separated-value file at the location specified by &lt;path-to-hdfs-file&gt;.</td>
 </tr>
 <tr>
 <td>FORMAT &#39;CUSTOM&rsquo;</td>
 <td>Use the <code>&#39;CUSTOM&#39;</code> <code>FORMAT</code> with the <code>SequenceWritable</code> profile. The <code>SequenceWritable</code> &rsquo;<code>CUSTOM</code>&rsquo; <code>FORMAT</code> supports only the built-in <code>(formatter=&#39;pxfwritable_export)</code> (write) and <code>(formatter=&#39;pxfwritable_import)</code> (read) &lt;formatting-properties&gt;.</td>
 </tr>
 </tbody></table>

 <p><strong>Note</strong>: When creating PXF external tables, you cannot use the <code>HEADER</code> option in your <code>FORMAT</code> specification.</p>

 <h2 id="custom-options"><a id="profile_hdfstextsimple"></a>Custom Options</h2>

 <p>The <code>HdfsTextSimple</code> and <code>SequenceWritable</code> profiles support the following custom options:</p>

 <table><thead>
 <tr>
 <th>Option</th>
 <th>Value Description</th>
 <th>Profile</th>
 </tr>
 </thead><tbody>
 <tr>
 <td>COMPRESSION_CODEC</td>
 <td>The compression codec Java class name. If this option is not provided, no data compression is performed. Supported compression codecs include: <code>org.apache.hadoop.io.compress.DefaultCodec</code> and <code>org.apache.hadoop.io.compress.BZip2Codec</code></td>
 <td>HdfsTextSimple, SequenceWritable</td>
 </tr>
 <tr>
 <td>COMPRESSION_CODEC</td>
 <td><code>org.apache.hadoop.io.compress.GzipCodec</code></td>
 <td>HdfsTextSimple</td>
 </tr>
 <tr>
 <td>COMPRESSION_TYPE</td>
 <td>The compression type to employ; supported values are <code>RECORD</code> (the default) or <code>BLOCK</code>.</td>
 <td>HdfsTextSimple, SequenceWritable</td>
 </tr>
 <tr>
 <td>DATA-SCHEMA</td>
 <td>The name of the writer serialization/deserialization class. The jar file in which this class resides must be in the PXF classpath. This option is required for the <code>SequenceWritable</code> profile and has no default value.</td>
 <td>SequenceWritable</td>
 </tr>
 <tr>
 <td>THREAD-SAFE</td>
 <td>Boolean value determining if a table query can run in multi-threaded mode. The default value is <code>TRUE</code>. Set this option to <code>FALSE</code> to handle all requests in a single thread for operations that are not thread-safe (for example, compression).</td>
 <td>HdfsTextSimple, SequenceWritable</td>
 </tr>
 </tbody></table>

 <h2 id="hdfstextsimple-profile"><a id="profile_hdfstextsimple"></a>HdfsTextSimple Profile</h2>

 <p>Use the <code>HdfsTextSimple</code> profile when writing delimited data to a plain text file where each line is a single record.</p>

 <p>Writable tables created using the <code>HdfsTextSimple</code> profile can optionally use record or block compression. The following compression codecs are supported:</p>

 <ul>
 <li>org.apache.hadoop.io.compress.DefaultCodec</li>
 <li>org.apache.hadoop.io.compress.GzipCodec</li>
 <li>org.apache.hadoop.io.compress.BZip2Codec</li>
 </ul>

 <p>The <code>HdfsTextSimple</code> profile supports the following &lt;formatting-properties&gt;:</p>

 <table><thead>
 <tr>
 <th>Keyword</th>
 <th>Value</th>
 </tr>
 </thead><tbody>
 <tr>
 <td>delimiter</td>
 <td>The delimiter character to use when writing the file. Default value is a comma <code>,</code>.</td>
 </tr>
 </tbody></table>

 <h3 id="example:-writing-data-using-the-hdfstextsimple-profile"><a id="profile_hdfstextsimple_writing"></a>Example: Writing Data Using the HdfsTextSimple Profile</h3>

 <p>This example uses the data schema introduced in <a href="/docs/userguide/2.3.0.0-incubating/pxf/HDFSFileDataPXF.html#profile_hdfstextsimple_query">Example: Using the HdfsTextSimple Profile</a>:</p>

 <table><thead>
 <tr>
 <th>Field Name</th>
 <th>Data Type</th>
 </tr>
 </thead><tbody>
 <tr>
 <td>location</td>
 <td>text</td>
 </tr>
 <tr>
 <td>month</td>
 <td>text</td>
 </tr>
 <tr>
 <td>number_of_orders</td>
 <td>int</td>
 </tr>
 <tr>
 <td>total_sales</td>
 <td>float8</td>
 </tr>
 </tbody></table>

 <p>This example also uses the HAWQ table <code>pxf_hdfs_textsimple</code> created in that exercise and expects it to exist.</p>

 <p>Perform the following operations to use the PXF <code>HdfsTextSimple</code> profile to create a HAWQ writable external table with the same data schema as defined above. You will also create a separate external readable table to read the associated HDFS file.</p>

 <ol>
 <li><p>Create a writable HAWQ external table with the data schema described above. Write to the HDFS file <code>/data/pxf_examples/pxfwritable_hdfs_textsimple1</code>. Create the table specifying a comma <code>,</code> as the delimiter:</p>
 <pre class="highlight sql"><code><span class="n">gpadmin</span><span class="o">=#</span> <span class="k">CREATE</span> <span class="n">WRITABLE</span> <span class="k">EXTERNAL</span> <span class="k">TABLE</span> <span class="n">pxf_hdfs_writabletbl_1</span><span class="p">(</span><span class="k">location</span> <span class="n">text</span><span class="p">,</span> <span class="k">month</span> <span class="n">text</span><span class="p">,</span> <span class="n">num_orders</span> <span class="n">int</span><span class="p">,</span> <span class="n">total_sales</span> <span class="n">float8</span><span class="p">)</span>
             <span class="k">LOCATION</span> <span class="p">(</span><span class="s1">'pxf://namenode:51200/data/pxf_examples/pxfwritable_hdfs_textsimple1?PROFILE=HdfsTextSimple'</span><span class="p">)</span>
           <span class="n">FORMAT</span> <span class="s1">'TEXT'</span> <span class="p">(</span><span class="k">delimiter</span><span class="o">=</span><span class="n">E</span><span class="s1">','</span><span class="p">);</span>
 </code></pre>

 <p>The <code>FORMAT</code> subclause <code>delimiter</code> value is specified as the single ascii comma character <code>,</code>. <code>E</code> escapes the character.</p></li>
 <li><p>Write a few records to the <code>pxfwritable_hdfs_textsimple1</code> HDFS file by invoking the SQL <code>INSERT</code> command on <code>pxf_hdfs_writabletbl_1</code>:</p>
 <pre class="highlight sql"><code><span class="n">gpadmin</span><span class="o">=#</span> <span class="k">INSERT</span> <span class="k">INTO</span> <span class="n">pxf_hdfs_writabletbl_1</span> <span class="k">VALUES</span> <span class="p">(</span> <span class="s1">'Frankfurt'</span><span class="p">,</span> <span class="s1">'Mar'</span><span class="p">,</span> <span class="mi">777</span><span class="p">,</span> <span class="mi">3956</span><span class="p">.</span><span class="mi">98</span> <span class="p">);</span>
 <span class="n">gpadmin</span><span class="o">=#</span> <span class="k">INSERT</span> <span class="k">INTO</span> <span class="n">pxf_hdfs_writabletbl_1</span> <span class="k">VALUES</span> <span class="p">(</span> <span class="s1">'Cleveland'</span><span class="p">,</span> <span class="s1">'Oct'</span><span class="p">,</span> <span class="mi">3812</span><span class="p">,</span> <span class="mi">96645</span><span class="p">.</span><span class="mi">37</span> <span class="p">);</span>
 </code></pre></li>
 <li><p>Insert the contents of the <code>pxf_hdfs_textsimple</code> table created in <a href="/docs/userguide/2.3.0.0-incubating/pxf/HDFSFileDataPXF.html#profile_hdfstextsimple_query">Example: Using the HdfsTextSimple Profile</a> into <code>pxf_hdfs_writabletbl_1</code>:</p>
 <pre class="highlight sql"><code><span class="n">gpadmin</span><span class="o">=#</span> <span class="k">INSERT</span> <span class="k">INTO</span> <span class="n">pxf_hdfs_writabletbl_1</span> <span class="k">SELECT</span> <span class="o">*</span> <span class="k">FROM</span> <span class="n">pxf_hdfs_textsimple</span><span class="p">;</span>
 </code></pre></li>
 <li><p>View the file contents in HDFS:</p>
 <pre class="highlight shell"><code><span class="gp">$ </span>hdfs dfs -cat /data/pxf_examples/pxfwritable_hdfs_textsimple1/<span class="k">*</span>
 Frankfurt,Mar,777,3956.98
 Cleveland,Oct,3812,96645.37
 Prague,Jan,101,4875.33
 Rome,Mar,87,1557.39
 Bangalore,May,317,8936.99
 Beijing,Jul,411,11600.67
 </code></pre>

 <p>Because you specified comma <code>,</code> as the delimiter, this character is the field separator used in each record of the HDFS file.</p></li>
 <li><p>Querying an external writable table is not supported in HAWQ. To query data from the newly-created HDFS file, create a readable external HAWQ table referencing the HDFS file:</p>
 <pre class="highlight sql"><code><span class="n">gpadmin</span><span class="o">=#</span> <span class="k">CREATE</span> <span class="k">EXTERNAL</span> <span class="k">TABLE</span> <span class="n">pxf_hdfs_textsimple_r1</span><span class="p">(</span><span class="k">location</span> <span class="n">text</span><span class="p">,</span> <span class="k">month</span> <span class="n">text</span><span class="p">,</span> <span class="n">num_orders</span> <span class="n">int</span><span class="p">,</span> <span class="n">total_sales</span> <span class="n">float8</span><span class="p">)</span>
             <span class="k">LOCATION</span> <span class="p">(</span><span class="s1">'pxf://namenode:51200/data/pxf_examples/pxfwritable_hdfs_textsimple1?PROFILE=HdfsTextSimple'</span><span class="p">)</span>
             <span class="n">FORMAT</span> <span class="s1">'CSV'</span><span class="p">;</span>
 </code></pre>

 <p>Specify the <code>&#39;CSV&#39;</code> <code>FORMAT</code> for the readable table, because you created the writable table with a comma <code>,</code> as the delimiter character.</p></li>
 <li><p>Query the readable external table <code>pxf_hdfs_textsimple_r1</code>:</p>
 <pre class="highlight sql"><code><span class="n">gpadmin</span><span class="o">=#</span> <span class="k">SELECT</span> <span class="o">*</span> <span class="k">FROM</span> <span class="n">pxf_hdfs_textsimple_r1</span><span class="p">;</span>
 </code></pre>
 <pre class="highlight plaintext"><code> location  | month | num_orders | total_sales
 -----------+-------+------------+-------------
   Frankfurt | Mar   |        777 |     3956.98
   Cleveland | Oct   |       3812 |    96645.37
   Prague    | Jan   |        101 |     4875.33
   Rome      | Mar   |         87 |     1557.39
   Bangalore | May   |        317 |     8936.99
   Beijing   | Jul   |        411 |    11600.67
 (6 rows)
 </code></pre>

 <p>The table includes the records you individually inserted, as well as the full contents of the <code>pxf_hdfs_textsimple</code> table.</p></li>
 <li><p>Create a second HAWQ external writable table, this time using Gzip compression and employing a colon <code>:</code> as the delimiter:</p>
 <pre class="highlight sql"><code><span class="n">gpadmin</span><span class="o">=#</span> <span class="k">CREATE</span> <span class="n">WRITABLE</span> <span class="k">EXTERNAL</span> <span class="k">TABLE</span> <span class="n">pxf_hdfs_writabletbl_2</span> <span class="p">(</span><span class="k">location</span> <span class="n">text</span><span class="p">,</span> <span class="k">month</span> <span class="n">text</span><span class="p">,</span> <span class="n">num_orders</span> <span class="n">int</span><span class="p">,</span> <span class="n">total_sales</span> <span class="n">float8</span><span class="p">)</span>
             <span class="k">LOCATION</span> <span class="p">(</span><span class="s1">'pxf://namenode:51200/data/pxf_examples/pxfwritable_hdfs_textsimple2?PROFILE=HdfsTextSimple&amp;COMPRESSION_CODEC=org.apache.hadoop.io.compress.GzipCodec'</span><span class="p">)</span>
           <span class="n">FORMAT</span> <span class="s1">'TEXT'</span> <span class="p">(</span><span class="k">delimiter</span><span class="o">=</span><span class="n">E</span><span class="s1">':'</span><span class="p">);</span>
 </code></pre></li>
 <li><p>Write a few records to the <code>pxfwritable_hdfs_textsimple2</code> HDFS file by inserting into the <code>pxf_hdfs_writabletbl_2</code> table:</p>
 <pre class="highlight sql"><code><span class="n">gpadmin</span><span class="o">=#</span> <span class="k">INSERT</span> <span class="k">INTO</span> <span class="n">pxf_hdfs_writabletbl_2</span> <span class="k">VALUES</span> <span class="p">(</span> <span class="s1">'Frankfurt'</span><span class="p">,</span> <span class="s1">'Mar'</span><span class="p">,</span> <span class="mi">777</span><span class="p">,</span> <span class="mi">3956</span><span class="p">.</span><span class="mi">98</span> <span class="p">);</span>
 <span class="n">gpadmin</span><span class="o">=#</span> <span class="k">INSERT</span> <span class="k">INTO</span> <span class="n">pxf_hdfs_writabletbl_2</span> <span class="k">VALUES</span> <span class="p">(</span> <span class="s1">'Cleveland'</span><span class="p">,</span> <span class="s1">'Oct'</span><span class="p">,</span> <span class="mi">3812</span><span class="p">,</span> <span class="mi">96645</span><span class="p">.</span><span class="mi">37</span> <span class="p">);</span>
 </code></pre></li>
 <li><p>View the file contents in HDFS; use the <code>-text</code> option to <code>hdfs dfs</code> to view the compressed data as text:</p>
 <pre class="highlight shell"><code><span class="gp">$ </span>hdfs dfs -text /data/pxf_examples/pxfwritable_hdfs_textsimple2/<span class="k">*</span>
 Frankfurt:Mar:777:3956.98
 Cleveland:Oct:3812:96645.3
 </code></pre>

 <p>Notice that the colon <code>:</code> is the field separator in the HDFS file.</p>

 <p>As described in Step 5 above, to query data from the newly-created HDFS file named <code>pxfwritable_hdfs_textsimple2</code>, you can create a readable external HAWQ table referencing this HDFS file.</p></li>
 </ol>

 <h2 id="sequencewritable-profile"><a id="profile_hdfsseqwritable_using"></a>SequenceWritable Profile</h2>

 <p>Use the HDFS plug-in <code>SequenceWritable</code> profile when writing SequenceFile format files. Files of this type consist of binary key/value pairs. Sequence files are a common data transfer format between MapReduce jobs. </p>

 <p>SequenceFile format files can optionally use record or block compression. The following compression codecs are supported:</p>

 <ul>
 <li>org.apache.hadoop.io.compress.DefaultCodec</li>
 <li>org.apache.hadoop.io.compress.BZip2Codec</li>
 </ul>

 <p>When using the <code>SequenceWritable</code> profile to write a SequenceFile format file, you must provide the name of the Java class to use for serializing/deserializing the data. This class must provide read and write methods for the fields in the schema associated with the data.</p>

 <h3 id="example:-writing-data-using-the-sequencewritable-profile"><a id="profile_hdfsseqwritable_writing"></a>Example: Writing Data Using the SequenceWritable Profile</h3>

 <p>In this example, you will create a Java class named <code>PxfExample_CustomWritable</code> that will serialize/deserialize the fields in the sample schema used in previous examples. You will then use this class to access a writable external table created with the <code>SequenceWritable</code> profile. </p>

 <p>Perform the following steps to create the Java class and writable table.</p>

 <ol>
 <li><p>Prepare to create the sample Java class:</p>
 <pre class="highlight shell"><code><span class="gp">$ </span>mkdir -p pxfex/com/hawq/example/pxf/hdfs/writable/dataschema
 <span class="gp">$ </span><span class="nb">cd </span>pxfex/com/hawq/example/pxf/hdfs/writable/dataschema
 <span class="gp">$ </span>vi PxfExample_CustomWritable.java
 </code></pre></li>
 <li><p>Copy and paste the following text into the <code>PxfExample_CustomWritable.java</code> file:</p>
 <pre class="highlight java"><code><span class="kn">package</span> <span class="n">com</span><span class="o">.</span><span class="na">hawq</span><span class="o">.</span><span class="na">example</span><span class="o">.</span><span class="na">pxf</span><span class="o">.</span><span class="na">hdfs</span><span class="o">.</span><span class="na">writable</span><span class="o">.</span><span class="na">dataschema</span><span class="o">;</span>

 <span class="kn">import</span> <span class="nn">org.apache.hadoop.io.*</span><span class="o">;</span>
 <span class="kn">import</span> <span class="nn">java.io.DataInput</span><span class="o">;</span>
 <span class="kn">import</span> <span class="nn">java.io.DataOutput</span><span class="o">;</span>
 <span class="kn">import</span> <span class="nn">java.io.IOException</span><span class="o">;</span>
 <span class="kn">import</span> <span class="nn">java.lang.reflect.Field</span><span class="o">;</span>

 <span class="cm">/**
 * PxfExample_CustomWritable class - used to serialize and deserialize data with
 * text, int, and float data types
 */</span>
 <span class="kd">public</span> <span class="kd">class</span> <span class="nc">PxfExample_CustomWritable</span> <span class="kd">implements</span> <span class="n">Writable</span> <span class="o">{</span>

 <span class="kd">public</span> <span class="n">String</span> <span class="n">st1</span><span class="o">,</span> <span class="n">st2</span><span class="o">;</span>
 <span class="kd">public</span> <span class="kt">int</span> <span class="n">int1</span><span class="o">;</span>
 <span class="kd">public</span> <span class="kt">float</span> <span class="n">ft</span><span class="o">;</span>

 <span class="kd">public</span> <span class="nf">PxfExample_CustomWritable</span><span class="o">()</span> <span class="o">{</span>
     <span class="n">st1</span> <span class="o">=</span> <span class="k">new</span> <span class="n">String</span><span class="o">(</span><span class="s">""</span><span class="o">);</span>
     <span class="n">st2</span> <span class="o">=</span> <span class="k">new</span> <span class="n">String</span><span class="o">(</span><span class="s">""</span><span class="o">);</span>
     <span class="n">int1</span> <span class="o">=</span> <span class="mi">0</span><span class="o">;</span>
     <span class="n">ft</span> <span class="o">=</span> <span class="mi">0</span><span class="o">.</span><span class="na">f</span><span class="o">;</span>
 <span class="o">}</span>

 <span class="kd">public</span> <span class="nf">PxfExample_CustomWritable</span><span class="o">(</span><span class="kt">int</span> <span class="n">i1</span><span class="o">,</span> <span class="kt">int</span> <span class="n">i2</span><span class="o">,</span> <span class="kt">int</span> <span class="n">i3</span><span class="o">)</span> <span class="o">{</span>

     <span class="n">st1</span> <span class="o">=</span> <span class="k">new</span> <span class="n">String</span><span class="o">(</span><span class="s">"short_string___"</span> <span class="o">+</span> <span class="n">i1</span><span class="o">);</span>
     <span class="n">st2</span> <span class="o">=</span> <span class="k">new</span> <span class="n">String</span><span class="o">(</span><span class="s">"short_string___"</span> <span class="o">+</span> <span class="n">i1</span><span class="o">);</span>
     <span class="n">int1</span> <span class="o">=</span> <span class="n">i2</span><span class="o">;</span>
     <span class="n">ft</span> <span class="o">=</span> <span class="n">i1</span> <span class="o">*</span> <span class="mi">10</span><span class="o">.</span><span class="na">f</span> <span class="o">*</span> <span class="mf">2.3f</span><span class="o">;</span>

 <span class="o">}</span>

 <span class="n">String</span> <span class="nf">GetSt1</span><span class="o">()</span> <span class="o">{</span>
     <span class="k">return</span> <span class="n">st1</span><span class="o">;</span>
 <span class="o">}</span>

 <span class="n">String</span> <span class="nf">GetSt2</span><span class="o">()</span> <span class="o">{</span>
     <span class="k">return</span> <span class="n">st2</span><span class="o">;</span>
 <span class="o">}</span>

 <span class="kt">int</span> <span class="nf">GetInt1</span><span class="o">()</span> <span class="o">{</span>
     <span class="k">return</span> <span class="n">int1</span><span class="o">;</span>
 <span class="o">}</span>

 <span class="kt">float</span> <span class="nf">GetFt</span><span class="o">()</span> <span class="o">{</span>
     <span class="k">return</span> <span class="n">ft</span><span class="o">;</span>
 <span class="o">}</span>

 <span class="nd">@Override</span>
 <span class="kd">public</span> <span class="kt">void</span> <span class="nf">write</span><span class="o">(</span><span class="n">DataOutput</span> <span class="n">out</span><span class="o">)</span> <span class="kd">throws</span> <span class="n">IOException</span> <span class="o">{</span>

     <span class="n">Text</span> <span class="n">txt</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Text</span><span class="o">();</span>
     <span class="n">txt</span><span class="o">.</span><span class="na">set</span><span class="o">(</span><span class="n">st1</span><span class="o">);</span>
     <span class="n">txt</span><span class="o">.</span><span class="na">write</span><span class="o">(</span><span class="n">out</span><span class="o">);</span>
     <span class="n">txt</span><span class="o">.</span><span class="na">set</span><span class="o">(</span><span class="n">st2</span><span class="o">);</span>
     <span class="n">txt</span><span class="o">.</span><span class="na">write</span><span class="o">(</span><span class="n">out</span><span class="o">);</span>

     <span class="n">IntWritable</span> <span class="n">intw</span> <span class="o">=</span> <span class="k">new</span> <span class="n">IntWritable</span><span class="o">();</span>
     <span class="n">intw</span><span class="o">.</span><span class="na">set</span><span class="o">(</span><span class="n">int1</span><span class="o">);</span>
     <span class="n">intw</span><span class="o">.</span><span class="na">write</span><span class="o">(</span><span class="n">out</span><span class="o">);</span>

     <span class="n">FloatWritable</span> <span class="n">fw</span> <span class="o">=</span> <span class="k">new</span> <span class="n">FloatWritable</span><span class="o">();</span>
     <span class="n">fw</span><span class="o">.</span><span class="na">set</span><span class="o">(</span><span class="n">ft</span><span class="o">);</span>
     <span class="n">fw</span><span class="o">.</span><span class="na">write</span><span class="o">(</span><span class="n">out</span><span class="o">);</span>
 <span class="o">}</span>

 <span class="nd">@Override</span>
 <span class="kd">public</span> <span class="kt">void</span> <span class="nf">readFields</span><span class="o">(</span><span class="n">DataInput</span> <span class="n">in</span><span class="o">)</span> <span class="kd">throws</span> <span class="n">IOException</span> <span class="o">{</span>

     <span class="n">Text</span> <span class="n">txt</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Text</span><span class="o">();</span>
     <span class="n">txt</span><span class="o">.</span><span class="na">readFields</span><span class="o">(</span><span class="n">in</span><span class="o">);</span>
     <span class="n">st1</span> <span class="o">=</span> <span class="n">txt</span><span class="o">.</span><span class="na">toString</span><span class="o">();</span>
     <span class="n">txt</span><span class="o">.</span><span class="na">readFields</span><span class="o">(</span><span class="n">in</span><span class="o">);</span>
     <span class="n">st2</span> <span class="o">=</span> <span class="n">txt</span><span class="o">.</span><span class="na">toString</span><span class="o">();</span>

     <span class="n">IntWritable</span> <span class="n">intw</span> <span class="o">=</span> <span class="k">new</span> <span class="n">IntWritable</span><span class="o">();</span>
     <span class="n">intw</span><span class="o">.</span><span class="na">readFields</span><span class="o">(</span><span class="n">in</span><span class="o">);</span>
     <span class="n">int1</span> <span class="o">=</span> <span class="n">intw</span><span class="o">.</span><span class="na">get</span><span class="o">();</span>

     <span class="n">FloatWritable</span> <span class="n">fw</span> <span class="o">=</span> <span class="k">new</span> <span class="n">FloatWritable</span><span class="o">();</span>
     <span class="n">fw</span><span class="o">.</span><span class="na">readFields</span><span class="o">(</span><span class="n">in</span><span class="o">);</span>
     <span class="n">ft</span> <span class="o">=</span> <span class="n">fw</span><span class="o">.</span><span class="na">get</span><span class="o">();</span>
 <span class="o">}</span>

 <span class="kd">public</span> <span class="kt">void</span> <span class="nf">printFieldTypes</span><span class="o">()</span> <span class="o">{</span>
     <span class="n">Class</span> <span class="n">myClass</span> <span class="o">=</span> <span class="k">this</span><span class="o">.</span><span class="na">getClass</span><span class="o">();</span>
     <span class="n">Field</span><span class="o">[]</span> <span class="n">fields</span> <span class="o">=</span> <span class="n">myClass</span><span class="o">.</span><span class="na">getDeclaredFields</span><span class="o">();</span>

     <span class="k">for</span> <span class="o">(</span><span class="kt">int</span> <span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="o">;</span> <span class="n">i</span> <span class="o">&lt;</span> <span class="n">fields</span><span class="o">.</span><span class="na">length</span><span class="o">;</span> <span class="n">i</span><span class="o">++)</span> <span class="o">{</span>
         <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">fields</span><span class="o">[</span><span class="n">i</span><span class="o">].</span><span class="na">getType</span><span class="o">().</span><span class="na">getName</span><span class="o">());</span>
     <span class="o">}</span>
 <span class="o">}</span>
 <span class="o">}</span>
 </code></pre></li>
 <li><p>Compile and create a Java class JAR file for <code>PxfExample_CustomWritable</code>:</p>
 <pre class="highlight shell"><code><span class="gp">$ </span>javac -classpath /usr/hdp/2.5.3.0-37/hadoop/hadoop-common.jar  PxfExample_CustomWritable.java
 <span class="gp">$ </span><span class="nb">cd</span> ../../../../../../../
 <span class="gp">$ </span>jar cf pxfex-customwritable.jar com
 <span class="gp">$ </span>cp pxfex-customwritable.jar /tmp/
 </code></pre>

 <p>(Your Hadoop library classpath may differ.)</p></li>
 <li><p>Include the new jar file in the PXF Agent classpath by updating the <code>pxf-public.classpath</code> file. If you use Ambari to manage your cluster, add the following line via the Ambari UI and restart the PXF Agent:</p>
 <pre class="highlight plaintext"><code>/tmp/pxfex-customwritable.jar
 </code></pre>

 <p>If you have a command-line-managed HAWQ cluster, perform the following steps on each node in your HAWQ cluster:</p>

 <ul>
 <li>Directly edit <code>/etc/pxf/conf/pxf-public.classpath</code> and add the line above.</li>
 <li><p>Restart the PXF Agent:</p>
 <pre class="highlight shell"><code><span class="gp">$ </span>sudo service pxf-service restart
 </code></pre></li>
 </ul></li>
 <li><p>Use the PXF <code>SequenceWritable</code> profile to create a writable HAWQ external table. Identify the serialization/deserialization Java class you created above in the <code>DATA-SCHEMA</code> &lt;custom-option&gt;. Use <code>BLOCK</code> mode compression with <code>BZip2</code> when creating the writable table.</p>
 <pre class="highlight sql"><code><span class="n">gpadmin</span><span class="o">=#</span> <span class="k">CREATE</span> <span class="n">WRITABLE</span> <span class="k">EXTERNAL</span> <span class="k">TABLE</span> <span class="n">pxf_tbl_seqwrit</span> <span class="p">(</span><span class="k">location</span> <span class="n">text</span><span class="p">,</span> <span class="k">month</span> <span class="n">text</span><span class="p">,</span> <span class="n">number_of_orders</span> <span class="n">integer</span><span class="p">,</span> <span class="n">total_sales</span> <span class="n">real</span><span class="p">)</span>
             <span class="k">LOCATION</span> <span class="p">(</span><span class="s1">'pxf://namenode:51200/data/pxf_examples/pxf_seqwrit_file?PROFILE=SequenceWritable&amp;DATA-SCHEMA=com.hawq.example.pxf.hdfs.writable.dataschema.PxfExample_CustomWritable&amp;COMPRESSION_TYPE=BLOCK&amp;COMPRESSION_CODEC=org.apache.hadoop.io.compress.BZip2Codec'</span><span class="p">)</span>
           <span class="n">FORMAT</span> <span class="s1">'CUSTOM'</span> <span class="p">(</span><span class="n">formatter</span><span class="o">=</span><span class="s1">'pxfwritable_export'</span><span class="p">);</span>
 </code></pre>

 <p>Notice that the <code>&#39;CUSTOM&#39;</code> <code>FORMAT</code> &lt;formatting-properties&gt; specify the built-in <code>pxfwritable_export</code> formatter.</p></li>
 <li><p>Insert some data into <code>pxf_tbl_seqwrit</code>:</p>
 <pre class="highlight sql"><code><span class="n">gpadmin</span><span class="o">=#</span> <span class="k">INSERT</span> <span class="k">INTO</span> <span class="n">pxf_tbl_seqwrit</span> <span class="k">VALUES</span> <span class="p">(</span> <span class="s1">'Frankfurt'</span><span class="p">,</span> <span class="s1">'Mar'</span><span class="p">,</span> <span class="mi">777</span><span class="p">,</span> <span class="mi">3956</span><span class="p">.</span><span class="mi">98</span> <span class="p">);</span>
 <span class="n">gpadmin</span><span class="o">=#</span> <span class="k">INSERT</span> <span class="k">INTO</span> <span class="n">pxf_tbl_seqwrit</span> <span class="k">VALUES</span> <span class="p">(</span> <span class="s1">'Cleveland'</span><span class="p">,</span> <span class="s1">'Oct'</span><span class="p">,</span> <span class="mi">3812</span><span class="p">,</span> <span class="mi">96645</span><span class="p">.</span><span class="mi">37</span> <span class="p">);</span>
 </code></pre></li>
 <li><p>Recall that querying an external writable table is not supported in HAWQ. To read the newly-created writable table, create a HAWQ readable external table referencing the writable table&rsquo;s HDFS file:</p>
 <pre class="highlight sql"><code><span class="n">gpadmin</span><span class="o">=#</span> <span class="k">CREATE</span> <span class="k">EXTERNAL</span> <span class="k">TABLE</span> <span class="n">read_pxf_tbl_seqwrit</span> <span class="p">(</span><span class="k">location</span> <span class="n">text</span><span class="p">,</span> <span class="k">month</span> <span class="n">text</span><span class="p">,</span> <span class="n">number_of_orders</span> <span class="n">integer</span><span class="p">,</span> <span class="n">total_sales</span> <span class="n">real</span><span class="p">)</span>
             <span class="k">LOCATION</span> <span class="p">(</span><span class="s1">'pxf://namenode:51200/data/pxf_examples/pxf_seqwrit_file?PROFILE=SequenceWritable&amp;DATA-SCHEMA=com.hawq.example.pxf.hdfs.writable.dataschema.PxfExample_CustomWritable'</span><span class="p">)</span>
           <span class="n">FORMAT</span> <span class="s1">'CUSTOM'</span> <span class="p">(</span><span class="n">formatter</span><span class="o">=</span><span class="s1">'pxfwritable_import'</span><span class="p">);</span>
 </code></pre>

 <p>The <code>DATA-SCHEMA</code> &lt;custom-option&gt; must be specified when reading an HDFS file via the <code>SequenceWritable</code> profile. Compression-related options need not be provided.</p></li>
 <li><p>Query the readable external table <code>read_pxf_tbl_seqwrit</code>:</p>
 <pre class="highlight sql"><code><span class="n">gpadmin</span><span class="o">=#</span> <span class="k">SELECT</span> <span class="o">*</span> <span class="k">FROM</span> <span class="n">read_pxf_tbl_seqwrit</span><span class="p">;</span>
 </code></pre>
 <pre class="highlight plaintext"><code> location  | month | number_of_orders | total_sales
 -----------+-------+------------------+-------------
  Frankfurt | Mar   |              777 |     3956.98
  Cleveland | Oct   |             3812 |     96645.4
 (2 rows)
 </code></pre></li>
 </ol>

 <h2 id="reading-the-record-key"><a id="recordkeyinkey-valuefileformats"></a>Reading the Record Key</h2>

 <p>When a HAWQ external table references a SequenceFile or another file format that store rows in a key-value format, you can access the key values in HAWQ queries by using the <code>recordkey</code> keyword as a field name.</p>

 <p>The field type of <code>recordkey</code> must correspond to the key type, much as the other fields must match the HDFS data. </p>

 <p><code>recordkey</code> can be any of the following Hadoop types:</p>

 <ul>
 <li>  BooleanWritable</li>
 <li>  ByteWritable</li>
 <li>  DoubleWritable</li>
 <li>  FloatWritable</li>
 <li>  IntWritable</li>
 <li>  LongWritable</li>
 <li>  Text</li>
 </ul>

 <h3 id="example:-using-record-keys"><a id="example1"></a>Example: Using Record Keys</h3>

 <p>Create an external readable table to access the record keys from the writable table <code>pxf_tbl_seqwrit</code> that you created in <a href="#profile_hdfsseqwritable_writing">Example: Writing Data Using the SequenceWritable Profile</a>.  The <code>recordkey</code> is of type <code>int8</code>.</p>
 <pre class="highlight sql"><code><span class="n">gpadmin</span><span class="o">=#</span> <span class="k">CREATE</span>  <span class="k">EXTERNAL</span> <span class="k">TABLE</span> <span class="n">read_pxf_tbl_seqwrit_RECKEY</span> <span class="p">(</span><span class="n">recordkey</span> <span class="n">int8</span><span class="p">,</span> <span class="k">location</span> <span class="n">text</span><span class="p">,</span> <span class="k">month</span> <span class="n">text</span><span class="p">,</span> <span class="n">number_of_orders</span> <span class="n">integer</span><span class="p">,</span> <span class="n">total_sales</span> <span class="n">real</span><span class="p">)</span>
                 <span class="k">LOCATION</span> <span class="p">(</span><span class="s1">'pxf://namenode:51200/data/pxf_examples/pxf_seqwrit_file?PROFILE=SequenceWritable&amp;DATA-SCHEMA=com.hawq.example.pxf.hdfs.writable.dataschema.PxfExample_CustomWritable'</span><span class="p">)</span>
           <span class="n">FORMAT</span> <span class="s1">'CUSTOM'</span> <span class="p">(</span><span class="n">formatter</span><span class="o">=</span><span class="s1">'pxfwritable_import'</span><span class="p">);</span>
 <span class="n">gpadmin</span><span class="o">=#</span> <span class="k">SELECT</span> <span class="o">*</span> <span class="k">FROM</span> <span class="n">read_pxf_tbl_seqwrit_RECKEY</span><span class="p">;</span>
 </code></pre>
 <pre class="highlight plaintext"><code> recordkey |  location   | month | number_of_orders | total_sales
 -----------+-------------+-------+------------------+-------------
          0 | Frankfurt   | Mar   |              777 |     3956.98
          0 | Cleveland   | Oct   |             3812 |     96645.4
 (2 rows)
 </code></pre>

 <p>The <code>recordkey</code> is <code>0</code> because you did not identify a record key when you inserted entries into the writable table.</p>


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