Github user dyozie commented on a diff in the pull request:
https://github.com/apache/incubator-hawq-docs/pull/46#discussion_r85845000
--- Diff: pxf/HDFSWritablePXF.html.md.erb ---
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+---
+title: Writing Data to HDFS
+---
+
+The PXF HDFS plug-in supports writable external tables using the
`HdfsTextSimple` and `SequenceWritable` profiles. You might create a writable
table to export data from a HAWQ internal table to HDFS.
+
+This section describes how to use these PXF profiles to create writable
external tables.
+
+**Note**: You cannot directly query data in a HAWQ writable table. After
creating the external writable table, you must create a HAWQ readable external
table accessing the HDFS file, then query that table. ??You can also create a
Hive table to access the HDFS file.??
+
+## <a id="pxfwrite_prereq"></a>Prerequisites
+
+Before working with HDFS file data using HAWQ and PXF, ensure that:
+
+- The HDFS plug-in is installed on all cluster nodes. See [Installing
PXF Plug-ins](InstallPXFPlugins.html) for PXF plug-in installation information.
+- All HDFS users have read permissions to HDFS services and that write
permissions have been restricted to specific users.
+
+## <a id="hdfsplugin_writeextdata"></a>Writing to PXF External Tables
+The PXF HDFS plug-in supports writable two profiles: `HdfsTextSimple` and
`SequenceWritable`.
+
+Use the following syntax to create a HAWQ external writable table
representing HDFS data:Â
+
+``` sql
+CREATE EXTERNAL WRITABLE TABLE <table_name>
+ ( <column_name> <data_type> [, ...] | LIKE <other_table> )
+LOCATION ('pxf://<host>[:<port>]/<path-to-hdfs-file>
+
?PROFILE=HdfsTextSimple|SequenceWritable[&<custom-option>=<value>[...]]')
+FORMAT '[TEXT|CSV|CUSTOM]' (<formatting-properties>);
+```
+
+HDFS-plug-in-specific keywords and values used in the [CREATE EXTERNAL
TABLE](../reference/sql/CREATE-EXTERNAL-TABLE.html) call are described in the
table below.
+
+| Keyword | Value |
+|-------|-------------------------------------|
+| \<host\>[:\<port\>] | The HDFS NameNode and port. |
+| \<path-to-hdfs-file\> | The path to the file in the HDFS data store. |
+| PROFILE | The `PROFILE` keyword must specify one of the values
`HdfsTextSimple` or `SequenceWritable`. |
+| \<custom-option\> | \<custom-option\> is profile-specific. These
options are discussed in the next topic.|
+| FORMAT 'TEXT' | Use '`TEXT`' `FORMAT` with the `HdfsTextSimple` profile
when \<path-to-hdfs-file\> will reference a plain text delimited file. The
`HdfsTextSimple` '`TEXT`' `FORMAT` supports only the built-in
`(delimiter=<delim>)` \<formatting-property\>. |
+| FORMAT 'CSV' | Use '`CSV`' `FORMAT` with `HdfsTextSimple` when
\<path-to-hdfs-file\> will reference a comma-separated value file. |
+| FORMAT 'CUSTOM' | Use the `'CUSTOM'` `FORMAT` with the
`SequenceWritable` profile. The `SequenceWritable` '`CUSTOM`' `FORMAT` supports
only the built-in `(formatter='pxfwritable_export)` (write) and
`(formatter='pxfwritable_import)` (read) \<formatting-properties\>.
+
+**Note**: When creating PXF external tables, you cannot use the `HEADER`
option in your `FORMAT` specification.
+
+## <a id="profile_hdfstextsimple"></a>Custom Options
+
+The `HdfsTextSimple` and `SequenceWritable` profiles support the following
\<custom-options\>:
+
+| Keyword | Value Description |
+|-------|-------------------------------------|
+| COMPRESSION_CODEC | The compression codec Java class name. If this
option is not provided, no data compression is performed. Supported compression
codecs include: `org.apache.hadoop.io.compress.DefaultCodec`,
`org.apache.hadoop.io.compress.BZip2Codec`, and
`org.apache.hadoop.io.compress.GzipCodec` (`HdfsTextSimple` profile only) |
+| COMPRESSION_TYPE | The compression type to employ; supported values
are `RECORD` (the default) or `BLOCK`. |
+| DATA-SCHEMA | (`SequenceWritable` profile only) The name of the
writer serialization/deserialization class. The jar file in which this class
resides must be in the PXF class path. This option has no default value. |
+| THREAD-SAFE | Boolean value determining if a table query can run in
multi-thread mode. Default value is `TRUE`, requests run in multi-threaded
mode. When set to `FALSE`, requests will be handled in a single thread.
`THREAD-SAFE` should be set appropriately when operations that are not
thread-safe are performed (i.e. compression). |
+
+## <a id="profile_hdfstextsimple"></a>HdfsTextSimple Profile
+
+Use the `HdfsTextSimple` profile when writing delimited data to a plain
text file where each row is a single record.
+
+Writable tables created using the `HdfsTextSimple` profile can use no,
record, or block compression. When compression is used, the default, gzip, and
bzip2 Hadoop compression codecs are supported:
+
+- org.apache.hadoop.io.compress.DefaultCodec
+- org.apache.hadoop.io.compress.GzipCodec
+- org.apache.hadoop.io.compress.BZip2Codec
+
+\<formatting-properties\> supported by the `HdfsTextSimple` profile
include:
+
+| Keyword | Value |
+|-------|-------------------------------------|
+| delimiter | The delimiter character to use when writing the file.
Default value is a comma `,`.|
+
+
+### <a id="profile_hdfstextsimple_writing"></a>Example: Writing Using the
HdfsTextSimple Profile
+
+This example uses the data schema introduced in [Example: Using the
HdfsTextSimple Profile] (HDFSFileDataPXF.html#profile_hdfstextsimple_query):
+
+
+| Field Name | Data Type |
+|-------|-------------------------------------|
+| location | text |
+| month | text |
+| number\_of\_orders | int |
+| total\_sales | float8 |
+
+
+Perform the following operations to use the PXF `HdfsTextSimple` 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.
+
+1. Create a writable HAWQ external table with the data schema described
above. Write to the HDFS file
`/data/pxf_examples/pxfwritable_hdfs_textsimple1`. Create the table specifying
a comma `,` as the delimiter:
+
+ ``` sql
+ gpadmin=# CREATE WRITABLE EXTERNAL TABLE
pxf_hdfs_writabletbl_1(location text, month text, num_orders int, total_sales
float8)
+ LOCATION
('pxf://namenode:51200/data/pxf_examples/pxfwritable_hdfs_textsimple1?PROFILE=HdfsTextSimple')
+ FORMAT 'TEXT' (delimiter=E',');
+ ```
+
+ The `FORMAT` subclause `delimiter` value is specified as the single
ascii comma character ','. `E` escapes the character.
--- End diff --
change ',' to (,) or `,` for readability
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