Github user janebeckman commented on a diff in the pull request:
https://github.com/apache/incubator-hawq-docs/pull/85#discussion_r95908029
--- Diff: markdown/reference/sql/CREATE-CONVERSION.html.md.erb ---
@@ -0,0 +1,72 @@
+---
+title: CREATE CONVERSION
+---
+
+Defines a new encoding conversion.
+
+## <a id="topic1__section2"></a>Synopsis
+
+``` pre
+CREATE [DEFAULT] CONVERSION name FOR source_encoding TO
+ dest_encoding FROM funcname
+```
+
+## <a id="topic1__section3"></a>Description
+
+`CREATE CONVERSION` defines a new conversion between character set
encodings. Conversion names may be used in the convert function to specify a
particular encoding conversion. Also, conversions that are marked `DEFAULT` can
be used for automatic encoding conversion between client and server. For this
purpose, two conversions, from encoding A to B and from encoding B to A, must
be defined.
+
+To create a conversion, you must have `EXECUTE` privilege on the function
and `CREATE` privilege on the destination schema.
+
+
+## <a id="topic1__section4"></a>Parameters
+
+<dt>DEFAULT</dt>
+<dd>Indicates that this conversion is the default for this particular
source to destination encoding. There should be only one default encoding in a
schema for the encoding pair.</dd>
+
+<dt>\<name\> </dt>
+<dd>The name of the conversion. The conversion name may be
schema-qualified. If it is not, the conversion is defined in the current
schema. The conversion name must be unique within a schema.</dd>
+
+<dt>\<source_encoding\> </dt>
+<dd>The source encoding name.</dd>
+
+<dt>\<dest_encoding\> </dt>
+<dd>The destination encoding name.</dd>
+
+<dt>\<funcname\> </dt>
+<dd>The function used to perform the conversion. The function name may be
schema-qualified. If it is not, the function will be looked up in the path. The
function must have the following signature:</dd>
+
+``` pre
+conv_proc(
+ integer, -- source encoding ID
+ integer, -- destination encoding ID
+ cstring, -- source string (null terminated C string)
+ internal, -- destination (fill with a null terminated C string)
+ integer -- source string length
+) RETURNS void;
+```
+
+## <a id="topic1__section5"></a>Notes
+
+For this release of HAWQ, user-defined functions used in a user-defined
cast must be defined as `IMMUTABLE`. Any compiled code (shared library files)
for custom functions must be placed in the same location on every host in your
HAWQ array (master and all segments). This location must also be in the
`LD_LIBRARY_PATH` so that the server can locate the files.
+
+
+## <a id="topic1__section6"></a>Examples
+
+To create a conversion from encoding `UTF8` to `LATIN1` using `myfunc`:
+
+``` pre
+CREATE CONVERSION myconv FOR 'UTF8' TO 'LATIN1' FROM myfunc;
+```
+
+## <a id="topic1__section7"></a>Compatibility
+
+There is no CREATE CONVERSION statement in the SQL standard.
+
+## <a id="topic1__section8"></a>See Also
+
+[DROP CONVERSION](DROP-CONVERSION.html), [CREATE
FUNCTION](CREATE-FUNCTION.html)
--- End diff --
I didn't ask about that one, but it would make sense.
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