MySQL Bugs: #28907: UDF_ARGS->attributes and UDF_ARGS->attribute

Bug #28907	UDF_ARGS->attributes and UDF_ARGS->attribute_lengths not documented
Submitted:	5 Jun 2007 20:31	Modified:	26 Jul 2007 17:18
Reporter:	Roland Bouman	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Documentation	Severity:	S3 (Non-critical)
Version:	4.1 and beyond	OS:	Any
Assigned to:	Paul DuBois	CPU Architecture:	Any
Tags:	udf, UDF_ARGS, UDF_ARGS->attribute_lengths, UDF_ARGS->attributes

Description:
The description of UDF argument processing at

http://dev.mysql.com/doc/refman/5.1/en/udf-arguments.html

does not describe the attributes and attribute_lenghts members of the UDF_ARGS structure passed to UDFs. 

UDF_ARGS->attributes[n] contains the "name" of the n+1th argument passed to the UDF (n=0 for first argument, n=1 for second and so on and so forth)

UDF_ARGS->attribute_lengths[n] contains the string length of UDF_ARGS->attributes[n]

How to repeat:
select my_udf(expr1, expr2 AS alias1, expr3 alias2)

UDF_ARGS->attributes[0] = "expr1"
UDF_ARGS->attribute_lengths[0] = 5

UDF_ARGS->attributes[1] = "alias1"
UDF_ARGS->attribute_lengths[1] = 6

UDF_ARGS->attributes[2] = "alias2"
UDF_ARGS->attribute_lengths[2] = 6

so, the "name" of an UDF argument is 
- the expression text when no alias is specified
- the alias if an alias is specified.

Aliases may be specified as usual, so the keyword "AS" is optional.
(I believe that passing aliases for function arguments is not part of any standard)

Suggested fix:
Please document this behaviour. It is very convenient in a number of cases, for example when mapping data from the database to another format:

select udf_xml_attributes(column1, column2, ...) 

->

'column1="value of column1" column2="value of column2"'

Thank you for a reasonable documentation request.

Thank you for your bug report. This issue has been addressed in the documentation. The updated documentation will appear on our website shortly, and will be included in the next release of the relevant products.