How to read config data in UDF

[David L Lambert]

I'm designing a MySQL UDF (or possibly family of UDFs) to accomplish a certain task. The UDF depends on some "configuration information" (among other things, the hostname for a server). I'd rather not pass that in as an argument to every function call. I can think of a few ways to do it...

1. As a set of environment variables, read them with getenv()

2. As a plain-text configuration file in a well-known place (perhaps "/etc/mysql", or the mysql data directory), and read and parse it in xxx_init()

3. As a table-row in a new table in the `mysql` schema

Any advice on the benefits and drawbacks of the various options?

For option 2, is there a server variable I should consider for that "well-known place" instead of hard-coding it? If so, what's the proper way to read a server veriable from within a C++ UDF?

For option 3, what's the proper way to read one row from one table from within a C++ UDF?