PostgreSQL: Valid variable names for functions I cannot find any definitive information on what constitutes a valid variable name in a PostgreSQL function.

I am assuming the function is written using plpgsql. I know I can use letters, numerals (apart from the first character) and underscores. Is there anything else?

Where is this documented?
This is implicitly stated in the introduction to PL/pgSQL. 


  Identifiers are implicitly converted to lower case unless double-quoted, just as they are in ordinary SQL commands.


So a PL/pgSQL variable has to comply with the rules for SQL identifiers