Error message field of PostgreSQL

Question

Can anybody tell me what is W or where field in error messages of PostgreSQL? I read explanations in http://www.postgresql.org/docs/9.3/static/protocol-error-fields.html but I did not understand!

Answer 1

That document is defining the protocol for error fields, and it's the client's responsibility to parse and present them. (i.e. psql, JDBC or something else).

W is meant to provide the context for the error in the form of a stack trace, so a sense of where the error occurred can be reflected to the user of the client.

What is the context for this question? i.e. why do you want to know the protocol specifics?