Some rare questions

Hi,

I am writing a driver for PostgreSQL, and I need some rare info:


How can I query the collation/locale of the database cluster?

What can be the maximal length of the indexed part of the string. So I have
a text field, and I create an index on it. How long can be one index key max
in this case?

How deep can be the subquery nesting?

How long can be the index key?

What is maximal number of compare operations for a single query?

What is maximal length of a query text (characters) ?

What is maximal length of a row (bytes) ?

What is the maximal length of char/varchar/text ?

What operations cannot be rolled back with Rollback ?

Thanks in advance,
Otto