A dialect is a different way to interpret the same CQL statement.
Examples:
- how duplicate bind variable names are handled (later in this series)
- whether `column = NULL` in LWT can return true (as is now) or
whether it always returns NULL (as in SQL)
Currently, dialect is an empty structure and will be filled in later.
It is passed to query_processor methods that also accept a CQL string,
and from there to the parser. It is part of the prepared statement cache
key, so that if the dialect is changed online, previous parses of the
statement are ignored and the statement is prepared again.
The patch is careful to pick up the dialect at the entry point (e.g.
CQL protocol server) so that the dialect doesn't change while a statement
is parsed, prepared, and cached.
(cherry picked from commit d69bf4f010)
92dd47c6d6