Re: Determining client_encoding from client locale

Here's my first attempt at setting client_encoding automatically from
locale.

It adds a new conninfo parameter to libpq, "client_encoding". If set to
"auto", libpq uses the encoding as returned by
pg_get_encoding_from_locale(). Any other value is passed through to the
server as is.

psql is modified to set "client_encoding=auto", unless overridden by
PGCLIENTENCODING.

BTW, I had to modify psql to use PQconnectdb() instead of
PQsetdblogin(), so that it can pass the extra parameter. I found it a
bit laboursome to construct the conninfo string with proper escaping,
just to have libpq parse and split it into components again. Could we
have a version of PQconnectdb() with an API more suited for setting the
params programmatically? The PQsetdbLogin() approach doesn't scale as
parameters are added/removed in future versions, but we could have
something like this:

PGconn *PQconnectParams(const char **params)

Where "params" is an array with an even number of parameters, forming
key/value pairs. Usage example:

char *connparams[] = {
"dbname", "mydb",
"user", username,
NULL /* terminate with NULL */
};
conn = PQconnectParams(connparams);

This is similar to what I did internally in psql in the attached patch.

Another idea is to use an array of PQconninfoOption structs:

PQconn *PQconnectParams(PQconninfoOption *params);

This would be quite natural since that's the format returned by
PQconnDefaults() and PQconninfoParse(), but a bit more cumbersome to use
in applications that don't use those functions, as in the previous example.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com