These functions control miscellaneous details of libpq's behavior.
PQclientEncoding
     
    Returns the client encoding.
int PQclientEncoding(const PGconn *conn);
      Note that it returns the encoding ID, not a symbolic string
      such as EUC_JP. If unsuccessful, it returns -1.
      To convert an encoding ID to an encoding name, you
      can use:
char *pg_encoding_to_char(int encoding_id);
PQsetClientEncoding
     
    Sets the client encoding.
int PQsetClientEncoding(PGconn *conn, const char *encoding);
      conn is a connection to the server,
      and encoding is the encoding you want to
      use. If the function successfully sets the encoding, it returns 0,
      otherwise -1. The current encoding for this connection can be
      determined by using PQclientEncoding.
     
PQsetErrorVerbosity
     
    
      Determines the verbosity of messages returned by
      PQerrorMessage and PQresultErrorMessage.
typedef enum
{
    PQERRORS_TERSE,
    PQERRORS_DEFAULT,
    PQERRORS_VERBOSE,
    PQERRORS_SQLSTATE
} PGVerbosity;
PGVerbosity PQsetErrorVerbosity(PGconn *conn, PGVerbosity verbosity);
      PQsetErrorVerbosity sets the verbosity mode,
      returning the connection's previous setting.
      In TERSE mode, returned messages include
      severity, primary text, and position only; this will normally fit on a
      single line.  The DEFAULT mode produces messages
      that include the above plus any detail, hint, or context fields (these
      might span multiple lines).  The VERBOSE mode
      includes all available fields.  The SQLSTATE
      mode includes only the error severity and the SQLSTATE
      error code, if one is available (if not, the output is like
      TERSE mode).
     
      Changing the verbosity setting does not affect the messages available
      from already-existing PGresult objects, only
      subsequently-created ones.
      (But see PQresultVerboseErrorMessage if you
      want to print a previous error with a different verbosity.)
     
PQsetErrorContextVisibility
     
    
      Determines the handling of CONTEXT fields in messages
      returned by PQerrorMessage
      and PQresultErrorMessage.
typedef enum
{
    PQSHOW_CONTEXT_NEVER,
    PQSHOW_CONTEXT_ERRORS,
    PQSHOW_CONTEXT_ALWAYS
} PGContextVisibility;
PGContextVisibility PQsetErrorContextVisibility(PGconn *conn, PGContextVisibility show_context);
      PQsetErrorContextVisibility sets the context display mode,
      returning the connection's previous setting.  This mode controls
      whether the CONTEXT field is included in messages.
      The NEVER mode
      never includes CONTEXT, while ALWAYS always
      includes it if available.  In ERRORS mode (the
      default), CONTEXT fields are included only in error
      messages, not in notices and warnings.
      (However, if the verbosity setting is TERSE
      or SQLSTATE, CONTEXT fields
      are omitted regardless of the context display mode.)
     
      Changing this mode does not
      affect the messages available from
      already-existing PGresult objects, only
      subsequently-created ones.
      (But see PQresultVerboseErrorMessage if you
      want to print a previous error with a different display mode.)
     
PQtrace
     
    Enables tracing of the client/server communication to a debugging file stream.
void PQtrace(PGconn *conn, FILE *stream);
       On Windows, if the libpq library and an application are
       compiled with different flags, this function call will crash the
       application because the internal representation of the FILE
       pointers differ.  Specifically, multithreaded/single-threaded,
       release/debug, and static/dynamic flags should be the same for the
       library and all applications using that library.
      
PQuntrace
     
    
      Disables tracing started by PQtrace.
void PQuntrace(PGconn *conn);