These functions control miscellaneous details of libpq's behavior.
PQclientEncodingReturns 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);
PQsetClientEncodingSets 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.)
     
PQtraceEnables tracing of the client/server communication to a debugging file stream.
void PQtrace(PGconn *conn, FILE *stream);
      Each line consists of: an optional timestamp, a direction indicator
      (F for messages from client to server
      or B for messages from server to client),
      message length, message type, and message contents.
      Non-message contents fields (timestamp, direction, length and message type)
      are separated by a tab. Message contents are separated by a space.
      Protocol strings are enclosed in double quotes, while strings used as data
      values are enclosed in single quotes.  Non-printable chars are printed as
      hexadecimal escapes.
      Further message-type-specific detail can be found in
      Section 53.7.
     
       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.
      
PQsetTraceFlagsControls the tracing behavior of client/server communication.
void PQsetTraceFlags(PGconn *conn, int flags);
      flags contains flag bits describing the operating mode
      of tracing.
      If flags contains PQTRACE_SUPPRESS_TIMESTAMPS,
      then the timestamp is not included when printing each message.
      If flags contains PQTRACE_REGRESS_MODE,
      then some fields are redacted when printing each message, such as object
      OIDs, to make the output more convenient to use in testing frameworks.
      This function must be called after calling PQtrace.
     
PQuntrace
      Disables tracing started by PQtrace.
void PQuntrace(PGconn *conn);