33.10. Control Functions
These functions control miscellaneous details oflibpq'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);connis a connection to the server, andencodingis 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 usingPQclientEncoding.PQsetErrorVerbosityDetermines the verbosity of messages returned by
PQerrorMessageandPQresultErrorMessage.typedef enum{ PQERRORS_TERSE, PQERRORS_DEFAULT, PQERRORS_VERBOSE} PGVerbosity;PGVerbosity PQsetErrorVerbosity(PGconn *conn, PGVerbosity verbosity);PQsetErrorVerbositysets the verbosity mode, returning the connection's previous setting. InTERSE 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). TheVERBOSE mode includes all available fields. Changing the verbosity does not affect the messages available from already-existingPGresultobjects, only subsequently-created ones. (But seePQresultVerboseErrorMessageif you want to print a previous error with a different verbosity.)PQsetErrorContextVisibilityDetermines the handling of
CONTEXTfields in messages returned byPQerrorMessageandPQresultErrorMessage.typedef enum{ PQSHOW_CONTEXT_NEVER, PQSHOW_CONTEXT_ERRORS, PQSHOW_CONTEXT_ALWAYS} PGContextVisibility;PGContextVisibility PQsetErrorContextVisibility(PGconn *conn, PGContextVisibility show_context);PQsetErrorContextVisibilitysets the context display mode, returning the connection's previous setting. This mode controls whether theCONTEXTfield is included in messages (unless the verbosity setting isTERSE, in which caseCONTEXTis never shown). TheNEVER mode never includesCONTEXT, whileALWAYS always includes it if available. InERRORS mode (the default),CONTEXTfields are included only for error messages, not for notices and warnings. Changing this mode does not affect the messages available from already-existingPGresultobjects, only subsequently-created ones. (But seePQresultVerboseErrorMessageif 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);
Note
On Windows, if thelibpq library and an application are compiled with different flags, this function call will crash the application because the internal representation of the
FILEpointers differ. Specifically, multithreaded/single-threaded, release/debug, and static/dynamic flags should be the same for the library and all applications using that library.PQuntraceDisables tracing started by
PQtrace.void PQuntrace(PGconn *conn);