PostgreSQL

34.10. Control Functions
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34.10. Control Functions

These functions control miscellaneous details of libpq’s behavior.

[.term]#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);

[.term]#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+`.
[.term]#`+PQsetErrorVerbosity+` ::
  Determines the verbosity of messages returned by `+PQerrorMessage+` and `+PQresultErrorMessage+`.
  +

typedef enum
{
    PQERRORS_TERSE,
    PQERRORS_DEFAULT,
    PQERRORS_VERBOSE
} 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. Changing the verbosity 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.)
[.term]#`+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 (unless the verbosity setting is _TERSE_, in which case `+CONTEXT+` is never shown). The _NEVER_ mode never includes `+CONTEXT+`, while _ALWAYS_ always includes it if available. In _ERRORS_ mode (the default), `+CONTEXT+` fields are included only for error messages, not for notices and warnings. 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.)
[.term]#`+PQtrace+` ::
  Enables tracing of the client/server communication to a debugging file stream.
  +

void PQtrace(PGconn *conn, FILE *stream);

+
[NOTE]
====
==== Note

  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.
  ====
[.term]#`+PQuntrace+` ::
  Disables tracing started by `+PQtrace+`.
  +

void PQuntrace(PGconn *conn);

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34.9. Functions Associated with the `COPY` Command	Home	34.11. Miscellaneous Functions

34.9. Functions Associated with the COPY Command

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34.11. Miscellaneous Functions