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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>34.11. Control Functions</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="libpq-copy.html" title="34.10. Functions Associated with the COPY Command" /><link rel="next" href="libpq-misc.html" title="34.12. Miscellaneous Functions" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">34.11. Control Functions</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="libpq-copy.html" title="34.10. Functions Associated with the COPY Command">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="libpq.html" title="Chapter 34. libpq — C Library">Up</a></td><th width="60%" align="center">Chapter 34. <span class="application">libpq</span> — C Library</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="libpq-misc.html" title="34.12. Miscellaneous Functions">Next</a></td></tr></table><hr /></div><div class="sect1" id="LIBPQ-CONTROL"><div class="titlepage"><div><div><h2 class="title" style="clear: both">34.11. Control Functions</h2></div></div></div><p>
These functions control miscellaneous details of <span class="application">libpq</span>'s
behavior.
</p><div class="variablelist"><dl class="variablelist"><dt id="LIBPQ-PQCLIENTENCODING"><span class="term"><code class="function">PQclientEncoding</code><a id="id-1.7.3.18.3.1.1.2" class="indexterm"></a></span></dt><dd><p>
Returns the client encoding.
</p><pre class="synopsis">
int PQclientEncoding(const PGconn *<em class="replaceable"><code>conn</code></em>);
</pre><p>
Note that it returns the encoding ID, not a symbolic string
such as <code class="literal">EUC_JP</code>. If unsuccessful, it returns -1.
To convert an encoding ID to an encoding name, you
can use:
</p><pre class="synopsis">
char *pg_encoding_to_char(int <em class="replaceable"><code>encoding_id</code></em>);
</pre><p>
</p></dd><dt id="LIBPQ-PQSETCLIENTENCODING"><span class="term"><code class="function">PQsetClientEncoding</code><a id="id-1.7.3.18.3.2.1.2" class="indexterm"></a></span></dt><dd><p>
Sets the client encoding.
</p><pre class="synopsis">
int PQsetClientEncoding(PGconn *<em class="replaceable"><code>conn</code></em>, const char *<em class="replaceable"><code>encoding</code></em>);
</pre><p>
<em class="replaceable"><code>conn</code></em> is a connection to the server,
and <em class="replaceable"><code>encoding</code></em> 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 <a class="xref" href="libpq-control.html#LIBPQ-PQCLIENTENCODING"><code class="function">PQclientEncoding</code></a>.
</p></dd><dt id="LIBPQ-PQSETERRORVERBOSITY"><span class="term"><code class="function">PQsetErrorVerbosity</code><a id="id-1.7.3.18.3.3.1.2" class="indexterm"></a></span></dt><dd><p>
Determines the verbosity of messages returned by
<a class="xref" href="libpq-status.html#LIBPQ-PQERRORMESSAGE"><code class="function">PQerrorMessage</code></a> and <a class="xref" href="libpq-exec.html#LIBPQ-PQRESULTERRORMESSAGE"><code class="function">PQresultErrorMessage</code></a>.
</p><pre class="synopsis">
typedef enum
{
PQERRORS_TERSE,
PQERRORS_DEFAULT,
PQERRORS_VERBOSE,
PQERRORS_SQLSTATE
} PGVerbosity;
PGVerbosity PQsetErrorVerbosity(PGconn *conn, PGVerbosity verbosity);
</pre><p>
<a class="xref" href="libpq-control.html#LIBPQ-PQSETERRORVERBOSITY"><code class="function">PQsetErrorVerbosity</code></a> sets the verbosity mode,
returning the connection's previous setting.
In <em class="firstterm">TERSE</em> mode, returned messages include
severity, primary text, and position only; this will normally fit on a
single line. The <em class="firstterm">DEFAULT</em> mode produces messages
that include the above plus any detail, hint, or context fields (these
might span multiple lines). The <em class="firstterm">VERBOSE</em> mode
includes all available fields. The <em class="firstterm">SQLSTATE</em>
mode includes only the error severity and the <code class="symbol">SQLSTATE</code>
error code, if one is available (if not, the output is like
<em class="firstterm">TERSE</em> mode).
</p><p>
Changing the verbosity setting does not affect the messages available
from already-existing <code class="structname">PGresult</code> objects, only
subsequently-created ones.
(But see <a class="xref" href="libpq-exec.html#LIBPQ-PQRESULTVERBOSEERRORMESSAGE"><code class="function">PQresultVerboseErrorMessage</code></a> if you
want to print a previous error with a different verbosity.)
</p></dd><dt id="LIBPQ-PQSETERRORCONTEXTVISIBILITY"><span class="term"><code class="function">PQsetErrorContextVisibility</code><a id="id-1.7.3.18.3.4.1.2" class="indexterm"></a></span></dt><dd><p>
Determines the handling of <code class="literal">CONTEXT</code> fields in messages
returned by <a class="xref" href="libpq-status.html#LIBPQ-PQERRORMESSAGE"><code class="function">PQerrorMessage</code></a>
and <a class="xref" href="libpq-exec.html#LIBPQ-PQRESULTERRORMESSAGE"><code class="function">PQresultErrorMessage</code></a>.
</p><pre class="synopsis">
typedef enum
{
PQSHOW_CONTEXT_NEVER,
PQSHOW_CONTEXT_ERRORS,
PQSHOW_CONTEXT_ALWAYS
} PGContextVisibility;
PGContextVisibility PQsetErrorContextVisibility(PGconn *conn, PGContextVisibility show_context);
</pre><p>
<a class="xref" href="libpq-control.html#LIBPQ-PQSETERRORCONTEXTVISIBILITY"><code class="function">PQsetErrorContextVisibility</code></a> sets the context display mode,
returning the connection's previous setting. This mode controls
whether the <code class="literal">CONTEXT</code> field is included in messages.
The <em class="firstterm">NEVER</em> mode
never includes <code class="literal">CONTEXT</code>, while <em class="firstterm">ALWAYS</em> always
includes it if available. In <em class="firstterm">ERRORS</em> mode (the
default), <code class="literal">CONTEXT</code> fields are included only in error
messages, not in notices and warnings.
(However, if the verbosity setting is <em class="firstterm">TERSE</em>
or <em class="firstterm">SQLSTATE</em>, <code class="literal">CONTEXT</code> fields
are omitted regardless of the context display mode.)
</p><p>
Changing this mode does not
affect the messages available from
already-existing <code class="structname">PGresult</code> objects, only
subsequently-created ones.
(But see <a class="xref" href="libpq-exec.html#LIBPQ-PQRESULTVERBOSEERRORMESSAGE"><code class="function">PQresultVerboseErrorMessage</code></a> if you
want to print a previous error with a different display mode.)
</p></dd><dt id="LIBPQ-PQTRACE"><span class="term"><code class="function">PQtrace</code><a id="id-1.7.3.18.3.5.1.2" class="indexterm"></a></span></dt><dd><p>
Enables tracing of the client/server communication to a debugging file
stream.
</p><pre class="synopsis">
void PQtrace(PGconn *conn, FILE *stream);
</pre><p>
</p><p>
Each line consists of: an optional timestamp, a direction indicator
(<code class="literal">F</code> for messages from client to server
or <code class="literal">B</code> 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
<a class="xref" href="protocol-message-formats.html" title="55.7. Message Formats">Section 55.7</a>.
</p><div class="note"><h3 class="title">Note</h3><p>
On Windows, if the <span class="application">libpq</span> library and an application are
compiled with different flags, this function call will crash the
application because the internal representation of the <code class="literal">FILE</code>
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.
</p></div></dd><dt id="LIBPQ-PQSETTRACEFLAGS"><span class="term"><code class="function">PQsetTraceFlags</code><a id="id-1.7.3.18.3.6.1.2" class="indexterm"></a></span></dt><dd><p>
Controls the tracing behavior of client/server communication.
</p><pre class="synopsis">
void PQsetTraceFlags(PGconn *conn, int flags);
</pre><p>
</p><p>
<code class="literal">flags</code> contains flag bits describing the operating mode
of tracing.
If <code class="literal">flags</code> contains <code class="literal">PQTRACE_SUPPRESS_TIMESTAMPS</code>,
then the timestamp is not included when printing each message.
If <code class="literal">flags</code> contains <code class="literal">PQTRACE_REGRESS_MODE</code>,
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 <code class="function">PQtrace</code>.
</p></dd><dt id="LIBPQ-PQUNTRACE"><span class="term"><code class="function">PQuntrace</code><a id="id-1.7.3.18.3.7.1.2" class="indexterm"></a></span></dt><dd><p>
Disables tracing started by <a class="xref" href="libpq-control.html#LIBPQ-PQTRACE"><code class="function">PQtrace</code></a>.
</p><pre class="synopsis">
void PQuntrace(PGconn *conn);
</pre><p>
</p></dd></dl></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="libpq-copy.html" title="34.10. Functions Associated with the COPY Command">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="libpq.html" title="Chapter 34. libpq — C Library">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="libpq-misc.html" title="34.12. Miscellaneous Functions">Next</a></td></tr><tr><td width="40%" align="left" valign="top">34.10. Functions Associated with the <code class="command">COPY</code> Command </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.4 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 34.12. Miscellaneous Functions</td></tr></table></div></body></html>
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