diff options
Diffstat (limited to 'doc/src/sgml/html/libpq-misc.html')
| -rw-r--r-- | doc/src/sgml/html/libpq-misc.html | 233 |
1 files changed, 233 insertions, 0 deletions
diff --git a/doc/src/sgml/html/libpq-misc.html b/doc/src/sgml/html/libpq-misc.html new file mode 100644 index 0000000..c9bc085 --- /dev/null +++ b/doc/src/sgml/html/libpq-misc.html @@ -0,0 +1,233 @@ +<?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>34.12. Miscellaneous 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-control.html" title="34.11. Control Functions" /><link rel="next" href="libpq-notice-processing.html" title="34.13. Notice Processing" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">34.12. Miscellaneous Functions</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="libpq-control.html" title="34.11. Control Functions">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 15.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="libpq-notice-processing.html" title="34.13. Notice Processing">Next</a></td></tr></table><hr /></div><div class="sect1" id="LIBPQ-MISC"><div class="titlepage"><div><div><h2 class="title" style="clear: both">34.12. Miscellaneous Functions</h2></div></div></div><p> + As always, there are some functions that just don't fit anywhere. + </p><div class="variablelist"><dl class="variablelist"><dt id="LIBPQ-PQFREEMEM"><span class="term"><code class="function">PQfreemem</code><a id="id-1.7.3.19.3.1.1.2" class="indexterm"></a></span></dt><dd><p> + Frees memory allocated by <span class="application">libpq</span>. +</p><pre class="synopsis"> +void PQfreemem(void *ptr); +</pre><p> + </p><p> + Frees memory allocated by <span class="application">libpq</span>, particularly + <a class="xref" href="libpq-exec.html#LIBPQ-PQESCAPEBYTEACONN"><code class="function">PQescapeByteaConn</code></a>, + <a class="xref" href="libpq-exec.html#LIBPQ-PQESCAPEBYTEA"><code class="function">PQescapeBytea</code></a>, + <a class="xref" href="libpq-exec.html#LIBPQ-PQUNESCAPEBYTEA"><code class="function">PQunescapeBytea</code></a>, + and <code class="function">PQnotifies</code>. + It is particularly important that this function, rather than + <code class="function">free()</code>, be used on Microsoft Windows. This is because + allocating memory in a DLL and releasing it in the application works + only if multithreaded/single-threaded, release/debug, and static/dynamic + flags are the same for the DLL and the application. On non-Microsoft + Windows platforms, this function is the same as the standard library + function <code class="function">free()</code>. + </p></dd><dt id="LIBPQ-PQCONNINFOFREE"><span class="term"><code class="function">PQconninfoFree</code><a id="id-1.7.3.19.3.2.1.2" class="indexterm"></a></span></dt><dd><p> + Frees the data structures allocated by + <a class="xref" href="libpq-connect.html#LIBPQ-PQCONNDEFAULTS"><code class="function">PQconndefaults</code></a> or <a class="xref" href="libpq-connect.html#LIBPQ-PQCONNINFOPARSE"><code class="function">PQconninfoParse</code></a>. +</p><pre class="synopsis"> +void PQconninfoFree(PQconninfoOption *connOptions); +</pre><p> + </p><p> + A simple <a class="xref" href="libpq-misc.html#LIBPQ-PQFREEMEM"><code class="function">PQfreemem</code></a> will not do for this, since + the array contains references to subsidiary strings. + </p></dd><dt id="LIBPQ-PQENCRYPTPASSWORDCONN"><span class="term"><code class="function">PQencryptPasswordConn</code><a id="id-1.7.3.19.3.3.1.2" class="indexterm"></a></span></dt><dd><p> + Prepares the encrypted form of a <span class="productname">PostgreSQL</span> password. +</p><pre class="synopsis"> +char *PQencryptPasswordConn(PGconn *conn, const char *passwd, const char *user, const char *algorithm); +</pre><p> + This function is intended to be used by client applications that + wish to send commands like <code class="literal">ALTER USER joe PASSWORD + 'pwd'</code>. It is good practice not to send the original cleartext + password in such a command, because it might be exposed in command + logs, activity displays, and so on. Instead, use this function to + convert the password to encrypted form before it is sent. + </p><p> + The <em class="parameter"><code>passwd</code></em> and <em class="parameter"><code>user</code></em> arguments + are the cleartext password, and the SQL name of the user it is for. + <em class="parameter"><code>algorithm</code></em> specifies the encryption algorithm + to use to encrypt the password. Currently supported algorithms are + <code class="literal">md5</code> and <code class="literal">scram-sha-256</code> (<code class="literal">on</code> and + <code class="literal">off</code> are also accepted as aliases for <code class="literal">md5</code>, for + compatibility with older server versions). Note that support for + <code class="literal">scram-sha-256</code> was introduced in <span class="productname">PostgreSQL</span> + version 10, and will not work correctly with older server versions. If + <em class="parameter"><code>algorithm</code></em> is <code class="symbol">NULL</code>, this function will query + the server for the current value of the + <a class="xref" href="runtime-config-connection.html#GUC-PASSWORD-ENCRYPTION">password_encryption</a> setting. That can block, and + will fail if the current transaction is aborted, or if the connection + is busy executing another query. If you wish to use the default + algorithm for the server but want to avoid blocking, query + <code class="varname">password_encryption</code> yourself before calling + <a class="xref" href="libpq-misc.html#LIBPQ-PQENCRYPTPASSWORDCONN"><code class="function">PQencryptPasswordConn</code></a>, and pass that value as the + <em class="parameter"><code>algorithm</code></em>. + </p><p> + The return value is a string allocated by <code class="function">malloc</code>. + The caller can assume the string doesn't contain any special characters + that would require escaping. Use <a class="xref" href="libpq-misc.html#LIBPQ-PQFREEMEM"><code class="function">PQfreemem</code></a> to free the + result when done with it. On error, returns <code class="symbol">NULL</code>, and + a suitable message is stored in the connection object. + </p></dd><dt id="LIBPQ-PQENCRYPTPASSWORD"><span class="term"><code class="function">PQencryptPassword</code><a id="id-1.7.3.19.3.4.1.2" class="indexterm"></a></span></dt><dd><p> + Prepares the md5-encrypted form of a <span class="productname">PostgreSQL</span> password. +</p><pre class="synopsis"> +char *PQencryptPassword(const char *passwd, const char *user); +</pre><p> + <a class="xref" href="libpq-misc.html#LIBPQ-PQENCRYPTPASSWORD"><code class="function">PQencryptPassword</code></a> is an older, deprecated version of + <a class="xref" href="libpq-misc.html#LIBPQ-PQENCRYPTPASSWORDCONN"><code class="function">PQencryptPasswordConn</code></a>. The difference is that + <a class="xref" href="libpq-misc.html#LIBPQ-PQENCRYPTPASSWORD"><code class="function">PQencryptPassword</code></a> does not + require a connection object, and <code class="literal">md5</code> is always used as the + encryption algorithm. + </p></dd><dt id="LIBPQ-PQMAKEEMPTYPGRESULT"><span class="term"><code class="function">PQmakeEmptyPGresult</code><a id="id-1.7.3.19.3.5.1.2" class="indexterm"></a></span></dt><dd><p> + Constructs an empty <code class="structname">PGresult</code> object with the given status. +</p><pre class="synopsis"> +PGresult *PQmakeEmptyPGresult(PGconn *conn, ExecStatusType status); +</pre><p> + </p><p> + This is <span class="application">libpq</span>'s internal function to allocate and + initialize an empty <code class="structname">PGresult</code> object. This + function returns <code class="symbol">NULL</code> if memory could not be allocated. It is + exported because some applications find it useful to generate result + objects (particularly objects with error status) themselves. If + <em class="parameter"><code>conn</code></em> is not null and <em class="parameter"><code>status</code></em> + indicates an error, the current error message of the specified + connection is copied into the <code class="structname">PGresult</code>. + Also, if <em class="parameter"><code>conn</code></em> is not null, any event procedures + registered in the connection are copied into the + <code class="structname">PGresult</code>. (They do not get + <code class="literal">PGEVT_RESULTCREATE</code> calls, but see + <a class="xref" href="libpq-misc.html#LIBPQ-PQFIRERESULTCREATEEVENTS"><code class="function">PQfireResultCreateEvents</code></a>.) + Note that <a class="xref" href="libpq-exec.html#LIBPQ-PQCLEAR"><code class="function">PQclear</code></a> should eventually be called + on the object, just as with a <code class="structname">PGresult</code> + returned by <span class="application">libpq</span> itself. + </p></dd><dt id="LIBPQ-PQFIRERESULTCREATEEVENTS"><span class="term"><code class="function">PQfireResultCreateEvents</code><a id="id-1.7.3.19.3.6.1.2" class="indexterm"></a></span></dt><dd><p> + Fires a <code class="literal">PGEVT_RESULTCREATE</code> event (see <a class="xref" href="libpq-events.html" title="34.14. Event System">Section 34.14</a>) for each event procedure registered in the + <code class="structname">PGresult</code> object. Returns non-zero for success, + zero if any event procedure fails. + +</p><pre class="synopsis"> +int PQfireResultCreateEvents(PGconn *conn, PGresult *res); +</pre><p> + </p><p> + The <code class="literal">conn</code> argument is passed through to event procedures + but not used directly. It can be <code class="symbol">NULL</code> if the event + procedures won't use it. + </p><p> + Event procedures that have already received a + <code class="literal">PGEVT_RESULTCREATE</code> or <code class="literal">PGEVT_RESULTCOPY</code> event + for this object are not fired again. + </p><p> + The main reason that this function is separate from + <a class="xref" href="libpq-misc.html#LIBPQ-PQMAKEEMPTYPGRESULT"><code class="function">PQmakeEmptyPGresult</code></a> is that it is often appropriate + to create a <code class="structname">PGresult</code> and fill it with data + before invoking the event procedures. + </p></dd><dt id="LIBPQ-PQCOPYRESULT"><span class="term"><code class="function">PQcopyResult</code><a id="id-1.7.3.19.3.7.1.2" class="indexterm"></a></span></dt><dd><p> + Makes a copy of a <code class="structname">PGresult</code> object. The copy is + not linked to the source result in any way and + <a class="xref" href="libpq-exec.html#LIBPQ-PQCLEAR"><code class="function">PQclear</code></a> must be called when the copy is no longer + needed. If the function fails, <code class="symbol">NULL</code> is returned. + +</p><pre class="synopsis"> +PGresult *PQcopyResult(const PGresult *src, int flags); +</pre><p> + </p><p> + This is not intended to make an exact copy. The returned result is + always put into <code class="literal">PGRES_TUPLES_OK</code> status, and does not + copy any error message in the source. (It does copy the command status + string, however.) The <em class="parameter"><code>flags</code></em> argument determines + what else is copied. It is a bitwise OR of several flags. + <code class="literal">PG_COPYRES_ATTRS</code> specifies copying the source + result's attributes (column definitions). + <code class="literal">PG_COPYRES_TUPLES</code> specifies copying the source + result's tuples. (This implies copying the attributes, too.) + <code class="literal">PG_COPYRES_NOTICEHOOKS</code> specifies + copying the source result's notify hooks. + <code class="literal">PG_COPYRES_EVENTS</code> specifies copying the source + result's events. (But any instance data associated with the source + is not copied.) + The event procedures receive <code class="literal">PGEVT_RESULTCOPY</code> events. + </p></dd><dt id="LIBPQ-PQSETRESULTATTRS"><span class="term"><code class="function">PQsetResultAttrs</code><a id="id-1.7.3.19.3.8.1.2" class="indexterm"></a></span></dt><dd><p> + Sets the attributes of a <code class="structname">PGresult</code> object. +</p><pre class="synopsis"> +int PQsetResultAttrs(PGresult *res, int numAttributes, PGresAttDesc *attDescs); +</pre><p> + </p><p> + The provided <em class="parameter"><code>attDescs</code></em> are copied into the result. + If the <em class="parameter"><code>attDescs</code></em> pointer is <code class="symbol">NULL</code> or + <em class="parameter"><code>numAttributes</code></em> is less than one, the request is + ignored and the function succeeds. If <em class="parameter"><code>res</code></em> + already contains attributes, the function will fail. If the function + fails, the return value is zero. If the function succeeds, the return + value is non-zero. + </p></dd><dt id="LIBPQ-PQSETVALUE"><span class="term"><code class="function">PQsetvalue</code><a id="id-1.7.3.19.3.9.1.2" class="indexterm"></a></span></dt><dd><p> + Sets a tuple field value of a <code class="structname">PGresult</code> object. +</p><pre class="synopsis"> +int PQsetvalue(PGresult *res, int tup_num, int field_num, char *value, int len); +</pre><p> + </p><p> + The function will automatically grow the result's internal tuples array + as needed. However, the <em class="parameter"><code>tup_num</code></em> argument must be + less than or equal to <a class="xref" href="libpq-exec.html#LIBPQ-PQNTUPLES"><code class="function">PQntuples</code></a>, meaning this + function can only grow the tuples array one tuple at a time. But any + field of any existing tuple can be modified in any order. If a value at + <em class="parameter"><code>field_num</code></em> already exists, it will be overwritten. + If <em class="parameter"><code>len</code></em> is -1 or + <em class="parameter"><code>value</code></em> is <code class="symbol">NULL</code>, the field value + will be set to an SQL null value. The + <em class="parameter"><code>value</code></em> is copied into the result's private storage, + thus is no longer needed after the function + returns. If the function fails, the return value is zero. If the + function succeeds, the return value is non-zero. + </p></dd><dt id="LIBPQ-PQRESULTALLOC"><span class="term"><code class="function">PQresultAlloc</code><a id="id-1.7.3.19.3.10.1.2" class="indexterm"></a></span></dt><dd><p> + Allocate subsidiary storage for a <code class="structname">PGresult</code> object. +</p><pre class="synopsis"> +void *PQresultAlloc(PGresult *res, size_t nBytes); +</pre><p> + </p><p> + Any memory allocated with this function will be freed when + <em class="parameter"><code>res</code></em> is cleared. If the function fails, + the return value is <code class="symbol">NULL</code>. The result is + guaranteed to be adequately aligned for any type of data, + just as for <code class="function">malloc</code>. + </p></dd><dt id="LIBPQ-PQRESULTMEMORYSIZE"><span class="term"><code class="function">PQresultMemorySize</code><a id="id-1.7.3.19.3.11.1.2" class="indexterm"></a></span></dt><dd><p> + Retrieves the number of bytes allocated for + a <code class="structname">PGresult</code> object. +</p><pre class="synopsis"> +size_t PQresultMemorySize(const PGresult *res); +</pre><p> + </p><p> + This value is the sum of all <code class="function">malloc</code> requests + associated with the <code class="structname">PGresult</code> object, that is, + all the space that will be freed by <a class="xref" href="libpq-exec.html#LIBPQ-PQCLEAR"><code class="function">PQclear</code></a>. + This information can be useful for managing memory consumption. + </p></dd><dt id="LIBPQ-PQLIBVERSION"><span class="term"><code class="function">PQlibVersion</code><a id="id-1.7.3.19.3.12.1.2" class="indexterm"></a></span></dt><dd><p> + Return the version of <span class="productname">libpq</span> that is being used. +</p><pre class="synopsis"> +int PQlibVersion(void); +</pre><p> + </p><p> + The result of this function can be used to determine, at + run time, whether specific functionality is available in the currently + loaded version of libpq. The function can be used, for example, + to determine which connection options are available in + <a class="xref" href="libpq-connect.html#LIBPQ-PQCONNECTDB"><code class="function">PQconnectdb</code></a>. + </p><p> + The result is formed by multiplying the library's major version + number by 10000 and adding the minor version number. For example, + version 10.1 will be returned as 100001, and version 11.0 will be + returned as 110000. + </p><p> + Prior to major version 10, <span class="productname">PostgreSQL</span> used + three-part version numbers in which the first two parts together + represented the major version. For those + versions, <a class="xref" href="libpq-misc.html#LIBPQ-PQLIBVERSION"><code class="function">PQlibVersion</code></a> uses two digits for each + part; for example version 9.1.5 will be returned as 90105, and + version 9.2.0 will be returned as 90200. + </p><p> + Therefore, for purposes of determining feature compatibility, + applications should divide the result of <a class="xref" href="libpq-misc.html#LIBPQ-PQLIBVERSION"><code class="function">PQlibVersion</code></a> + by 100 not 10000 to determine a logical major version number. + In all release series, only the last two digits differ between + minor releases (bug-fix releases). + </p><div class="note"><h3 class="title">Note</h3><p> + This function appeared in <span class="productname">PostgreSQL</span> version 9.1, so + it cannot be used to detect required functionality in earlier + versions, since calling it will create a link dependency + on version 9.1 or later. + </p></div></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-control.html" title="34.11. Control Functions">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-notice-processing.html" title="34.13. Notice Processing">Next</a></td></tr><tr><td width="40%" align="left" valign="top">34.11. Control Functions </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 34.13. Notice Processing</td></tr></table></div></body></html>
\ No newline at end of file |