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<div class="document" id="pygresql-programming-information">
<h1 class="title">PyGreSQL Programming Information</h1>
<h2 class="subtitle" id="the-classic-pygresql-interface-pg-module">The classic PyGreSQL interface (pg module)</h2>
<div class="contents topic" id="contents">
<p class="topic-title first"><a name="contents">Contents</a></p>
<ul class="auto-toc simple">
<li><a class="reference" href="#introduction" id="id5" name="id5">1 Introduction</a></li>
<li><a class="reference" href="#module-functions-and-constants" id="id6" name="id6">2 Module functions and constants</a><ul class="auto-toc">
<li><a class="reference" href="#connect-opens-a-pg-connection" id="id7" name="id7">2.1 connect - opens a pg connection</a></li>
<li><a class="reference" href="#get-defhost-set-defhost-default-server-host-dv" id="id8" name="id8">2.2 get_defhost, set_defhost - default server host [DV]</a></li>
<li><a class="reference" href="#get-defport-set-defport-default-server-port-dv" id="id9" name="id9">2.3 get_defport, set_defport - default server port [DV]</a></li>
<li><a class="reference" href="#get-defopt-set-defopt-default-connection-options-dv" id="id10" name="id10">2.4 get_defopt, set_defopt - default connection options [DV]</a></li>
<li><a class="reference" href="#get-deftty-set-deftty-default-debug-tty-dv" id="id11" name="id11">2.5 get_deftty, set_deftty - default debug tty [DV]</a></li>
<li><a class="reference" href="#get-defbase-set-defbase-default-database-name-dv" id="id12" name="id12">2.6 get_defbase, set_defbase - default database name [DV]</a></li>
<li><a class="reference" href="#escape-string-escape-a-string-for-use-within-sql" id="id13" name="id13">2.7 escape_string - escape a string for use within SQL</a></li>
<li><a class="reference" href="#escape-bytea-escape-binary-data-for-use-within-sql-as-type-bytea" id="id14" name="id14">2.8 escape_bytea - escape binary data for use within SQL as type <cite>bytea</cite></a></li>
<li><a class="reference" href="#unescape-bytea-unescape-bytea-data-that-has-been-retrieved-as-text" id="id15" name="id15">2.9 unescape_bytea -- unescape <cite>bytea</cite> data that has been retrieved as text</a></li>
<li><a class="reference" href="#module-constants" id="id16" name="id16">2.10 Module constants</a></li>
</ul>
</li>
<li><a class="reference" href="#connection-objects-pgobject" id="id17" name="id17">3 Connection objects: pgobject</a><ul class="auto-toc">
<li><a class="reference" href="#query-executes-a-sql-command-string" id="id18" name="id18">3.1 query - executes a SQL command string</a></li>
<li><a class="reference" href="#reset-resets-the-connection" id="id19" name="id19">3.2 reset - resets the connection</a></li>
<li><a class="reference" href="#cancel-abandon-processing-of-current-sql-command" id="id20" name="id20">3.3 cancel - abandon processing of current SQL command</a></li>
<li><a class="reference" href="#close-close-the-database-connection" id="id21" name="id21">3.4 close - close the database connection</a></li>
<li><a class="reference" href="#fileno-returns-the-socket-used-to-connect-to-the-database" id="id22" name="id22">3.5 fileno - returns the socket used to connect to the database</a></li>
<li><a class="reference" href="#getnotify-gets-the-last-notify-from-the-server" id="id23" name="id23">3.6 getnotify - gets the last notify from the server</a></li>
<li><a class="reference" href="#inserttable-insert-a-list-into-a-table" id="id24" name="id24">3.7 inserttable - insert a list into a table</a></li>
<li><a class="reference" href="#putline-writes-a-line-to-the-server-socket-da" id="id25" name="id25">3.8 putline - writes a line to the server socket [DA]</a></li>
<li><a class="reference" href="#getline-gets-a-line-from-server-socket-da" id="id26" name="id26">3.9 getline - gets a line from server socket [DA]</a></li>
<li><a class="reference" href="#endcopy-synchronizes-client-and-server-da" id="id27" name="id27">3.10 endcopy - synchronizes client and server [DA]</a></li>
<li><a class="reference" href="#locreate-create-a-large-object-in-the-database-lo" id="id28" name="id28">3.11 locreate - create a large object in the database [LO]</a></li>
<li><a class="reference" href="#getlo-build-a-large-object-from-given-oid-lo" id="id29" name="id29">3.12 getlo - build a large object from given oid [LO]</a></li>
<li><a class="reference" href="#loimport-import-a-file-to-a-large-object-lo" id="id30" name="id30">3.13 loimport - import a file to a large object [LO]</a></li>
<li><a class="reference" href="#object-attributes" id="id31" name="id31">3.14 Object attributes</a></li>
</ul>
</li>
<li><a class="reference" href="#the-db-wrapper-class" id="id32" name="id32">4 The DB wrapper class</a><ul class="auto-toc">
<li><a class="reference" href="#initialization" id="id33" name="id33">4.1 Initialization</a></li>
<li><a class="reference" href="#pkey-return-the-primary-key-of-a-table" id="id34" name="id34">4.2 pkey - return the primary key of a table</a></li>
<li><a class="reference" href="#get-databases-get-list-of-databases-in-the-system" id="id35" name="id35">4.3 get_databases - get list of databases in the system</a></li>
<li><a class="reference" href="#get-relations-get-list-of-relations-in-connected-database" id="id36" name="id36">4.4 get_relations - get list of relations in connected database</a></li>
<li><a class="reference" href="#get-tables-get-list-of-tables-in-connected-database" id="id37" name="id37">4.5 get_tables - get list of tables in connected database</a></li>
<li><a class="reference" href="#get-attnames-get-the-attribute-names-of-a-table" id="id38" name="id38">4.6 get_attnames - get the attribute names of a table</a></li>
<li><a class="reference" href="#get-get-a-row-from-a-database-table-or-view" id="id39" name="id39">4.7 get - get a row from a database table or view</a></li>
<li><a class="reference" href="#insert-insert-a-row-into-a-database-table" id="id40" name="id40">4.8 insert - insert a row into a database table</a></li>
<li><a class="reference" href="#update-update-a-row-in-a-database-table" id="id41" name="id41">4.9 update - update a row in a database table</a></li>
<li><a class="reference" href="#clear-clears-row-values-in-memory" id="id42" name="id42">4.10 clear - clears row values in memory</a></li>
<li><a class="reference" href="#delete-delete-a-row-from-a-database-table" id="id43" name="id43">4.11 delete - delete a row from a database table</a></li>
<li><a class="reference" href="#id1" id="id44" name="id44">4.12 escape_string - escape a string for use within SQL</a></li>
<li><a class="reference" href="#id2" id="id45" name="id45">4.13 escape_bytea - escape binary data for use within SQL as type <cite>bytea</cite></a></li>
<li><a class="reference" href="#id3" id="id46" name="id46">4.14 unescape_bytea -- unescape <cite>bytea</cite> data that has been retrieved as text</a></li>
</ul>
</li>
<li><a class="reference" href="#pgqueryobject-methods" id="id47" name="id47">5 pgqueryobject methods</a><ul class="auto-toc">
<li><a class="reference" href="#getresult-get-query-values-as-list-of-tuples" id="id48" name="id48">5.1 getresult - get query values as list of tuples</a></li>
<li><a class="reference" href="#dictresult-get-query-values-as-list-of-dictionaries" id="id49" name="id49">5.2 dictresult - get query values as list of dictionaries</a></li>
<li><a class="reference" href="#listfields-lists-fields-names-of-previous-query-result" id="id50" name="id50">5.3 listfields - lists fields names of previous query result</a></li>
<li><a class="reference" href="#fieldname-fieldnum-field-name-number-conversion" id="id51" name="id51">5.4 fieldname, fieldnum - field name/number conversion</a></li>
<li><a class="reference" href="#ntuples-return-number-of-tuples-in-query-object" id="id52" name="id52">5.5 ntuples - return number of tuples in query object</a></li>
</ul>
</li>
<li><a class="reference" href="#large-objects-pglarge" id="id53" name="id53">6 Large objects: pglarge</a><ul class="auto-toc">
<li><a class="reference" href="#open-opens-a-large-object" id="id54" name="id54">6.1 open - opens a large object</a></li>
<li><a class="reference" href="#close-closes-a-large-object" id="id55" name="id55">6.2 close - closes a large object</a></li>
<li><a class="reference" href="#read-write-tell-seek-unlink-file-like-large-object-handling" id="id56" name="id56">6.3 read, write, tell, seek, unlink - file like large object handling</a></li>
<li><a class="reference" href="#size-gives-the-large-object-size" id="id57" name="id57">6.4 size - gives the large object size</a></li>
<li><a class="reference" href="#export-saves-a-large-object-to-a-file" id="id58" name="id58">6.5 export - saves a large object to a file</a></li>
<li><a class="reference" href="#id4" id="id59" name="id59">6.6 Object attributes</a></li>
</ul>
</li>
</ul>
</div>
<div class="section" id="introduction">
<h1><a class="toc-backref" href="#id5" name="introduction">1 Introduction</a></h1>
<p>You may either choose to use the
<a class="reference" href="pg.html">"classic" PyGreSQL interface</a>
provided by the <cite>pg</cite> module or else the
<a class="reference" href="pgdb.html">DB-API 2.0 compliant interface</a>
provided by the <cite>pgdb</cite> module.</p>
<p>The following documentation covers only the older <cite>pg</cite> API.</p>
<p>The <cite>pg</cite> module handles three types of objects,</p>
<ul class="simple">
<li>the <cite>pgobject</cite>, which handles the connection
and all the requests to the database,</li>
<li>the <cite>pglarge</cite> object, which handles
all the accesses to PostgreSQL large objects,</li>
<li>the <cite>pgqueryobject</cite> that handles query results</li>
</ul>
<p>and it provides a convenient wrapper class <cite>DB</cite> for the <cite>pgobject</cite>.</p>
<p>If you want to see a simple example of the use of some of these functions,
see <a class="reference" href="http://ontario.bikerides.ca">http://ontario.bikerides.ca</a> where you can find a link at the bottom to the
actual Python code for the page.</p>
</div>
<div class="section" id="module-functions-and-constants">
<h1><a class="toc-backref" href="#id6" name="module-functions-and-constants">2 Module functions and constants</a></h1>
<p>The <cite>pg</cite> module defines a few functions that allow to connect
to a database and to define "default variables" that override
the environment variables used by PostgreSQL.</p>
<p>These "default variables" were designed to allow you to handle general
connection parameters without heavy code in your programs. You can prompt the
user for a value, put it in the default variable, and forget it, without
having to modify your environment. The support for default variables can be
disabled by setting the -DNO_DEF_VAR option in the Python setup file. Methods
relative to this are specified by the tag [DV].</p>
<p>All variables are set to <cite>None</cite> at module initialization, specifying that
standard environment variables should be used.</p>
<div class="section" id="connect-opens-a-pg-connection">
<h2><a class="toc-backref" href="#id7" name="connect-opens-a-pg-connection">2.1 connect - opens a pg connection</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
connect([dbname], [host], [port], [opt], [tty], [user], [passwd])
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">dbname:</th><td class="field-body">name of connected database (string/None)</td>
</tr>
<tr class="field"><th class="field-name">host:</th><td class="field-body">name of the server host (string/None)</td>
</tr>
<tr class="field"><th class="field-name">port:</th><td class="field-body">port used by the database server (integer/-1)</td>
</tr>
<tr class="field"><th class="field-name">opt:</th><td class="field-body">connection options (string/None)</td>
</tr>
<tr class="field"><th class="field-name">tty:</th><td class="field-body">debug terminal (string/None)</td>
</tr>
<tr class="field"><th class="field-name">user:</th><td class="field-body">PostgreSQL user (string/None)</td>
</tr>
<tr class="field"><th class="field-name">passwd:</th><td class="field-body">password for user (string/None)</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">pgobject:</th><td class="field-body">If successful, the <cite>pgobject</cite> handling the connection</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">bad argument type, or too many arguments</td>
</tr>
<tr class="field"><th class="field-name">SyntaxError:</th><td class="field-body">duplicate argument definition</td>
</tr>
<tr class="field"><th class="field-name" colspan="2">pg.InternalError:</th></tr>
<tr><td> </td><td class="field-body">some error occurred during pg connection definition</td>
</tr>
</tbody>
</table>
<p class="last">(plus all exceptions relative to object allocation)</p>
</dd>
<dt>Description:</dt>
<dd>This function opens a connection to a specified database on a given
PostgreSQL server. You can use keywords here, as described in the
Python tutorial. The names of the keywords are the name of the
parameters given in the syntax line. For a precise description
of the parameters, please refer to the PostgreSQL user manual.</dd>
</dl>
<p>Examples:</p>
<pre class="literal-block">
import pg
con1 = pg.connect('testdb', 'myhost', 5432, None, None, 'bob', None)
con2 = pg.connect(dbname='testdb', host='localhost', user='bob')
</pre>
</div>
<div class="section" id="get-defhost-set-defhost-default-server-host-dv">
<h2><a class="toc-backref" href="#id8" name="get-defhost-set-defhost-default-server-host-dv">2.2 get_defhost, set_defhost - default server host [DV]</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
get_defhost()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">string, None:</th><td class="field-body">default host specification</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">too many arguments</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method returns the current default host specification,
or <cite>None</cite> if the environment variables should be used.
Environment variables won't be looked up.</dd>
</dl>
<p>Syntax:</p>
<pre class="literal-block">
set_defhost(host)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">host:</th><td class="field-body">new default host (string/None)</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">string, None:</th><td class="field-body">previous default host specification</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">bad argument type, or too many arguments</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This methods sets the default host value for new connections.
If <cite>None</cite> is supplied as parameter, environment variables will
be used in future connections. It returns the previous setting
for default host.</dd>
</dl>
</div>
<div class="section" id="get-defport-set-defport-default-server-port-dv">
<h2><a class="toc-backref" href="#id9" name="get-defport-set-defport-default-server-port-dv">2.3 get_defport, set_defport - default server port [DV]</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
get_defport()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">integer, None:</th><td class="field-body">default port specification</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">too many arguments</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method returns the current default port specification,
or <cite>None</cite> if the environment variables should be used.
Environment variables won't be looked up.</dd>
</dl>
<p>Syntax:</p>
<pre class="literal-block">
set_defport(port)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">port:</th><td class="field-body">new default port (integer/-1)</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">integer, None:</th><td class="field-body">previous default port specification</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This methods sets the default port value for new connections. If -1 is
supplied as parameter, environment variables will be used in future
connections. It returns the previous setting for default port.</dd>
</dl>
</div>
<div class="section" id="get-defopt-set-defopt-default-connection-options-dv">
<h2><a class="toc-backref" href="#id10" name="get-defopt-set-defopt-default-connection-options-dv">2.4 get_defopt, set_defopt - default connection options [DV]</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
get_defopt()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">string, None:</th><td class="field-body">default options specification</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">too many arguments</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method returns the current default connection options specification,
or <cite>None</cite> if the environment variables should be used. Environment variables
won't be looked up.</dd>
</dl>
<p>Syntax:</p>
<pre class="literal-block">
set_defopt(options)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">options:</th><td class="field-body">new default connection options (string/None)</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">string, None:</th><td class="field-body">previous default options specification</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">bad argument type, or too many arguments</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This methods sets the default connection options value for new connections.
If <cite>None</cite> is supplied as parameter, environment variables will be used in
future connections. It returns the previous setting for default options.</dd>
</dl>
</div>
<div class="section" id="get-deftty-set-deftty-default-debug-tty-dv">
<h2><a class="toc-backref" href="#id11" name="get-deftty-set-deftty-default-debug-tty-dv">2.5 get_deftty, set_deftty - default debug tty [DV]</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
get_deftty()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">string, None:</th><td class="field-body">default debug terminal specification</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">too many arguments</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method returns the current default debug terminal specification, or
<cite>None</cite> if the environment variables should be used. Environment variables
won't be looked up.</dd>
</dl>
<p>Syntax:</p>
<pre class="literal-block">
set_deftty(terminal)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">terminal:</th><td class="field-body">new default debug terminal (string/None)</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">string, None:</th><td class="field-body">previous default debug terminal specification</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">bad argument type, or too many arguments</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This methods sets the default debug terminal value for new connections. If
<cite>None</cite> is supplied as parameter, environment variables will be used in future
connections. It returns the previous setting for default terminal.</dd>
</dl>
</div>
<div class="section" id="get-defbase-set-defbase-default-database-name-dv">
<h2><a class="toc-backref" href="#id12" name="get-defbase-set-defbase-default-database-name-dv">2.6 get_defbase, set_defbase - default database name [DV]</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
get_defbase()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">string, None:</th><td class="field-body">default database name specification</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">too many arguments</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method returns the current default database name specification, or
<cite>None</cite> if the environment variables should be used. Environment variables
won't be looked up.</dd>
</dl>
<p>Syntax:</p>
<pre class="literal-block">
set_defbase(base)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">base:</th><td class="field-body">new default base name (string/None)</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">string, None:</th><td class="field-body">previous default database name specification</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">bad argument type, or too many arguments</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method sets the default database name value for new connections. If
<cite>None</cite> is supplied as parameter, environment variables will be used in
future connections. It returns the previous setting for default host.</dd>
</dl>
</div>
<div class="section" id="escape-string-escape-a-string-for-use-within-sql">
<h2><a class="toc-backref" href="#id13" name="escape-string-escape-a-string-for-use-within-sql">2.7 escape_string - escape a string for use within SQL</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
escape_string(string)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">string:</th><td class="field-body">the string that is to be escaped</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">str:</th><td class="field-body">the escaped string</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">bad argument type, or too many arguments</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This function escapes a string for use within an SQL command.
This is useful when inserting data values as literal constants
in SQL commands. Certain characters (such as quotes and backslashes)
must be escaped to prevent them from being interpreted specially
by the SQL parser. <cite>escape_string</cite> performs this operation.</dd>
</dl>
<div class="caution">
<p class="first admonition-title">Caution!</p>
<p class="last">It is especially important to do proper escaping when
handling strings that were received from an untrustworthy source.
Otherwise there is a security risk: you are vulnerable to "SQL injection"
attacks wherein unwanted SQL commands are fed to your database.</p>
</div>
<p>Example:</p>
<pre class="literal-block">
name = raw_input("Name? ")
phone = con.query("select phone from employees"
" where name='%s'" % escape_string(name)).getresult()
</pre>
</div>
<div class="section" id="escape-bytea-escape-binary-data-for-use-within-sql-as-type-bytea">
<h2><a class="toc-backref" href="#id14" name="escape-bytea-escape-binary-data-for-use-within-sql-as-type-bytea">2.8 escape_bytea - escape binary data for use within SQL as type <cite>bytea</cite></a></h2>
<p>Syntax:</p>
<pre class="literal-block">
escape_bytea(datastring)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">datastring:</th><td class="field-body">string containing the binary data that is to be escaped</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">str:</th><td class="field-body">the escaped string</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">bad argument type, or too many arguments</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>Escapes binary data for use within an SQL command with the type <cite>bytea</cite>.
As with <cite>escape_string</cite>, this is only used when inserting data directly
into an SQL command string.</dd>
</dl>
<p>Example:</p>
<pre class="literal-block">
picture = file('garfield.gif', 'rb').read()
con.query("update pictures set img='%s' where name='Garfield'"
% escape_bytea(picture))
</pre>
</div>
<div class="section" id="unescape-bytea-unescape-bytea-data-that-has-been-retrieved-as-text">
<h2><a class="toc-backref" href="#id15" name="unescape-bytea-unescape-bytea-data-that-has-been-retrieved-as-text">2.9 unescape_bytea -- unescape <cite>bytea</cite> data that has been retrieved as text</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
unescape_bytea(string)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">datastring:</th><td class="field-body">the <cite>bytea</cite> data string that has been retrieved as text</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">str:</th><td class="field-body">string containing the binary data</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">bad argument type, or too many arguments</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>Converts an escaped string representation of binary data into binary
data - the reverse of <cite>escape_bytea</cite>. This is needed when retrieving
<cite>bytea</cite> data with the <cite>getresult()</cite> or <cite>dictresult()</cite> method.</dd>
</dl>
<p>Example:</p>
<pre class="literal-block">
picture = unescape_bytea(con.query(
"select img from pictures where name='Garfield'").getresult[0][0])
file('garfield.gif', 'wb').write(picture)
</pre>
</div>
<div class="section" id="module-constants">
<h2><a class="toc-backref" href="#id16" name="module-constants">2.10 Module constants</a></h2>
<p>Some constants are defined in the module dictionary.
They are intended to be used as parameters for methods calls.
You should refer to the libpq description in the PostgreSQL user manual
for more information about them. These constants are:</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name" colspan="2">version, __version__:</th></tr>
<tr><td> </td><td class="field-body">constants that give the current version.</td>
</tr>
<tr class="field"><th class="field-name" colspan="2">INV_READ, INV_WRITE:</th></tr>
<tr><td> </td><td class="field-body">large objects access modes,
used by <cite>(pgobject.)locreate</cite> and <cite>(pglarge.)open</cite></td>
</tr>
<tr class="field"><th class="field-name" colspan="2">SEEK_SET, SEEK_CUR, SEEK_END:</th></tr>
<tr><td> </td><td class="field-body">positional flags,
used by <cite>(pglarge.)seek</cite></td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="section" id="connection-objects-pgobject">
<h1><a class="toc-backref" href="#id17" name="connection-objects-pgobject">3 Connection objects: pgobject</a></h1>
<p>This object handles a connection to a PostgreSQL database. It embeds and
hides all the parameters that define this connection, thus just leaving really
significant parameters in function calls.</p>
<div class="caution">
<p class="first admonition-title">Caution!</p>
<p>Some methods give direct access to the connection socket.
<em>Do not use them unless you really know what you are doing.</em>
If you prefer disabling them,
set the -DNO_DIRECT option in the Python setup file.</p>
<p class="last"><strong>These methods are specified by the tag [DA].</strong></p>
</div>
<div class="note">
<p class="first admonition-title">Note</p>
<p>Some other methods give access to large objects
(refer to PostgreSQL user manual for more information about these).
If you want to forbid access to these from the module,
set the -DNO_LARGE option in the Python setup file.</p>
<p class="last"><strong>These methods are specified by the tag [LO].</strong></p>
</div>
<div class="section" id="query-executes-a-sql-command-string">
<h2><a class="toc-backref" href="#id18" name="query-executes-a-sql-command-string">3.1 query - executes a SQL command string</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
query(command)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">command:</th><td class="field-body">SQL command (string)</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name" colspan="2">pgqueryobject, None:</th></tr>
<tr><td> </td><td class="field-body">result values</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">bad argument type, or too many arguments</td>
</tr>
<tr class="field"><th class="field-name">ValueError:</th><td class="field-body">empty SQL query or lost connection</td>
</tr>
<tr class="field"><th class="field-name" colspan="2">pg.ProgrammingError:</th></tr>
<tr><td> </td><td class="field-body">error in query</td>
</tr>
<tr class="field"><th class="field-name" colspan="2">pg.InternalError':</th></tr>
<tr><td> </td><td class="field-body">error during query processing</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method simply sends a SQL query to the database. If the query is
an insert statement, the return value is the OID of the newly
inserted row. If it is otherwise a query that does not return a result
(i.e., is not a some kind of SELECT statement), it returns <cite>None</cite>.
Otherwise, it returns a <cite>pgqueryobject</cite> that can be accessed via the
<cite>getresult()</cite> or <cite>dictresult()</cite> method or simply printed.</dd>
</dl>
</div>
<div class="section" id="reset-resets-the-connection">
<h2><a class="toc-backref" href="#id19" name="reset-resets-the-connection">3.2 reset - resets the connection</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
reset()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Return type:</dt>
<dd>None</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">too many (any) arguments</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method resets the current database connection.</dd>
</dl>
</div>
<div class="section" id="cancel-abandon-processing-of-current-sql-command">
<h2><a class="toc-backref" href="#id20" name="cancel-abandon-processing-of-current-sql-command">3.3 cancel - abandon processing of current SQL command</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
cancel()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Return type:</dt>
<dd>None</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">too many (any) arguments</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method requests that the server abandon processing
of the current SQL command.</dd>
</dl>
</div>
<div class="section" id="close-close-the-database-connection">
<h2><a class="toc-backref" href="#id21" name="close-close-the-database-connection">3.4 close - close the database connection</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
close()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Return type:</dt>
<dd>None</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">too many (any) arguments</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method closes the database connection. The connection will
be closed in any case when the connection is deleted but this
allows you to explicitly close it. It is mainly here to allow
the DB-SIG API wrapper to implement a close function.</dd>
</dl>
</div>
<div class="section" id="fileno-returns-the-socket-used-to-connect-to-the-database">
<h2><a class="toc-backref" href="#id22" name="fileno-returns-the-socket-used-to-connect-to-the-database">3.5 fileno - returns the socket used to connect to the database</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
fileno()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">too many (any) arguments</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method returns the underlying socket id used to connect
to the database. This is useful for use in select calls, etc.</dd>
</dl>
</div>
<div class="section" id="getnotify-gets-the-last-notify-from-the-server">
<h2><a class="toc-backref" href="#id23" name="getnotify-gets-the-last-notify-from-the-server">3.6 getnotify - gets the last notify from the server</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
getnotify()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">tuple, None:</th><td class="field-body">last notify from server</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">too many parameters</td>
</tr>
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">invalid connection</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This methods try to get a notify from the server (from the SQL statement
NOTIFY). If the server returns no notify, the methods returns None.
Otherwise, it returns a tuple (couple) <cite>(relname, pid)</cite>, where <cite>relname</cite>
is the name of the notify and <cite>pid</cite> the process id of the connection that
triggered the notify. Remember to do a listen query first otherwise
getnotify() will always return <cite>None</cite>.</dd>
</dl>
</div>
<div class="section" id="inserttable-insert-a-list-into-a-table">
<h2><a class="toc-backref" href="#id24" name="inserttable-insert-a-list-into-a-table">3.7 inserttable - insert a list into a table</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
inserttable(table, values)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">table:</th><td class="field-body">the table name (string)</td>
</tr>
<tr class="field"><th class="field-name">values:</th><td class="field-body">list of rows values (list)</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd>None</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">invalid connection, bad argument type, or too many arguments</td>
</tr>
<tr class="field"><th class="field-name">MemoryError:</th><td class="field-body">insert buffer could not be allocated</td>
</tr>
<tr class="field"><th class="field-name">ValueError:</th><td class="field-body">unsupported values</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method allow to <em>quickly</em> insert large blocks of data in a table:
It inserts the whole values list into the given table. Internally, it
uses the COPY command of the PostgreSQL database. The list is a list
of tuples/lists that define the values for each inserted row. The rows
values may contain string, integer, long or double (real) values.</dd>
</dl>
<div class="caution">
<p class="first admonition-title">Caution!</p>
<p class="last"><em>Be very careful</em>:
This method doesn't typecheck the fields according to the table definition;
it just look whether or not it knows how to handle such types.</p>
</div>
</div>
<div class="section" id="putline-writes-a-line-to-the-server-socket-da">
<h2><a class="toc-backref" href="#id25" name="putline-writes-a-line-to-the-server-socket-da">3.8 putline - writes a line to the server socket [DA]</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
putline(line)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">line:</th><td class="field-body">line to be written (string)</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd>None</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">invalid connection, bad parameter type, or too many parameters</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method allows to directly write a string to the server socket.</dd>
</dl>
</div>
<div class="section" id="getline-gets-a-line-from-server-socket-da">
<h2><a class="toc-backref" href="#id26" name="getline-gets-a-line-from-server-socket-da">3.9 getline - gets a line from server socket [DA]</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
getline()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">string:</th><td class="field-body">the line read</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">invalid connection</td>
</tr>
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">too many parameters</td>
</tr>
<tr class="field"><th class="field-name">MemoryError:</th><td class="field-body">buffer overflow</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method allows to directly read a string from the server socket.</dd>
</dl>
</div>
<div class="section" id="endcopy-synchronizes-client-and-server-da">
<h2><a class="toc-backref" href="#id27" name="endcopy-synchronizes-client-and-server-da">3.10 endcopy - synchronizes client and server [DA]</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
endcopy()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Return type:</dt>
<dd>None</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">invalid connection</td>
</tr>
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">too many parameters</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>The use of direct access methods may desynchonize client and server.
This method ensure that client and server will be synchronized.</dd>
</dl>
</div>
<div class="section" id="locreate-create-a-large-object-in-the-database-lo">
<h2><a class="toc-backref" href="#id28" name="locreate-create-a-large-object-in-the-database-lo">3.11 locreate - create a large object in the database [LO]</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
locreate(mode)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">mode:</th><td class="field-body">large object create mode</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">pglarge:</th><td class="field-body">object handling the PostGreSQL large object</td>
</tr>
</tbody>
</table>
</dd>
</dl>
<p>Exceptions raised:</p>
<blockquote>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">invalid connection, bad parameter type, or too many parameters</td>
</tr>
<tr class="field"><th class="field-name" colspan="2">pg.OperationalError:</th></tr>
<tr><td> </td><td class="field-body">creation error</td>
</tr>
</tbody>
</table>
</blockquote>
<dl class="docutils">
<dt>Description:</dt>
<dd>This method creates a large object in the database. The mode can be defined
by OR-ing the constants defined in the pg module (INV_READ, INV_WRITE and
INV_ARCHIVE). Please refer to PostgreSQL user manual for a description of
the mode values.</dd>
</dl>
</div>
<div class="section" id="getlo-build-a-large-object-from-given-oid-lo">
<h2><a class="toc-backref" href="#id29" name="getlo-build-a-large-object-from-given-oid-lo">3.12 getlo - build a large object from given oid [LO]</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
getlo(oid)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">oid:</th><td class="field-body">OID of the existing large object (integer)</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">pglarge:</th><td class="field-body">object handling the PostGreSQL large object</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">invalid connection, bad parameter type, or too many parameters</td>
</tr>
<tr class="field"><th class="field-name">ValueError:</th><td class="field-body">bad OID value (0 is invalid_oid)</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method allows to reuse a formerly created large object through the
<cite>pglarge</cite> interface, providing the user have its OID.</dd>
</dl>
</div>
<div class="section" id="loimport-import-a-file-to-a-large-object-lo">
<h2><a class="toc-backref" href="#id30" name="loimport-import-a-file-to-a-large-object-lo">3.13 loimport - import a file to a large object [LO]</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
loimport(name)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">name:</th><td class="field-body">the name of the file to be imported (string)</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">pglarge:</th><td class="field-body">object handling the PostGreSQL large object</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">invalid connection, bad argument type, or too many arguments</td>
</tr>
<tr class="field"><th class="field-name" colspan="2">pg.OperationalError:</th></tr>
<tr><td> </td><td class="field-body">error during file import</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This methods allows to create large objects in a very simple way. You just
give the name of a file containing the data to be use.</dd>
</dl>
</div>
<div class="section" id="object-attributes">
<h2><a class="toc-backref" href="#id31" name="object-attributes">3.14 Object attributes</a></h2>
<p>Every <cite>pgobject</cite> defines a set of read-only attributes that describe the
connection and its status. These attributes are:</p>
<blockquote>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">host:</th><td class="field-body">the host name of the server (string)</td>
</tr>
<tr class="field"><th class="field-name">port:</th><td class="field-body">the port of the server (integer)</td>
</tr>
<tr class="field"><th class="field-name">db:</th><td class="field-body">the selected database (string)</td>
</tr>
<tr class="field"><th class="field-name">options:</th><td class="field-body">the connection options (string)</td>
</tr>
<tr class="field"><th class="field-name">tty:</th><td class="field-body">the connection debug terminal (string)</td>
</tr>
<tr class="field"><th class="field-name">user:</th><td class="field-body">user name on the database system (string)</td>
</tr>
<tr class="field"><th class="field-name">status:</th><td class="field-body">the status of the connection (integer: 1 - OK, 0 - bad)</td>
</tr>
<tr class="field"><th class="field-name">error:</th><td class="field-body">the last warning/error message from the server (string)</td>
</tr>
</tbody>
</table>
</blockquote>
</div>
</div>
<div class="section" id="the-db-wrapper-class">
<h1><a class="toc-backref" href="#id32" name="the-db-wrapper-class">4 The DB wrapper class</a></h1>
<p>The <cite>pgobject</cite> methods are wrapped in the class <cite>DB</cite>.
The preferred way to use this module is as follows:</p>
<pre class="literal-block">
import pg
db = pg.DB(...) # see below
for r in db.query( # just for example
"""SELECT foo,bar
FROM foo_bar_table
WHERE foo !~ bar"""
).dictresult():
print '%(foo)s %(bar)s' % r
</pre>
<p>The following describes the methods and variables of this class.</p>
<div class="section" id="initialization">
<h2><a class="toc-backref" href="#id33" name="initialization">4.1 Initialization</a></h2>
<p>The DB class is initialized with the same arguments as the connect
function described in section 2. It also initializes a few
internal variables. The statement <tt class="docutils literal"><span class="pre">db</span> <span class="pre">=</span> <span class="pre">DB()</span></tt> will open the
local database with the name of the user just like connect() does.</p>
</div>
<div class="section" id="pkey-return-the-primary-key-of-a-table">
<h2><a class="toc-backref" href="#id34" name="pkey-return-the-primary-key-of-a-table">4.2 pkey - return the primary key of a table</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
pkey(table)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">table:</th><td class="field-body">name of table</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">string:</th><td class="field-body">Name of the field which is the primary key of the table</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method returns the primary key of a table. Note that this raises
an exception if the table does not have a primary key.</dd>
</dl>
</div>
<div class="section" id="get-databases-get-list-of-databases-in-the-system">
<h2><a class="toc-backref" href="#id35" name="get-databases-get-list-of-databases-in-the-system">4.3 get_databases - get list of databases in the system</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
get_databases()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">list:</th><td class="field-body">all databases in the system</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>Although you can do this with a simple select, it is added here for
convenience.</dd>
</dl>
</div>
<div class="section" id="get-relations-get-list-of-relations-in-connected-database">
<h2><a class="toc-backref" href="#id36" name="get-relations-get-list-of-relations-in-connected-database">4.4 get_relations - get list of relations in connected database</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
get_relations(kinds)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">kinds:</th><td class="field-body">a string or sequence of type letters</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>The type letters are <cite>r</cite> = ordinary table, <cite>i</cite> = index, <cite>S</cite> = sequence,
<cite>v</cite> = view, <cite>c</cite> = composite type, <cite>s</cite> = special, <cite>t</cite> = TOAST table.
If <cite>kinds</cite> is None or an empty string, all relations are returned (this is
also the default). Although you can do this with a simple select, it is
added here for convenience.</dd>
</dl>
</div>
<div class="section" id="get-tables-get-list-of-tables-in-connected-database">
<h2><a class="toc-backref" href="#id37" name="get-tables-get-list-of-tables-in-connected-database">4.5 get_tables - get list of tables in connected database</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
get_tables()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Returns:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">list:</th><td class="field-body">all tables in connected database</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>Although you can do this with a simple select, it is added here for
convenience.</dd>
</dl>
</div>
<div class="section" id="get-attnames-get-the-attribute-names-of-a-table">
<h2><a class="toc-backref" href="#id38" name="get-attnames-get-the-attribute-names-of-a-table">4.6 get_attnames - get the attribute names of a table</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
get_attnames(table)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">table:</th><td class="field-body">name of table</td>
</tr>
</tbody>
</table>
</dd>
<dt>Returns:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">dictionary:</th><td class="field-body">The keys are the attribute names,
the values are the type names of the attributes.</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>Given the name of a table, digs out the set of attribute names.</dd>
</dl>
</div>
<div class="section" id="get-get-a-row-from-a-database-table-or-view">
<h2><a class="toc-backref" href="#id39" name="get-get-a-row-from-a-database-table-or-view">4.7 get - get a row from a database table or view</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
get(table, arg, [keyname])
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">table:</th><td class="field-body">name of table or view</td>
</tr>
<tr class="field"><th class="field-name">arg:</th><td class="field-body">either a dictionary or the value to be looked up</td>
</tr>
<tr class="field"><th class="field-name">keyname:</th><td class="field-body">name of field to use as key (optional)</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">dictionary:</th><td class="field-body">The keys are the attribute names,
the values are the row values.</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method is the basic mechanism to get a single row. It assumes
that the key specifies a unique row. If keyname is not specified
then the primary key for the table is used. If <cite>arg</cite> is a dictionary
then the value for the key is taken from it and it is modified to
include the new values, replacing existing values where necessary.
The OID is also put into the dictionary, but in order to allow the
caller to work with multiple tables, it is munged as <cite>oid(schema.table)</cite>.</dd>
</dl>
</div>
<div class="section" id="insert-insert-a-row-into-a-database-table">
<h2><a class="toc-backref" href="#id40" name="insert-insert-a-row-into-a-database-table">4.8 insert - insert a row into a database table</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
insert(table, a)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">table:</th><td class="field-body">name of table</td>
</tr>
<tr class="field"><th class="field-name">a:</th><td class="field-body">a dictionary of values</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">integer:</th><td class="field-body">the OID of the newly inserted row</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd><p class="first">This method inserts values into the table specified filling in the
values from the dictionary. It then reloads the dictionary with the
values from the database. This causes the dictionary to be updated
with values that are modified by rules, triggers, etc.</p>
<p class="last">Due to the way that this function works you will find inserts taking
longer and longer as your table gets bigger. To overcome this problem
simply add an index onto the OID of any table that you think may get
large over time. You may also consider using the inserttable() method
described in section 3.</p>
</dd>
</dl>
</div>
<div class="section" id="update-update-a-row-in-a-database-table">
<h2><a class="toc-backref" href="#id41" name="update-update-a-row-in-a-database-table">4.9 update - update a row in a database table</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
update(table, a)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">table:</th><td class="field-body">name of table</td>
</tr>
<tr class="field"><th class="field-name">a:</th><td class="field-body">a dictionary of values</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">dictionary:</th><td class="field-body">the new row</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>Similar to insert but updates an existing row. The update is based
on the OID value as munged by get. The array returned is the
one sent modified to reflect any changes caused by the update due
to triggers, rules, defaults, etc.</dd>
</dl>
</div>
<div class="section" id="clear-clears-row-values-in-memory">
<h2><a class="toc-backref" href="#id42" name="clear-clears-row-values-in-memory">4.10 clear - clears row values in memory</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
clear(table, [a])
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">table:</th><td class="field-body">name of table</td>
</tr>
<tr class="field"><th class="field-name">a:</th><td class="field-body">a dictionary of values</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">dictionary:</th><td class="field-body">an empty row</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method clears all the attributes to values determined by the types.
Numeric types are set to 0, Booleans are set to 'f', dates are set
to 'now()' and everything else is set to the empty string.
If the array argument is present, it is used as the array and any entries
matching attribute names are cleared with everything else left unchanged.</dd>
</dl>
</div>
<div class="section" id="delete-delete-a-row-from-a-database-table">
<h2><a class="toc-backref" href="#id43" name="delete-delete-a-row-from-a-database-table">4.11 delete - delete a row from a database table</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
delete(table, [a])
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">table:</th><td class="field-body">name of table</td>
</tr>
<tr class="field"><th class="field-name">a:</th><td class="field-body">a dictionary of values</td>
</tr>
</tbody>
</table>
</dd>
<dt>Returns:</dt>
<dd>None</dd>
<dt>Description:</dt>
<dd>This method deletes the row from a table. It deletes based on the OID
as munged as described above.</dd>
</dl>
</div>
<div class="section" id="id1">
<h2><a class="toc-backref" href="#id44" name="id1">4.12 escape_string - escape a string for use within SQL</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
escape_string(string)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">string:</th><td class="field-body">the string that is to be escaped</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">str:</th><td class="field-body">the escaped string</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>See the module function with the same name.</dd>
</dl>
</div>
<div class="section" id="id2">
<h2><a class="toc-backref" href="#id45" name="id2">4.13 escape_bytea - escape binary data for use within SQL as type <cite>bytea</cite></a></h2>
<p>Syntax:</p>
<pre class="literal-block">
escape_bytea(datastring)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">datastring:</th><td class="field-body">string containing the binary data that is to be escaped</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">str:</th><td class="field-body">the escaped string</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>See the module function with the same name.</dd>
</dl>
</div>
<div class="section" id="id3">
<h2><a class="toc-backref" href="#id46" name="id3">4.14 unescape_bytea -- unescape <cite>bytea</cite> data that has been retrieved as text</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
unescape_bytea(string)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">datastring:</th><td class="field-body">the <cite>bytea</cite> data string that has been retrieved as text</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">str:</th><td class="field-body">string containing the binary data</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>See the module function with the same name.</dd>
</dl>
</div>
</div>
<div class="section" id="pgqueryobject-methods">
<h1><a class="toc-backref" href="#id47" name="pgqueryobject-methods">5 pgqueryobject methods</a></h1>
<div class="section" id="getresult-get-query-values-as-list-of-tuples">
<h2><a class="toc-backref" href="#id48" name="getresult-get-query-values-as-list-of-tuples">5.1 getresult - get query values as list of tuples</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
getresult()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">list:</th><td class="field-body">result values as a list of tuples</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">too many parameters</td>
</tr>
<tr class="field"><th class="field-name" colspan="2">pg.InternalError:</th></tr>
<tr><td> </td><td class="field-body">invalid previous result</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method returns the list of the values returned by the query.
More information about this result may be accessed using listfields(),
fieldname() and fieldnum() methods.</dd>
</dl>
</div>
<div class="section" id="dictresult-get-query-values-as-list-of-dictionaries">
<h2><a class="toc-backref" href="#id49" name="dictresult-get-query-values-as-list-of-dictionaries">5.2 dictresult - get query values as list of dictionaries</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
dictresult()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">list:</th><td class="field-body">result values as a list of dictionaries</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">too many parameters</td>
</tr>
<tr class="field"><th class="field-name" colspan="2">pg.InternalError:</th></tr>
<tr><td> </td><td class="field-body">invalid previous result</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method returns the list of the values returned by the query
with each tuple returned as a dictionary with the field names
used as the dictionary index.</dd>
</dl>
</div>
<div class="section" id="listfields-lists-fields-names-of-previous-query-result">
<h2><a class="toc-backref" href="#id50" name="listfields-lists-fields-names-of-previous-query-result">5.3 listfields - lists fields names of previous query result</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
listfields()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">list:</th><td class="field-body">field names</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">too many parameters</td>
</tr>
<tr class="field"><th class="field-name" colspan="2">pg.InternalError:</th></tr>
<tr><td> </td><td class="field-body">invalid previous result, or lost connection</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method returns the list of names of the fields defined for the
query result. The fields are in the same order as the result values.</dd>
</dl>
</div>
<div class="section" id="fieldname-fieldnum-field-name-number-conversion">
<h2><a class="toc-backref" href="#id51" name="fieldname-fieldnum-field-name-number-conversion">5.4 fieldname, fieldnum - field name/number conversion</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
fieldname(i)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">i:</th><td class="field-body">field number (integer)</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">string:</th><td class="field-body">field name</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">invalid connection, bad parameter type, or too many parameters</td>
</tr>
<tr class="field"><th class="field-name">ValueError:</th><td class="field-body">invalid field number</td>
</tr>
<tr class="field"><th class="field-name" colspan="2">pg.InternalError:</th></tr>
<tr><td> </td><td class="field-body">invalid previous result, or lost connection</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method allows to find a field name from its rank number. It can be
useful for displaying a result. The fields are in the same order as the
result values.</dd>
</dl>
<p>Syntax:</p>
<pre class="literal-block">
fieldnum(name)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">name:</th><td class="field-body">field name (string)</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">integer:</th><td class="field-body">field number</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">invalid connection, bad parameter type, or too many parameters</td>
</tr>
<tr class="field"><th class="field-name">ValueError:</th><td class="field-body">unknown field name</td>
</tr>
<tr class="field"><th class="field-name" colspan="2">pg.InternalError:</th></tr>
<tr><td> </td><td class="field-body">invalid previous result, or lost connection</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method returns a field number from its name. It can be used to
build a function that converts result list strings to their correct
type, using a hardcoded table definition. The number returned is the
field rank in the result values list.</dd>
</dl>
</div>
<div class="section" id="ntuples-return-number-of-tuples-in-query-object">
<h2><a class="toc-backref" href="#id52" name="ntuples-return-number-of-tuples-in-query-object">5.5 ntuples - return number of tuples in query object</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
ntuples()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">integer:</th><td class="field-body">number of tuples in <cite>pgqueryobject</cite></td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">Too many arguments.</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method returns the number of tuples found in a query.</dd>
</dl>
</div>
</div>
<div class="section" id="large-objects-pglarge">
<h1><a class="toc-backref" href="#id53" name="large-objects-pglarge">6 Large objects: pglarge</a></h1>
<p>This object handles all the request concerning a PostgreSQL large object. It
embeds and hides all the "recurrent" variables (object OID and connection),
exactly in the same way <cite>pgobjects</cite> do, thus only keeping significant
parameters in function calls. It keeps a reference to the <cite>pgobject</cite> used for
its creation, sending requests though with its parameters. Any modification but
dereferencing the <cite>pgobject</cite> will thus affect the <cite>pglarge</cite> object.
Dereferencing the initial <cite>pgobject</cite> is not a problem since Python won't
deallocate it before the <cite>pglarge</cite> object dereference it.
All functions return a generic error message on call error, whatever the
exact error was. The <cite>error</cite> attribute of the object allow to get the exact
error message.</p>
<p>See also the PostgreSQL programmer's guide for more information about the
large object interface.</p>
<div class="section" id="open-opens-a-large-object">
<h2><a class="toc-backref" href="#id54" name="open-opens-a-large-object">6.1 open - opens a large object</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
open(mode)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">mode:</th><td class="field-body">open mode definition (integer)</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd>None</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">invalid connection, bad parameter type, or too many parameters</td>
</tr>
<tr class="field"><th class="field-name">IOError:</th><td class="field-body">already opened object, or open error</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method opens a large object for reading/writing, in the same way than
the Unix open() function. The mode value can be obtained by OR-ing the
constants defined in the pgmodule (INV_READ, INV_WRITE).</dd>
</dl>
</div>
<div class="section" id="close-closes-a-large-object">
<h2><a class="toc-backref" href="#id55" name="close-closes-a-large-object">6.2 close - closes a large object</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
close()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Return type:</dt>
<dd>None</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">invalid connection</td>
</tr>
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">too many parameters</td>
</tr>
<tr class="field"><th class="field-name">IOError:</th><td class="field-body">object is not opened, or close error</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method closes a previously opened large object, in the same way than
the Unix close() function.</dd>
</dl>
</div>
<div class="section" id="read-write-tell-seek-unlink-file-like-large-object-handling">
<h2><a class="toc-backref" href="#id56" name="read-write-tell-seek-unlink-file-like-large-object-handling">6.3 read, write, tell, seek, unlink - file like large object handling</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
read(size)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">size:</th><td class="field-body">maximal size of the buffer to be read</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">sized string:</th><td class="field-body">the read buffer</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">invalid connection, invalid object,
bad parameter type, or too many parameters</td>
</tr>
<tr class="field"><th class="field-name">ValueError:</th><td class="field-body">if <cite>size</cite> is negative</td>
</tr>
<tr class="field"><th class="field-name">IOError:</th><td class="field-body">object is not opened, or read error</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This function allows to read data from a large object, starting at current
position.</dd>
</dl>
<p>Syntax:</p>
<pre class="literal-block">
write(string)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>(sized) string - buffer to be written</dd>
<dt>Return type:</dt>
<dd>None</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">invalid connection, bad parameter type, or too many parameters</td>
</tr>
<tr class="field"><th class="field-name">IOError:</th><td class="field-body">object is not opened, or write error</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This function allows to write data to a large object, starting at current
position.</dd>
</dl>
<p>Syntax:</p>
<pre class="literal-block">
seek(offset, whence)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">offset:</th><td class="field-body">position offset</td>
</tr>
<tr class="field"><th class="field-name">whence:</th><td class="field-body">positional parameter</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">integer:</th><td class="field-body">new position in object</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">binvalid connection or invalid object,
bad parameter type, or too many parameters</td>
</tr>
<tr class="field"><th class="field-name">IOError:</th><td class="field-body">object is not opened, or seek error</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method allows to move the position cursor in the large object. The
whence parameter can be obtained by OR-ing the constants defined in the
<cite>pg</cite> module (<cite>SEEK_SET</cite>, <cite>SEEK_CUR</cite>, <cite>SEEK_END</cite>).</dd>
</dl>
<p>Syntax:</p>
<pre class="literal-block">
tell()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">integer:</th><td class="field-body">current position in large object</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">invalid connection or invalid object</td>
</tr>
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">too many parameters</td>
</tr>
<tr class="field"><th class="field-name">IOError:</th><td class="field-body">object is not opened, or seek error</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This method allows to get the current position in the large object.</dd>
</dl>
<p>Syntax:</p>
<pre class="literal-block">
unlink()
</pre>
<dl class="docutils">
<dt>Parameter:</dt>
<dd>None</dd>
<dt>Return type:</dt>
<dd>None</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">invalid connection or invalid object</td>
</tr>
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">too many parameters</td>
</tr>
<tr class="field"><th class="field-name">IOError:</th><td class="field-body">object is not closed, or unlink error</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This methods unlinks (deletes) the PostgreSQL large object.</dd>
</dl>
</div>
<div class="section" id="size-gives-the-large-object-size">
<h2><a class="toc-backref" href="#id57" name="size-gives-the-large-object-size">6.4 size - gives the large object size</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
size()
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd>None</dd>
<dt>Return type:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">integer:</th><td class="field-body">the large object size</td>
</tr>
</tbody>
</table>
</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">invalid connection or invalid object</td>
</tr>
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">too many parameters</td>
</tr>
<tr class="field"><th class="field-name">IOError:</th><td class="field-body">object is not opened, or seek/tell error</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This (composite) method allows to get the size of a large object. It was
implemented because this function is very useful for a web interfaced
database. Currently, the large object needs to be opened first.</dd>
</dl>
</div>
<div class="section" id="export-saves-a-large-object-to-a-file">
<h2><a class="toc-backref" href="#id58" name="export-saves-a-large-object-to-a-file">6.5 export - saves a large object to a file</a></h2>
<p>Syntax:</p>
<pre class="literal-block">
export(name)
</pre>
<dl class="docutils">
<dt>Parameters:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">name:</th><td class="field-body">file to be created</td>
</tr>
</tbody>
</table>
</dd>
<dt>Return type:</dt>
<dd>None</dd>
<dt>Exceptions raised:</dt>
<dd><table class="first last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">TypeError:</th><td class="field-body">invalid connection or invalid object,
bad parameter type, or too many parameters</td>
</tr>
<tr class="field"><th class="field-name">IOError:</th><td class="field-body">object is not closed, or export error</td>
</tr>
</tbody>
</table>
</dd>
<dt>Description:</dt>
<dd>This methods allows to dump the content of a large object in a very simple
way. The exported file is created on the host of the program, not the
server host.</dd>
</dl>
</div>
<div class="section" id="id4">
<h2><a class="toc-backref" href="#id59" name="id4">6.6 Object attributes</a></h2>
<p><cite>pglarge</cite> objects define a read-only set of attributes that allow to get
some information about it. These attributes are:</p>
<blockquote>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">oid:</th><td class="field-body">the OID associated with the object</td>
</tr>
<tr class="field"><th class="field-name">pgcnx:</th><td class="field-body">the <cite>pgobject</cite> associated with the object</td>
</tr>
<tr class="field"><th class="field-name">error:</th><td class="field-body">the last warning/error message of the connection</td>
</tr>
</tbody>
</table>
</blockquote>
<div class="caution">
<p class="first admonition-title">Caution!</p>
<p class="last"><em>Be careful</em>:
In multithreaded environments, <cite>error</cite> may be modified by another thread
using the same pgobject. Remember these object are shared, not duplicated.
You should provide some locking to be able if you want to check this.
The <cite>oid</cite> attribute is very interesting because it allow you reuse the OID
later, creating the <cite>pglarge</cite> object with a <cite>pgobject</cite> getlo() method call.</p>
</div>
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