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Add large object functions catering to SQL callers.

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With these, one need no longer manipulate large object descriptors and
extract numeric constants from header files in order to read and write
large object contents from SQL.

Pavel Stehule, reviewed by Rushabh Lathia.
This commit is contained in:
Noah Misch
2013-10-27 22:42:46 -04:00
parent 9c339eb4f8
commit c50b7c09d8
9 changed files with 362 additions and 7 deletions
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3
doc/src/sgml/func.sgml
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@ -3420,7 +3420,8 @@ SELECT format('Testing %3$s, %2$s, %s', 'one', 'two', 'three');
<para>
See also the aggregate function <function>string_agg</function> in
<xref linkend="functions-aggregate">.
<xref linkend="functions-aggregate"> and the large object functions
in <xref linkend="lo-funcs">.
</para>
</sect1>

78
doc/src/sgml/lobj.sgml
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@ -526,11 +526,79 @@ int lo_unlink(PGconn *conn, Oid lobjId);
<title>Server-side Functions</title>
<para>
There are server-side functions callable from SQL that correspond to
each of the client-side functions described above; indeed, for the
most part the client-side functions are simply interfaces to the
equivalent server-side functions. The ones that are actually useful
to call via SQL commands are
Server-side functions tailored for manipulating large objects from SQL are
listed in <xref linkend="lo-funcs-table">.
</para>
<table id="lo-funcs-table">
<title>SQL-oriented Large Object Functions</title>
<tgroup cols="5">
<thead>
<row>
<entry>Function</entry>
<entry>Return Type</entry>
<entry>Description</entry>
<entry>Example</entry>
<entry>Result</entry>
</row>
</thead>
<tbody>
<row>
<entry>
<indexterm>
<primary>lo_create</primary>
</indexterm>
<literal><function>lo_create(<parameter>loid</parameter> <type>oid</type>, <parameter>string</parameter> <type>bytea</type>)</function></literal>
</entry>
<entry><type>oid</type></entry>
<entry>
Create a large object and store data there, returning its OID.
Pass <literal>0</> to have the system choose an OID.
</entry>
<entry><literal>lo_create(0, E'\\xffffff00')</literal></entry>
<entry><literal>24528</literal></entry>
</row>
<row>
<entry>
<indexterm>
<primary>lo_put</primary>
</indexterm>
<literal><function>lo_put(<parameter>loid</parameter> <type>oid</type>, <parameter>offset</parameter> <type>bigint</type>, <parameter>str</parameter> <type>bytea</type>)</function></literal>
</entry>
<entry><type>void</type></entry>
<entry>
Write data at the given offset.
</entry>
<entry><literal>lo_put(24528, 1, E'\\xaa')</literal></entry>
<entry></entry>
</row>
<row>
<entry>
<indexterm>
<primary>lo_get</primary>
</indexterm>
<literal><function>lo_get(<parameter>loid</parameter> <type>oid</type> <optional>, <parameter>from</parameter> <type>bigint</type>, <parameter>for</parameter> <type>int</type></optional>)</function></literal>
</entry>
<entry><type>bytea</type></entry>
<entry>
Extract contents or a substring thereof.
</entry>
<entry><literal>lo_get(24528, 0, 3)</literal></entry>
<entry><literal>\xffaaff</literal></entry>
</row>
</tbody>
</tgroup>
</table>
<para>
There are additional server-side functions corresponding to each of the
client-side functions described earlier; indeed, for the most part the
client-side functions are simply interfaces to the equivalent server-side
functions. The ones just as convenient to call via SQL commands are
<function>lo_creat</function><indexterm><primary>lo_creat</></>,
<function>lo_create</function><indexterm><primary>lo_create</></>,
<function>lo_unlink</function><indexterm><primary>lo_unlink</></>,