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Add lo_truncate() to backend and libpq for large object truncation.

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Kris Jurka
This commit is contained in:
Bruce Momjian
2007-03-03 19:52:47 +00:00
parent 90d76525c5
commit 0763a56501
12 changed files with 372 additions and 26 deletions
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33
doc/src/sgml/lobj.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/lobj.sgml,v 1.44 2007/02/01 19:10:24 momjian Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/lobj.sgml,v 1.45 2007/03/03 19:52:45 momjian Exp $ -->
<chapter id="largeObjects">
<title id="largeObjects-title">Large Objects</title>
@ -301,6 +301,37 @@ int lo_tell(PGconn *conn, int fd);
</para>
</sect2>
<sect2>
<title>Truncating a Large Object</title>
<para>
To truncate a large object to a given length, call
<synopsis>
int lo_truncate(PGcon *conn, int fd, size_t len);
</synopsis>
<indexterm><primary>lo_truncate</></> truncates the large object
descriptor <parameter>fd</> to length <parameter>len</>. The
<parameter>fd</parameter> argument must have been returned by a
previous <function>lo_open</function>. If <parameter>len</> is
greater than the current large object length, the large object
is extended with null bytes ('\0').
</para>
<para>
The file offset is not changed.
</para>
<para>
On success <function>lo_truncate</function> returns
zero. On error, the return value is negative.
</para>
<para>
<function>lo_truncate</> is new as of <productname>PostgreSQL</productname>
8.3; if this function is run against an older server version, it will
fail and return a negative value.
</para>
<sect2>
<title>Closing a Large Object Descriptor</title>