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Document ways to avoid libpq WSACleanup() overhead on Windows. 

Andrew Chernow
This commit is contained in:
Bruce Momjian 2009-02-06 18:18:54 +00:00
parent 8c78f8e65c
commit 3d1a1eeddb
1 changed files with 16 additions and 1 deletions
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17
doc/src/sgml/libpq.sgml
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<!-- $PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.275 2009/01/10 20:14:30 momjian Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.276 2009/02/06 18:18:54 momjian Exp $ -->
<chapter id="libpq">
<title><application>libpq</application> - C Library</title>
@ -63,6 +63,21 @@
The <function>PQstatus</> function should be called to check
whether a connection was successfully made before queries are sent
via the connection object.
<note>
<para>
On Windows, there is a way to improve performance if a single
database connection is repeated started and shutdown. Internally,
libpq calls WSAStartup() and WSACleanup() for connection startup
and shutdown, respectively. WSAStartup() increments an internal
Windows library reference count which is decremented by WSACleanup().
When the reference count is just one, calling WSACleanup() frees
all resources and all DLLs are unloaded. This is an expensive
operation. To avoid this, an application can manually call
WSAStartup() so resources will not be freed when the last database
connection is closed.
</para>
</note>
<variablelist>
<varlistentry>