From 8db4109e2b9dd8f5a5a8dac24ba5ce7017feea39 Mon Sep 17 00:00:00 2001
From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Fri, 28 Oct 2005 02:30:01 +0000
Subject: [PATCH]

---
 doc/build/content/pooling.myt | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/doc/build/content/pooling.myt b/doc/build/content/pooling.myt
index ec7a23ca77..823096a825 100644
--- a/doc/build/content/pooling.myt
+++ b/doc/build/content/pooling.myt
@@ -1,5 +1,9 @@
 <%flags>inherit='document_base.myt'</%flags>
 <&|doclib.myt:item, name="pooling", description="Connection Pooling" &>
+    <p>At the base of any database helper library is a system of efficiently acquiring connections to the database.  Since the establishment of a database connection is typically a somewhat expensive operation, an application needs a way to get at database connections repeatedly without incurring the full overhead each time.  Particularly for server-side web applications, a connection pool is the standard way to maintain a "pool" of database connections which are used over and over again among many requests.  Connection pools typcially are configured to maintain a certain "size", which represents how many connections can be used simultaneously without resorting to creating more newly-established connections.
+    </p>
+    <p>SQLAlchemy includes a pooling module that can be used completely independently of the rest of the toolset.  This section describes how it can be used on its own, as well as the available options.  If SQLAlchemy is being used more fully, the connection pooling described below occurs automatically.  The options are still available, though, so this core feature is a good place to start.
+    </p>
     <&|doclib.myt:item, name="establishing", description="Establishing a Transparent Connection Pool" &>
     Any DBAPI module can be "proxied" through the connection pool using the following technique:
     
@@ -22,7 +26,7 @@
     <ul>
         <li>echo=False : if set to True, connections being pulled and retrieved from/to the pool will be logged to the standard output, as well as pool sizing information.</li>
         <li>use_threadlocal=True : if set to True, repeated calls to connect() within the same application thread will be guaranteed to return the <b>same</b> connection object, if one has already been retrieved from the pool and has not been returned yet.  This allows code to retrieve a connection from the pool, and then while still holding on to that connection, to call other functions which also ask the pool for a connection of the same arguments;  those functions will act upon the same connection that the calling method is using.</li>
-        <li>poolclass=QueuePool :  the default class used by the pool module to provide pooling.  QueuePool uses the Python <span class="codeline">Queue.Queue</span> class to maintain a list of available connections.</li>
+        <li>poolclass=QueuePool :  the Pool class used by the pool module to provide pooling.  QueuePool uses the Python <span class="codeline">Queue.Queue</span> class to maintain a list of available connections.  A developer can supply his or her own Pool class to supply a different pooling algorithm.</li>
         <li>pool_size=5 : used by QueuePool - the size of the pool to be maintained.  This is the largest number of connections that will be kept persistently in the pool.  Note that the pool begins with no connections; once this number of connections is requested, that number of connections will remain.</li>
         <li>max_overflow=10 : the maximum overflow size of the pool.  When the number of checked-out connections reaches the size set in pool_size, additional connections will be returned up to this limit.  When those additional connections are returned to the pool, they are disconnected and discarded.  It follows then that the total number of simultaneous connections the pool will allow is pool_size + max_overflow, and the total number of "sleeping" connections the pool will allow is pool_size.  max_overflow can be set to -1 to indicate no overflow limit; no limit will be placed on the total number of concurrent connections.</li>
     </ul>
-- 
2.47.2