[Sqlalchemy-commits] [1373] sqlalchemy/branches/schema/doc/build/content/unitofwork.txt: dev
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[Sqlalchemy-commits] [1373] sqlalchemy/branches/schema/doc/build/content/unitofwork.txt: dev
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From: <co...@sq...> - 2006-05-02 00:58:15
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head><style type="text/css"><!-- #msg dl { border: 1px #006 solid; background: #369; padding: 6px; color: #fff; } #msg dt { float: left; width: 6em; font-weight: bold; } #msg dt:after { content:':';} #msg dl, #msg dt, #msg ul, #msg li { font-family: verdana,arial,helvetica,sans-serif; font-size: 10pt; } #msg dl a { font-weight: bold} #msg dl a:link { color:#fc3; } #msg dl a:active { color:#ff0; } #msg dl a:visited { color:#cc6; } h3 { font-family: verdana,arial,helvetica,sans-serif; font-size: 10pt; font-weight: bold; } #msg pre { overflow: auto; background: #ffc; border: 1px #fc0 solid; padding: 6px; } #msg ul, pre { overflow: auto; } #patch { width: 100%; } #patch h4 {font-family: verdana,arial,helvetica,sans-serif;font-size:10pt;padding:8px;background:#369;color:#fff;margin:0;} #patch .propset h4, #patch .binary h4 {margin:0;} #patch pre {padding:0;line-height:1.2em;margin:0;} #patch .diff {width:100%;background:#eee;padding: 0 0 10px 0;overflow:auto;} #patch .propset .diff, #patch .binary .diff {padding:10px 0;} #patch span {display:block;padding:0 10px;} #patch .modfile, #patch .addfile, #patch .delfile, #patch .propset, #patch .binary, #patch .copfile {border:1px solid #ccc;margin:10px 0;} #patch ins {background:#dfd;text-decoration:none;display:block;padding:0 10px;} #patch del {background:#fdd;text-decoration:none;display:block;padding:0 10px;} #patch .lines, .info {color:#888;background:#fff;} --></style> <title>[1373] sqlalchemy/branches/schema/doc/build/content/unitofwork.txt: dev</title> </head> <body> <div id="msg"> <dl> <dt>Revision</dt> <dd>1373</dd> <dt>Author</dt> <dd>zzzeek</dd> <dt>Date</dt> <dd>2006-05-01 19:57:49 -0500 (Mon, 01 May 2006)</dd> </dl> <h3>Log Message</h3> <pre>dev</pre> <h3>Modified Paths</h3> <ul> <li><a href="#sqlalchemybranchesschemadocbuildcontentunitofworktxt">sqlalchemy/branches/schema/doc/build/content/unitofwork.txt</a></li> </ul> </div> <div id="patch"> <h3>Diff</h3> <a id="sqlalchemybranchesschemadocbuildcontentunitofworktxt"></a> <div class="modfile"><h4>Modified: sqlalchemy/branches/schema/doc/build/content/unitofwork.txt (1372 => 1373)</h4> <pre class="diff"><span> <span class="info">--- sqlalchemy/branches/schema/doc/build/content/unitofwork.txt 2006-05-02 00:18:31 UTC (rev 1372) +++ sqlalchemy/branches/schema/doc/build/content/unitofwork.txt 2006-05-02 00:57:49 UTC (rev 1373) </span><span class="lines">@@ -317,10 +317,45 @@ </span><span class="cx"> trans.rollback() </span><span class="cx"> raise </span><span class="cx"> </span><del>-The `create_transaction()` method creates a new SessionTransaction object but does not declare any connection/transaction resources. At the point of the first `get()` call, a connection resource is opened off the engine that corresponds to the Item classes' mapper and is stored within the SessionTransaction with an open Transaction. When `trans.commit()` is called, the `flush()` method is called on the `Session` and the corresponding update statements are issued to the database within the scope of the transaction already opened; afterwards, the underying Transaction is committed, and connection resources are freed. </del><ins>+The `create_transaction()` method creates a new SessionTransaction object but does not declare any connection/transaction resources. At the point of the first `get()` call, a connection resource is opened off the engine that corresponds to the Item classes' mapper and is stored within the `SessionTransaction` with an open `Transaction`. When `trans.commit()` is called, the `flush()` method is called on the `Session` and the corresponding update statements are issued to the database within the scope of the transaction already opened; afterwards, the underying Transaction is committed, and connection resources are freed. </ins><span class="cx"> </span><span class="cx"> `SessionTransaction`, like the `Transaction` off of `Connection` also supports "nested" behavior, and is safe to pass to other functions which then issue their own `begin()`/`commit()` pair; only the outermost `begin()`/`commit()` pair actually affects the transaction, and any call to `rollback()` within a particular call stack will issue a rollback. </span><span class="cx"> </span><ins>+#### Using SQL with SessionTransaction {@name=sql} + +The SessionTransaction can interact with direct SQL queries in two general ways. Either specific `Connection` objects can be associated with the `SessionTransaction`, which are then useable both for direct SQL as well as within `flush()` operations performed by the `SessionTransaction`, or via accessing the `Connection` object automatically referenced within the `SessionTransaction`. + +To associate a specific `Connection` with the `SessionTransaction`, use the `add()` method: + + {python title="Associate a Connection with the SessionTransaction"} + connection = engine.connect() + trans = session.create_transaction() + try: + trans.add(connection) + connection.execute(mytable.update(), {'col1':4, 'col2':17}) + session.flush() # flush() operation will use the same connection + trans.commit() + except: + trans.rollback() + raise + +The `add()` method will key the `Connection`'s underlying `Engine` to this `SessionTransaction`. When mapper operations are performed against this `Engine`, the `Connection` explicitly added will be used. This **overrides** any other `Connection` objects that the Session was associated with, corresponding to the underlying `Engine` of that `Connection`. + +The other way is just to use the `Connection` referenced by the `SessionTransaction`. This is performed via the `connection()` method, and requires passing in a `Mapper` which indicates which underlying `Connection` should be returned. If the `Mapper` argument is `None`, then the `Session` must be globally bound to a specific `Engine` when it was constructed, else the method returns `None`. + + {python title="Get a Connection from the SessionTransaction"} + trans = session.create_transaction() + try: + usermapper = session.get_mapper(UserClass) # a convenience method to get a Mapper + connection = trans.connection(usermapper) # get the Connection used by the UserClass' Mapper + connection.execute(mytable.update(), {'col1':4, 'col2':17}) + trans.commit() + except: + trans.rollback() + raise + +The `connection()` method also exists on the `Session` object itself, and can be called regardless of whether or not a `SessionTransaction` is in progress. If an `Engine` is being used with `threadlocal` strategy, the `Connection` returned will correspond to the connection resources that are bound to the current thread, if any. + </ins><span class="cx"> ### Analyzing Object Flushes {@name=logging} </span><span class="cx"> </span><span class="cx"> The session module can log an extensive display of its "flush plans", which is a graph of its internal representation of objects before they are written to the database. To turn this logging on: </span></span></pre> </div> </div> </body> </html> |