On Wed, Nov 24, 2010 at 7:24 PM, Shane Hathaway <sh...@hathawaymix.org>wrote:
> On 11/24/2010 05:17 AM, Santi Camps wrote: > >> Hi all >> >> I'm using relstorage for a long time with very good results. Until >> know, I also use database adapters like ZPsycopgDA to connect the same >> SQL database and store information in other application tables. I was >> thinking to create a Relstorage Database Adapter able to do the work >> using relstorage configuration and connections. Some preliminary >> simple tests seems to work: >> >> def execute_query(conn, cursor, *args, **kw): >> query = kw['query'] >> cursor.execute(query); >> return cursor >> query = 'SELECT COUNT(*) FROM kmkey_task' >> rows = app._p_jar._storage._with_store(execute_query, query=query) >> print rows.fetchone() >> >> >> The question is, can I go on ? Or use same connections than relstorage >> could cause problems at ZODB level ? >> > > Well, it doesn't look like you're using the two RelStorage connections the > way they are intended to be used. For the code snippet you gave, it's > likely that you want to use the load connection rather than the store > connection. > > The load connection ensures consistent reads. RelStorage does a number of > things to maintain that guarantee. The load connection is never committed, > only rolled back. > > The store connection is intended to be used only during transaction commit. > At the beginning of a commit (tpc_begin), RelStorage rolls back the store > connection in order to get the most recent updates. The store connection > and load connection are often out of sync with each other, so code that uses > the store connection should detect and handle conflicting updates. > > I suspect the load/store connection split is too complicated for most apps > that just want to interact with the database, so I haven't exposed any > documented API. I considered making an API when I worked on > repoze.pgtextindex, but I concluded that pgtextindex can be a bit lazy about > consistency and therefore doesn't need all the extra complexity that reusing > RelStorage connections would bring. > > I understand it. I will try to do it simpler: create new connections using relstorage connection string Thanks a lot for your explanation. -- Santi Camps KMKey hacker (http://www.kmkey.com) Earcon S.L. (http://www.earcon.com)
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