Thank you so much, knowing this, I assume that I have some debugging ahead, thank you again.
On 3/21/15, Michael Bayer <mike...@zzzcomputing.com> wrote: > > > dcgh...@gmail.com wrote: > >> Hello there, >> >> I have the following code structure (more or less) in several processes: >> >> from sqlalchemy import create_engine >> from sqlalchemy.orm import sessionmaker >> >> engine = create_engine(some_mysql_dburi) >> session = sessionmaker(bind=engine)() >> >> while True: >> query = session.query(...).filter(...) >> # do something here from that query, update, insert new rows, etc. >> session.commit() >> >> I am getting a too many connections error and it's not all the time, so >> I'm not sure what would it be. Although there are several processes >> running, I don't think at some time I'm connected to mysql server more >> than the amount of connections allowed, which by default it's about 150 >> connections I think, and I'm not modifying the default value. So I must >> have some errors in this layout of my code. Here are some of the questions >> about the session and the connection(s) within I'd like to ask: >> 1- How many opened connections are maintained by a single session object? >> I read somewhere it's only one, but, here it's my next > > if only one engine is associated with it, them just one connection. > >> 2- Does the session close the connection being used or requests for >> another? > > assuming the session isn’t in “autocommit” mode, the connection stays open > until you call commit(), rollback(), or close(). > >> If it requests for a new one, does it close the previous (i.e., return it >> to the engine pool)? > > just one connection at a time yup > >> 3- Should I call session.close() right after the session.commit() >> statement? > > it’s not necessary, however all objects that are associated with that > session are still able to make it start up a new transaction if you keep > using those objects and hit upon unloaded attributes. close() would prevent > that. > >> If have to, do I have to put the session creation inside the while? > > not the way it is above; after that commit(), the Session there isn’t > connected to anything. Unless the objects associated with it are being used > in other threads, or something like that. > >> I read that when the session gets garbage collected the connection(s) >> is(are) closed, > > that happens also but the commit() is enough (and close() makes it sure). > >> so I could do this, but I don't know if it is a good use of the session. >> >> I read the docs many times and I didn't find anything solid that answers >> that questions to me, any help on the subject will be very appreciated, >> thanks in advance. > > the best section is this one: > http://docs.sqlalchemy.org/en/rel_0_9/orm/session_basics.html#when-do-i-construct-a-session-when-do-i-commit-it-and-when-do-i-close-it. > >> -- >> You received this message because you are subscribed to the Google Groups >> "sqlalchemy" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to sqlalchemy+unsubscr...@googlegroups.com. >> To post to this group, send email to sqlalchemy@googlegroups.com. >> Visit this group at http://groups.google.com/group/sqlalchemy. >> For more options, visit https://groups.google.com/d/optout. > > -- > You received this message because you are subscribed to a topic in the > Google Groups "sqlalchemy" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/sqlalchemy/kD7hl_jkCQI/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > sqlalchemy+unsubscr...@googlegroups.com. > To post to this group, send email to sqlalchemy@googlegroups.com. > Visit this group at http://groups.google.com/group/sqlalchemy. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
