On Sep 22, 2014, at 1:40 PM, Milind Vaidya <[email protected]> wrote:
> is it true of sqlalchemy verison 0.7 (which BTW I am using)?
yes.
from sqlalchemy import *
e = create_engine("mysql://scott:tiger@localhost/test", echo=True)
m = MetaData()
t = Table('t', m, Column('x', Integer, primary_key=True), Column('y', Integer))
m.create_all(e)
with e.begin() as conn:
result = conn.execute(t.insert(), x=1, y=2)
assert result.closed
> If I close() explicitly only for insert queries, I can see that parallel
> inserts happening equal to no. of threads that I have, but if I remove it, no
> parallel inserts happen(I am checking this by using show processlist on mysql
> prompt)
there should be nothing whatsoever done in "parallel" relative to a single
connection with the Python DBAPI, and especially with MySQLdb. In your code
snippet, if "self.session" should absolutely never be shared with more than one
thread at a time. Plenty of docs on this at
http://docs.sqlalchemy.org/en/rel_0_9/orm/session.html#is-the-session-thread-safe
> pool_size = 150 : when close() is called.
> pool_size = 30 : when close() in not called.
its hard to tell what would be causing this without example code that can
illustrate the full context. the kind of pattern you have in "def
execute_query()" is one that is usually associated with problems like these,
though, because its hard to have a single logical operation in your program
refer to multiple, ad-hoc transactions/connections that are each established
every time execute_query() is called. the preferred system is one that
establishes a new session at the start of an entire operation at the use-case
level (like, a web request starts), makes that single session available
throughout the scope of an operation, then when the use-case is fully complete
the session is closed. the pattern here is turning that inside out.
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