Right, which happens to be my situation: many concurrent reads from
different threads, and when a write needs to be done, we lock globally.
Thanks for the (extended) clarification :-)
- Chas
On Oct 22, 2009, at 10:41 AM, Alex Boisvert wrote:
No, that's not safe at all.... unless all the access is read-only.
alex
On Thu, Oct 22, 2009 at 7:36 AM, Chas Emerick
<[email protected]> wrote:
Alex,
Thank you for the clarification. Just to make sure we're
understanding each other, I'm actually asking about multiple
readers, each opening and using their own RecordManagers. Your
mention of synchronization leads me to think you're talking about
multiple threads reading from a single RecordManager.
Just FYI, I'm being careful here because I came across a mention of
RM changing files on disk when *reading*, which surprised me (can't
find the link right now)...
Thanks again,
- Chas
On Oct 22, 2009, at 10:27 AM, Alex Boisvert wrote:
Individual concurrent reads are safe. Pretty much everything is
synchronized at the top of level.
However, iterators / tuple browsers are unsafe under concurrent
updates. You would have to synchronize on the RecordManager
instance to maintain a consistent view while iterating.
alex
On Thu, Oct 22, 2009 at 5:10 AM, Chas Emerick
<[email protected]> wrote:
I've been plumbing around the list archives for a while, but they're
something of a jumble (thanks, Sourceforge!), so I figured I'd open a
new thread to ask:
What level of read concurrency does jdbm support?
What seems clear is that, to be safe, there should only be one thread
writing to a jdbm database (although it appears that it is possible
for multiple threads to participate in a transaction, I'm perfectly
fine with serializing all write access). However, I came across at
least a number of comments that lead me to believe that concurrent
reads are unsafe as well, although they're all from pre-history (e.g.
2001).
Thanks,
- Chas
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