Sylvain Lebresne created CASSANDRA-4449:
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Summary: Make prepared statement global rather than connection
based
Key: CASSANDRA-4449
URL: https://issues.apache.org/jira/browse/CASSANDRA-4449
Project: Cassandra
Issue Type: Improvement
Reporter: Sylvain Lebresne
Currently, prepared statements are connection based. A client can only use a
prepared statement on the connection it prepared it on, and if you prepare the
same prepared statement on multiple connections, we'll keep multiple times the
same prepared statement. This is potentially inefficient but can also be fairly
painful for client libraries with pool of connections (a.k.a all reasonable
client library ever) as this means you need to make sure you prepare statement
on every connection of the pool, including the connection that don't exist yet
but might be created later.
This ticket suggests making prepared statement global (at least for CQL3), i.e.
move them out of ClientState. This will likely reduce the number of stored
statement on a given node quite a bit, since it's very likely that all clients
to a given node will prepare the same statements (and potentially on all of
their connection with the node). And given that prepared statement identifiers
are the hashCode() of the string, this should be fairly trivial.
I will note that while I think using a hash of the string as identifier is a
very good idea, I don't know if the default java hashCode() is good enough. If
that's a concern, maybe we should use a safer (bug longer) hash like md5 or
sha1. But we'd better do that now.
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