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From bastien dine <bastien.d...@gmail.com>
Subject Question about key group / key state & parallelism
Date Wed, 12 Dec 2018 10:21:10 GMT
Hello everyone,

I have a question regarding the key state & parallelism of a process

Doc says : "You can think of Keyed State as Operator State that has been
partitioned, or sharded, with exactly one state-partition per key. Each
keyed-state is logically bound to a unique composite of
<parallel-operator-instance, key>, and since each key “belongs” to exactly
one parallel instance of a keyed operator, we can think of this simply as
<operator, key>."

If I have less parallel operator instance (say 5) than my number of
possible key (10), it means than every instance will "manage" 2 key state ?
(is this spread evenly ?)
Is the logical bound fixed ? I mean, are the state always managed by the
same instance, or does this depends on the available instance at the moment

"During execution each parallel instance of a keyed operator works with the
keys for one or more Key Groups."
-> this is related, does "works with the keys" means always the same keys ?

Best Regards,


Bastien DINE
Data Architect / Software Engineer / Sysadmin

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