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From Jon Strayer <jstra...@proofpoint.com>
Subject Re: On duplicate key update
Date Tue, 27 Aug 2019 16:05:46 GMT
Just to make sure I understand, anytime an atomic upsert is executed Phoenix translates that
into a checkAndPut.  Is that correct?

From the Atomic Upsert documentation:
"On the server-side, when the commit is processed, the row being updated will be locked while
the current column values are read and the ON DUPLICATE KEY clause is executed."

What I'm not clear on is when the lock happens.  Does it happen every time a upsert with an
"on duplicate key" clause is executed or only after the duplicate key is detected?

Also, if there are two threads attempting to write to the same non-existing row, is there
a race condition where neither thread executes it "on duplicate key" clause? 

On 8/26/19, 7:28 PM, "Josh Elser" <elserj@apache.org> wrote:

    Out of the box, Phoenix will provide the same semantics that HBase does 
    for concurrent updates to a (data) table.
    
    https://urldefense.com/v3/__https://hbase.apache.org/acid-semantics.html__;!YggOdHcy3_sa5w!7XIAKeE5bdWVHeRnJhaMbEwH9vjnhUzpxgoFvOlQBqYoCWp72RMXHdT636yxH4bg3to$

    
    If you're also asking about how index tables remain in sync, the answer 
    is a bit more complicated (and has changed in recent versions).
    
    On 8/26/19 2:51 PM, Jon Strayer wrote:
    > How does atomic update work with multiple clients?  Assuming that there 
    > is no matching record to begin with the access won’t be locked.  It 
    > seems like two threads could write conflicting data since they both see 
    > no existing record (NER).  Is that correct? Or is there something that 
    > will serialize the writes so that only one of them sees the NER state?
    > 
    

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