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https://issues.apache.org/jira/browse/PHOENIX-2909?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15435860#comment-15435860
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Cameron Hatfield commented on PHOENIX-2909:
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I would agree, and I would say is a good argument for having something else
within the merge statement call out the use of whether this will be a fast /
slow version. My basic worry is that when I see something like UPDATE vs UPSERT
or INSERT vs INSERT ... ON DUPLICATE KEY IGNORE, I always expect the more
complicated / does more for me statement to be either the same speed or slower
in the general case. With the proposed change, the more constrained case UPDATE
is actually slower. Whether that is a valid concern is up to debate.
How does this update statement interact with transaction support?
> Surface checkAndPut through UPDATE statement
> --------------------------------------------
>
> Key: PHOENIX-2909
> URL: https://issues.apache.org/jira/browse/PHOENIX-2909
> Project: Phoenix
> Issue Type: Bug
> Reporter: James Taylor
> Assignee: James Taylor
> Fix For: 4.9.0
>
>
> We can surface atomic checkAndPut like functionality through support of the
> SQL UPSERT statement.
> For example, the following could use do a get under row lock to perform the
> row update atomically
> {code}
> UPDATE my_table SET counter=coalesce(counter,0) + 1
> FROM my_table WHERE pk1 = 1 AND pk2 = 2;
> {code}
> To force prior MVCC transactions to complete (making it serializable as an
> Increment is), we'd have code like this:
> {code}
> mvcc = region.getMVCC();
> mvcc.completeMemstoreInsert(mvcc.beginMemstoreInsert());
> {code}
> By users setting auto commit to true and issuing an UPDATE statement over a
> non transactional table, they'd get a way for row updates to be atomic. This
> would work especially well to support counters.
> An UPDATE statement would simply be translated to an equivalent UPSERT SELECT
> with a flag being passed to the server such that the row lock and read occurs
> when executed. For example, the above statement would become:
> {code}
> UPSERT INTO my_table(pk1,pk2,counter) SELECT pk1, pk2, coalesce(counter,0) +
> 1
> FROM my_table WHERE pk1 = 1 AND pk2 = 2;
> {code}
> Note that the coalesce call above handles the case where counter is null.
> This could be made prettier with support for the DEFAULT clause at CREATE
> TABLE time (PHOENIX-476).
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