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https://issues.apache.org/jira/browse/PHOENIX-6?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15612838#comment-15612838
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James Taylor commented on PHOENIX-6:
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bq. How about a couple more test cases where the expression to be evaluated is
a bit more complex like a CASE statement
Sure, I'll the test case with a CASE statement. The complexity of the
expression doesn't make a lot of difference as it's going through the same
ExpressionCompiler that everything goes through.
bq. Also, some test cases around indexes with covered columns where the
expression is updating covered and/or indexed columns.
This is already covered as the test is parameterized with indexes added for
both the indexed and covered column case.
bq. Can you tell me more about the reasoning behind why we disallow the columns
that are part of the row key in the UPDATE clause.
If you update the row key, your inserting a new row that'll potentially land in
a different region on a different region server. We can't support an atomic
operation for that.
We'll document that it's not a great idea to atomically update columns that are
contained in global indexes, but it will work. The preIncrementAfterRowLock
coprocessor hook has an exclusive lock on the row and while under lock the
coprocessors will fire that update the index rows so they'd be updated
atomically as well.
> Support ON DUPLICATE KEY construct
> ----------------------------------
>
> Key: PHOENIX-6
> URL: https://issues.apache.org/jira/browse/PHOENIX-6
> Project: Phoenix
> Issue Type: New Feature
> Reporter: James Taylor
> Assignee: James Taylor
> Fix For: 4.9.0
>
> Attachments: PHOENIX-6.patch, PHOENIX-6_4.x-HBase-0.98.patch,
> PHOENIX-6_v2.patch, PHOENIX-6_v3.patch, PHOENIX-6_wip1.patch,
> PHOENIX-6_wip2.patch, PHOENIX-6_wip3.patch, PHOENIX-6_wip4.patch
>
>
> To support inserting a new row only if it doesn't already exist, we should
> support the "on duplicate key" construct for UPSERT. With this construct, the
> UPSERT VALUES statement would run atomically and would thus require a read
> before write which would obviously have a negative impact on performance. For
> an example of similar syntax , see MySQL documentation at
> http://dev.mysql.com/doc/refman/5.7/en/insert-on-duplicate.html
> See this discussion for more detail:
> https://groups.google.com/d/msg/phoenix-hbase-user/Bof-TLrbTGg/68bnc8ZcWe0J.
> A related discussion is on PHOENIX-2909.
> Initially we'd support the following:
> # This would prevent the setting of VAL to 0 if the row already exists:
> {code}
> UPSERT INTO T (PK, VAL) VALUES ('a',0)
> ON DUPLICATE KEY IGNORE;
> {code}
> # This would increment the valueS of COUNTER1 and COUNTER2 if the row already
> exists and otherwise initialize them to 0:
> {code}
> UPSERT INTO T (PK, COUNTER1, COUNTER2) VALUES ('a',0,0)
> ON DUPLICATE KEY UPDATE COUNTER1 = COUNTER1 + 1, COUNTER2 = COUNTER2 + 1;
> {code}
> So the general form is:
> {code}
> UPSERT ... VALUES ... [ ON DUPLICATE KEY [IGNORE | UPDATE
> <column>=<expression>, ...] ]
> {code}
> The following restrictions will apply:
> * The <column> may not be part of the primary key constraint - only KeyValue
> columns will be allowed.
> * This new clause cannot be used with
> ** Immutable tables since the whole point is to atomically update a row in
> place which isn't allowed for immutable tables.
> ** Transactional tables because these use optimistic concurrency as their
> mechanism for consistency and isolation.
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