[PHOENIX-6] Support ON DUPLICATE KEY construct

• Type: New Feature
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.9.0
• Assignee: James R. Taylor
• Reporter: James R. Taylor
• Created: 20/Jan/14 18:24
• Updated: 07/Nov/16 22:46
• Resolved: 27/Oct/16 21:13

Description

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:

1. This would prevent the setting of VAL to 0 if the row already exists:

   UPSERT INTO T (PK, VAL) VALUES ('a',0) 
   ON DUPLICATE KEY IGNORE;
   

2. This would increment the valueS of COUNTER1 and COUNTER2 if the row already exists and otherwise initialize them to 0:

   UPSERT INTO T (PK, COUNTER1, COUNTER2) VALUES ('a',0,0) 
   ON DUPLICATE KEY UPDATE COUNTER1 = COUNTER1 + 1, COUNTER2 = COUNTER2 + 1;
   

So the general form is:

UPSERT ... VALUES ... [ ON DUPLICATE KEY [IGNORE | UPDATE <column>=<expression>, ...] ]

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.