tree 0af2840d5008403f44627cb9f43e9db4987401f0
parent 029dd2f8f01952c0166a43fd4e4839ce172eaf6b
author Shawn O. Pearce <sop@google.com> 1262287729 -0800
committer Shawn O. Pearce <sop@google.com> 1262469848 -0800

Add upsert to Access interface

Being able to update-or-insert a record makes it easier to avoid
using a Transaction in some cases.  SQL doesn't do upsert well,
but non-SQL systems like Apache Cassandra can.

For SQL we try to fake it by updating first, and if that fails,
performing an insert.  There is still a possible race condition,
a different thread could perform the insert between our update
failure and our insert attempt.

Change-Id: I384beda849cb815314530440e1bfdb502dadc95a
Signed-off-by: Shawn O. Pearce <sop@google.com>