Does VoltDB support unique indexes?

Our schema has a USER table...

USER( 
   userId,
   firstname,
   lastname,
   email)

and we want to ensu开发者_开发百科re all user's have unique email addresses. Is it possible to create a unique index in VoltDB to enforce this constraint?

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VoltDB supports primary key indexes (which are always unique) as well as secondary indexes that can be defined as unique.

For your particular table you have two choices to enforce uniqueness on the email column:

1. Define the USER table as replicated.
2. Partition the USER table on the email column.

If you create a unique index on email and partition the table on userId then the uniqueness enforcement of the email column will be within individual partitions.

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VoltDB provides implicit indexes for primary keys. For example if you assign userID as a primary key then userID will be unique (because of VoltDB's implicitly index assignment on primary key) but to make email column as unique you have to explicitly assign constraint 'UNIQUE' on email column. Similarly suppose you are partitioning a table and partitioning is done on column userID then to enforce email to be unique in every partition, you should explicitly assign 'ASSUMEUNIQUE' constraint on email column.