Pass timestamp through SEQUENCE methods of ConnectionQueryService

[jtaylor-sfdc]

Currently SEQUENCES won't work if a connection has an SCN

[jtaylor-sfdc]

This is somewhat tricky, as it doesn't seem right to use the same timestamp as the connection. Probably better would be to have a fixed timestamp stored on the sequence itself. This is the timestamp that will always be used. If the sequence is deleted, a global counter is incremented and the next sequence created will use that timestamp. This prevents the deletion of a sequence from hiding the recreation of it.

A better alternative is to mark a sequence as deleted through the Put of PDataType.FALSE_BYTES in our QueryConstants.EMPTY_COLUMN_BYTES column. Creation would flip this back to PDataType.TRUE_BYTES and reset the CURRENT_VALUE to the starting value. In this way, we never issue a Delete and avoid the "hiding" issue and can always use the same timestamp (MetaDataProtocol.MIN_TABLE_TIMESTAMP).

[jtaylor-sfdc]

Argh. The Increment APIs in HBase don't allow a timestamp to be passed through. To implement this properly, we'll need to add our own coprocessor. We can solve the lack of notification if the row being incremented doesn't exist bug as well.

Here's my take on how sequences should work:

• On the client, cache the INCREMENT_BY amount and the KeyValue create timestamp. Make sure to use the SCN timestamp on the connection if provided at creation time.
• When incrementing, use the KeyValue create timestamp (as point-in-time queries should see the current value of the sequence, not based on the timestamp when the sequence was incremented).
• A drop of the SEQUENCE just issues a Delete of the row as is done now, but we should make sure that if an SCN timestamp is on the connection, we provide it at creation time.

[jtaylor-sfdc]

Fixed in master