There's an issue where we don't seem to have consensus yet, so I
figured I'd bounce it off the list.
If the SSI patch were to be accepted as is, REPEATABLE READ would
continue to provide the exact same snapshot isolation behavior which
both it and SERIALIZABLE do through 9.0, and SERIALIZABLE would
always use SSI on top of the snapshot isolation to prevent
serialization anomalies. In his review, Jeff argued for a
compatibility GUC which could be changed to provide legacy behavior
for SERIALIZABLE transactions -- if set, SERIALIZABLE would fall back
to working the same as REPEATABLE READ.
In an off-list exchange with me, David Fetter expressed opposition to
this, as a foot-gun. I'm not sure where anyone else stands on this.
Personally, I don't care a whole lot because it's trivial to add, so
that seems to leave the vote at 1 to 1. Anyone else care to tip the
scales?
-Kevin