We have used i64 before because that is the size of an integer in
SQLite. However, I believe that for large enough databases, the chances
of collision here are just too high. The effect of a collision is the
database silently returning incorrect data in the materialized view.
So now that everything else is working, we should move to i128.
The Merge operator is a stateless operator that merges two deltas.
There are two modes: Distinct, where we merge together values that
are the same, and All, where we preserve all values. We use the rowid of
the hashable row to guarantee that: In Distinct mode, the rowid is set
to 0 in both sides. If they values are the same, they will hash to the
same thing. For All, the rowids are different.
The merge operator is used for the UNION statement, which is a
cornerstone of Recursive CTEs.
