f0:string f1:int f2:int f3:double (all can be null)
f1:partition key
no bucket key
bucket count: -1
global bitmap index: f0

Msgs:
snapshot-1
Add: Alice, 10, 1, 11.1
Add: Bob, 10, 1, 12.1
Add: Emily, 10, 0, 13.1
Add: Tony, 10, 0, 14.1
Add: Lucy, 20, 1, 15.1
Add: Bob, 10, 1, 16.1
Add: Tony, 20, 0, 17.1
Add: Alice, 20, null, 18.1
NoCompact

snapshot-1: with no index
snapshot-2: with f0 global bitmap index for f1=10

commit_messages-01:
f0 global bitmap index for f1=10 while commit snapshot 2
