thanks for the good documentation of the various database file formats. The wal
index one is a bit unclear to me in a few spots, maybe someone can help me out?
2.1. The WAL-Index Header
there is a second copy of the WAL index information, but it's not specified
what to do with that information. Can it be ignored? Does it have to be
2.1.3. WAL Locks
does a read connection usually keep a read lock on WAL_READ_LOCK(0), and
switch to any of WAL_READ_LOCK(1..4) when it starts a transaction? Does that
also mean there is a maximum of 4 concurrent read-only transactions?
2.2. WAL-Index Hash Tables
I think I figured out how it works, but both explanations of the hashing
algorithm doesn't use the `aHash` field. It's either unclear or wrong :)
(e.g., in point 2., `aPgno[j%8192]!=0` should be `aHash[j%8192]!=0` if I
understand things correctly)