Scavenging the mail folder uncovered Randall F. Kern's letter:
Read committed is faster, but I have not done any tests to know how much
faster. Read committed mode doesn't support concurrent updates either,
but fails silently. In other words, given to concurrent queries:
update foo set a
Scavenging the mail folder uncovered Randall F. Kern's letter:
[snip]
Concurrent updates are not supported in the serializable transaction
mode; if one transaction tries to update (or delete) a row that has
already been updated by a concurrent uncommitted transaction, the second
transaction
