Explain why this procedure allows phantoms.
The following procedure has been proposed for obtaining read locks.
Whenever an SQL statement reads a set of rows that satisfies some predicate in a
table, the system first gets an IS lock on the table containing the rows and then
gets an S lock on each of the rows.
An INSERT or DELETE statement gets a non-conflicting IX lock on the table and X
locks on the tuples inserted or modified. The inserted tuples might satisfy the predicate but since they are newthere would be no lock conflict to delay the insert. Similarly the initial value of a modified tuple might not satisfy the predicate and so it would be possible to obtain an X
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