Transaction isolation when selecting, inserting, deleting

Question

What could be wrong in the next transaction if executed by concurrent users at the default isolation level READ COMMITTED?

BEGIN TRANSACTION

SELECT * FROM t WHERE pid = 10 and r between 40 and 60
-- ... this returns tid = 1, 3, 5
-- ... process returned data ...
DELETE FROM t WHERE tid in (1, 3, 5)
INSERT INTO t (tid, pid, r) VALUES (77, 10, 35)
INSERT INTO t (tid, pid, r) VALUES (78, 10, 37)
INSERT INTO t (tid, pid, r) VALUES (79, 10, 39)

COMMIT

Answer 1

You may have serious performance issues from dead castles

SELECT will receive a shared lock on the page, and then DELETE will try to update these locks to exclusive locks.

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Answer 2

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Answer 3

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Answer 4

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