Code reviewHardcr-g644

Subject Database deadlockLevel Senior–Staff~28 minCommon in Databases & SQL · Concurrency interviewsIndustries Software development

Question

Review this Java money-transfer method.

This runs on many threads; transfers go in both directions between the same accounts.

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Code to reviewjava

1void transfer(Connection conn, long fromId, long toId, long amount) throws SQLException {2    conn.setAutoCommit(false);3    lockAndDebit(conn, fromId, amount);   // SELECT ... FOR UPDATE on fromId, then UPDATE4    lockAndCredit(conn, toId, amount);    // SELECT ... FOR UPDATE on toId, then UPDATE5    conn.commit();6}

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