Chen Luo created ASTERIXDB-2522:
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Summary: Skip logging WAIT record during lock conflicts
Key: ASTERIXDB-2522
URL: https://issues.apache.org/jira/browse/ASTERIXDB-2522
Project: Apache AsterixDB
Issue Type: Improvement
Components: TX - Transactions
Reporter: Chen Luo
Assignee: Chen Luo
Currently, our deadlock-free locking protocol
(https://cwiki.apache.org/confluence/display/ASTERIXDB/Deadlock-Free+Locking+Protocol)
is conservative. It works as follows:
A writer thread (i.e., transactor) first tries to acquire X lock on a primary
key.
If the try lock fails, it should release all previous held locks before
acquiring the X lock. To release previous locks, the transactor pushes partial
frames so that previous records can be committed, and further log a WAIT record
to wait for the log flusher to force all previous log records and unlock
previous locks.
However, the WAIT record is actually not necessary. After committing previous
records, the locks will eventually be released by the log flusher thread. As a
result, deadlock still cannot happen in this case.
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