MySQL row lock parse (MySql lock mechanism)

Row lock (partial write)

Features:
bias InnoDB storage engine, lock large lock slow; there will be a deadlock; locking granularity smallest and lowest probability of lock conflicts, have the highest degree of concurrency.
The biggest difference InnoDB and MyISAM are two points: First, to support the transaction (TRANSACTION); the second is using row-level locking.

Affairs (Line Lock Support Services)

ACID properties of the transaction and its

problems caused by concurrent transactions:
update loss

dirty reads,

non-repeatable read (solutions to add a row lock)

phantom reads

transaction isolation level: (MYSQL default repeatable read)

case study:

Build SQL table

Line Lock Basic Presentation (add an index (row locks) do not have a full table scan to locate the line directly, using the primary key is the use of row locks)

different rows updated no problem

No index, row lock escalation to a table lock
varchar type b written in a numeric column index failed to make at this time session 2-operation will be stepping into a different line of waiting

gap lock Hazard


face questions: How often test a row lock

Case Conclusion

Row lock analysis

Optimization Tips

1. As far as possible to retrieve all the data are done by the index, the index line to avoid no lock escalation to a table lock.
2. Rational design of the index, minimizing lock range
3. As a search condition is less, to avoid gaps lock
4. Try to control the size of the transaction, and the length of time to reduce the amount of resources locked
5. The transaction isolation level as low as possible