Do UPDATEs block SELECTs?

I need to query a frequently updated record, does it wait until all updates finish?

• /updateUser/1

  Many requests are sent

  UPDATE users SET count = count + 1 WHERE id = 1 LIMIT 1
  

• /getUser/1

  While the user is being updated i perform this request

  SELECT * from users WHERE id = 1 LIMIT 1
  

The Solutions:

Below are the methods you can try. The first solution is probably the best. Try others if the first one doesn’t work. Senior developers aren’t just copying/pasting – they read the methods carefully & apply them wisely to each case.

Method 1

By default, writers do not block readers. So no, the SELECT would not have to wait for the UPDATE to finish.

Exception cases:

• If you use explicit syntax to make the SELECT a locking read query.

• If you set the transaction isolation level to SERIALIZABLE, which has the effect that all SELECTs are implicitly locking reads.

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