May be this is a newbie question but want to confirm as this is important for my app:

I'm using MySQLdb on Python and my code looks like:

db = MySQLdb.connect("localhost","root","",test)
cursor = db.cursor()

cursor.execute("UPDATE users SET address = 'Something' WHERE name = 'Someone'")
db.query("SELECT * FROM users WHERE address = 'Something'")

So the question is, will sample contain the row that was changed by the uncommitted update?

In the real app, I am making some complex queries with subclauses like GROUP_CONCAT, etc. Will all these work with uncommitted updates? (In the sense that can these work on the rows updated by uncommitted updates)

  • Where is the BEGIN and COMMIT? – Rick James Apr 6 '16 at 5:13

tl;dr Yes, sample will contain the rows that were just updated.

Please note that you're not in a transaction context. So every query is an implicit transaction in this specific case.

Assuming you did have a begin somewhere sample would still see the rows because it's the same connection and the same transaction.

If you started the transaction and opened a separate connection or you had a concurrent process/request it would only see the rows without commit if your mysql is running with READ-UNCOMMITTED transaction level.

You can check the global settings by:

mysql> show global variables like 'tx_isolation';

It can also be set for individual connection:

mysql> set tx_isolation='READ-UNCOMMITTED';

I hope this answers your question.

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