MySQL Bugs: #6606: Add safe_join setting to prevent cartesian products

Bug #6606	Add safe_join setting to prevent cartesian products
Submitted:	13 Nov 2004 14:50	Modified:	17 Jul 2008 22:17
Reporter:	Arjen Lentz	Email Updates:
Status:	Verified	Impact on me:	None
Category:	MySQL Server: General	Severity:	S4 (Feature request)
Version:	6.0	OS:	Any (any)
Assigned to:		CPU Architecture:	Any
Tags:	cartesian product, join, safe_join

Description:
- MySQL has for a long time had a safe_update setting (aka i-am-a-dummy) to prevent using UPDATE or DELETE without a key.
- MySQL 5.0 has a query_timeout setting.

New feature request:
A safe_joins setting, which would return an error if the server detects cartesian products.
This can't be found by the parser I suppose, but it should be detectable in/after the optimizer and before query execution.
The error could be "Table %s joined without a join condition"

This would be helpful to users.

How to repeat:
See description

Hmm I misread something, 5.0 does not have a query_timeout.
I do believe there were some ideas for this though.
But anyway... the idea stands.

Thank you for a resonable feature request. But even with this feature in place, nobody will prevent users from joins on condition that is true for all rows in both tables. I think, some kind of resources profiles support, that limits disk and CPU usage will serve users better.

Updated for 6.0 since it's obviously not going into an earlier version (since 2004...)

I would like to vote for this feature as well. I have a vary large database that occasionally gets locked up because someone who is not SQL savvy writes a bad query that skips needed table joins.