ActiveQuery::one() limiting database records

[hvta]

What steps will reproduce the problem?

ActiveQuery::one() doesn't seem to limit records in SQL.

What is the expected result?

Queries created with ActiveQuery::one() should have a LIMIT 1 clause in the prepared SQL.

What do you get instead?

The function selects all rows from a table resulting in excess memory consumption.

Additional info

Q	A
Yii version	2.0.?
PHP version
Operating system

[rob006]

See #9578

[rob006]

@samdark Maybe it is worth add some shortcut for that, like ActiveQuery::first()? Just see how many duplicates have #4348 or #9578.

[samdark]

Yeah... maybe.

[MysteryDragon]

As I see there were some attempts: #12563

[SamMousa]

I looked into some of the old issues but couldnt find the answer to this question:
What's the exact use case for selecting one record without a limit?

[bizley]

I think this is the potential problem - yiisoft/yii2#4348 (comment)

[SamMousa]

So can we create a specific test case to see if that's still true anno 2017?

Basically if that happens it is a bug in MySQL. The whole point of a dbms is to tell it what I want using SQL not how I want it...

If I only want one record I should tell the database and it is its responsibility to figure out the most efficient way to do that.

[MysteryDragon]

Pay attention on yiisoft/yii2#4348 (comment) also.
(And I'm not expert in MSSQL/Oracle at all.)

[samdark]

@SamMousa a test would be helpful.

[SamMousa]

Looking into that now.
It could have been this bug: https://bugs.mysql.com/bug.php?id=78325

I'm unable to get mysql to pick the wrong index when using 2 tables with 50 million records, then joining them with a limit of 1 and different sorting (both on index and non-index columns).

I imagine that if your limit is high and you use a sort / group at some point mysql decides that it will be too big to store in memory and uses on disk storage. This is however not related to the limit clause but to the sorting.

@samdark It's impossible to prove a negative so I won't try ;-)

[samdark]

MSSQL:

[samdark]

So it seems it doesn't matter for MSSQL... @sergeymakinen you're good with MSSQL. Any idea?

[sergeymakinen]

Most of the time (99%) it’s not an issue for MSSQL anymore. Especially in the yii\db\mssql\QueryBuilder::newBuildOrderByAndLimit() case. I consider limit(1) safe to be used in one().
I can neither confirm nor deny the same for Oracle but in recent versions (10.2 or higher) it should not be an issue.