Confirm NULLIF Behavior

[natashasehgal]

Want to confirm if the NULLIF(a,b) in Presto coordinator translates to if(eq(a, b), null, a) 100% of the time.
Or is there any nuance which will require preserving NULLIF and not converting to IF?

This question came up in the development of Axiom native front-end for Velox.
facebookincubator/axiom#781 (comment)

Also follow up, is there any difference in implementing this in Axiom as a function (current PR above) or expression?

Possible Implementation

https://github.com/prestodb/presto/blob/master/presto-parser/src/main/java/com/facebook/presto/sql/tree/NullIfExpression.java

[natashasehgal]

cc @kaikalur

[natashasehgal]

cc @tdcmeehan @mbasmanova

[kaikalur]

No and also there are some other things - see SqlToRowExpressionTranslator.java - there are a ton of these special things - someone recently found LIKE is translation is not ideal for native. So maybe we have a separate translator for native?

CC: @feilong-liu