HIVE-22074: Slow compilation due to IN to OR transformation

[vineetgarg02]

No description provided.

[jcamachor]

Instead of obtaining the conf object here statically, let's just pass the int value using the ctx.

[vineetgarg02]

@jcamachor ctx is passed on to genExprNode by the callers. There are several callers which uses genExprNode. For this we will have to update all of these callers to set the config in TypeCheckCtx.
Fetching HiveConf only occurs if the expression at hand is GenericUDFIn and CBO wasn't executed therefore this shouldn't add much overhead.
Let me know if you think otherwise

[jcamachor]

I think it is better to pass this value from the callers in the context. You would not need to change all callers; if value is not passed, rewriting could be skipped. I see mainly two advantages of doing this:

1. if transformation is never happening, we will not be retrieving the conf and this value for every IN clause in a query (note that isCBOExecuted method is misleading, the value returned is foldExpr boolean which is false sometimes even for calls coming from CBO cf. first line in genFilterRelNode method in CalcitePlanner), and
2. removing the static call to Hive object from within the folding logic.

I see there are other calls to Hive.get() in the class, that information should probably be moved to context too.
These can all be tackled together in a follow-up, but I think since we are cleaning up this logic, it would make sense to do it at some point.

[vineetgarg02]

Ok. I'll create a separate jira and tackle this in a follow-up.

[vineetgarg02]

@jcamachor I have created https://issues.apache.org/jira/browse/HIVE-22135 for refactoring Hive.get().getConf().
For the current patch I have gotten green run. Let me know if everything looks good to you.