[DOC] Supported ops page differentiate type supported in key vs passed along

[tgravescs]

Report incorrect documentation

The supported ops page doesn't seem to indicate if a type is supposed as the main key (like joining on) vs just being able to be passed along as another columns. Perhaps we should add a note for this.

[andygrove]

PR #3011 adds this information for types that cannot be usued as join keys in sort-merge, hash, and broadcast joins.

@tgravescs is that sufficient to address this issue or are there other types that need clarification?

[tgravescs]

so that sounds sufficient for joins but I wonder about other operations like hashAggregate, sorting, union, etc...

[revans2]

We can do the same thing for all of them. It is mostly a question of should the framework have a more generic way to do this, or should we add in one off solutions.

SparkPlan/Scala gives us a productIterator that we might be able to use to filter it to just expressions/sequences of expressions and then match those up with a pattern, similar to what we do when matching parameters to an Expression. That to me feels like a fairly generic way to make this work. But it is a lot of code compared to what is happening in #3011 along with the already existing check in the code.

    val keyDataTypes = (leftKeys ++ rightKeys).map(_.dataType)
    if (keyDataTypes.exists(dType =>
      dType.isInstanceOf[ArrayType] || dType.isInstanceOf[MapType])) {
      meta.willNotWorkOnGpu("ArrayType or MapType in join keys are not supported")
    }

So The difference would be something like

BroadcastHashJoinExec	Implementation of join using broadcast data	None	S	...	S	NS	NS	PS* (Cannot be used as join key; missing nested BINARY, CALENDAR, ARRAY, MAP, STRUCT, UDT)	PS* (Cannot be used as join key; missing nested BINARY, CALENDAR, ARRAY, MAP, STRUCT, UDT)	PS* (Cannot be used as join key; missing nested BINARY, CALENDAR, ARRAY, MAP, STRUCT, UDT)	NS

vs

BroadcastHashJoinExec	Implementation of join using broadcast data	LeftKeys	None	S	...	S	NS	NS	NS	NS	NS	NS
BroadcastHashJoinExec	Implementation of join using broadcast data	RightKeys	None	S	...	S	NS	NS	NS	NS	NS	NS
BroadcastHashJoinExec	Implementation of join using broadcast data	Output	None	S	...	S	NS	NS	PS* (missing nested BINARY, CALENDAR, ARRAY, MAP, STRUCT, UDT)	PS* (missing nested BINARY, CALENDAR, ARRAY, MAP, STRUCT, UDT)	PS* (missing nested BINARY, CALENDAR, ARRAY, MAP, STRUCT, UDT)	NS

[sameerz]

The latter / more generic approach that @revans2 mentions above seems like the better way to go.