Minor: change the sort merge join emission as incremental

[berkaysynnada]

Which issue does this PR close?

Closes #.

Rationale for this change

Since SortMergeJoin appears only when the inputs are sorted, marking its emission type as incremental would reflect its behavior better.

What changes are included in this PR?

Are these changes tested?

Are there any user-facing changes?

[ozankabak]

LGTM - this is a bugfix as SMJ always emits incrementally

[alamb]

I wonder if there is some way / reason to test this (I realize it just a property, I was worried it might be broken in the future)

[berkaysynnada]

I wonder if there is some way / reason to test this (I realize it just a property, I was worried it might be broken in the future)

AFAIK SMJ is not very stable and it is getting update frequently. Once it becomes stabilized, then it will be more meaningful to assign a property based on a more comprehensive analysis (perhaps it may behave like both incremental and final)

[alamb]

I wonder if there is some way / reason to test this (I realize it just a property, I was worried it might be broken in the future)

AFAIK SMJ is not very stable and it is getting update frequently. Once it becomes stabilized, then it will be more meaningful to assign a property based on a more comprehensive analysis (perhaps it may behave like both incremental and final)

Maybe we can figure out how to write a test that mimics whatever you are doing with these properties (e.g. run a plan end to end that requires the plan to emit data incrementally or something) 🤔