Hi
When hashJoin operators are the best to use?
I think join hints are the only direct way to you can tell the planner to use a NodeHashJoin.
Often I find that hash joins in the plan can be problematic as far as query time and GCs, but they can be useful when you explicitly have a small set of start and end nodes, and when you have a known supernode between them, where the cost to expand out from the supernode is expensive, compared to the cost to only traverse to the supernode.
I have a knowledge base article which describes this scenario:
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