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| LHS Event (key, extracted fk) | To which RHS-partition? | RHS-0 State | RHS-1 State | Inner Join Output | Left Join Output | Execute Join Logic? | Notes | Inner-Join SubscriptionWrapper Instruction | |
|---|---|---|---|---|---|---|---|---|---|
| Publish new event | (k,1) | RHS-0 | (1,foo) | (k,1,foo) | (k,1,foo) | Inner/Left | Normal fk-join induced by LHS event | to RHS-0: | |
| Publish update to event by changing fk | (k,1) → (k,2) | RHS-1 | (1,foo) | (k,null) | (k,JoinResult2,null) | LEFT | Must indicate a delete because there is currently no (fk,value) in RHS with key=2, and (k,1,foo) is no longer valid output. | to RHS-0: DELETE_KEY_NO_PROPAGATE to RHS-1: | |
Publish update to event | (k,2) → (k,3) | RHS-0 | (1,foo) | (k,null) | (k,3,JoinResultnull) | LEFT | Ideally would not publish a delete with Inner Join, but we do not maintain sufficient state to know that the (k,2) update resulted in a null output and we don't need to do it again. | to RHS-0: DELETE_KEY_NO_PROPAGATE to RHS-1: | |
| Publish a value to RHS-0 | - | - | (1,foo) | (k,3,bar) | (k,3,bar) | Inner/Left | Performs prefix scan join | - | |
| Delete k | (k,3) → (k,null) | RHS-0 | (1,foo) | (k,null) | (k,JoinResultnull,null) | LEFT | Propagate null/delete through the sub-topology | to RHS-0: DELETE_KEY_AND_PROPAGATE | |
| Publish original event again | (k,null) → (k,1) | RHS-0 | (1,foo) | (k,1,foo) | (k,1,foo) | Inner/Left | Normal fk-join induced by LHS event | to RHS-0: | |
| Publish to LHS | (q,10) | RHS-1 | (1,foo) | Nothing | (q,JoinResultnull,10) | LEFT | Only real Significant difference between Inner and Outer | - | |
| Publish a value to RHS-1 | - | - | (1,foo) | (q,baz) | (q,10,baz) | (q,10,baz) | Inner/Left | Normal fk-join induced by LHS event | to RHS-1: |
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