FA-44617 / Data systems / Member archive

A simultaneous join update counts the delta-delta product twice · case 02

A simultaneous join update counts the delta-delta product twice.

Member previewVariant 2 · 3 implementations · 7 checks per implementation

Case contract

Apply simultaneous signed changes to two bag relations. Emit the consolidated join delta Ldelta*Rold + Lold*Rdelta + Ldelta*Rdelta. Inputs are [key,value,weight]; ordinary non-null equality joins. Return sorted [leftvalue,rightvalue,weight] nonzero rows.

Why this case matters

A bounded deterministic data engine model makes representation and changelog faults reproducible.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
simultaneous insert	`[[2, 3, 2]]`	`[[2, 3, 1]]`	Failed

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