FA-167 / Storage and queries / Member archive

Updating a materialized summary adds the replacement without removing the old value · case 02

A materialized total accumulates superseded row values, while an attempted repair also counts updates as new rows.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

Given a valid starting [sum,row_count] and an ordered list of [old_value,new_value] changes, return the updated pair. None means the row is absent, not a nullable stored value. Changes are valid and applied exactly once; no deduplication is requested.

Why this case matters

Models incremental maintenance of a materialized aggregate under insert, delete and replacement operations. It separates sum deltas from cardinality deltas and does not model concurrent lost updates or transaction replay.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
replacement changes sum but not row count	`[8, 2]`	`[6, 1]`	Failed

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