1 · MongoDB · WHEN A COPY IS NOT A DUPLICATE
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Three Types of Redundant Data
UNCHANGEABLE
HISTORICAL
CURRENT COPIES
Do not change according to the rules
They change, but the copy should remain the same
The copy should keep up with the source
ID that cannot be changed.
Synchronization isn't necessary, but they do describe the guarantee and how to correct an incorrect entry.
price_paid, level_at_purchase, username at the time of the match.
Strictly speaking, this isn’t a copy, but a separate account of how it was back then.
Current price, current nickname, total burn effect.
Sword: 5 or 6 damage? We do not synchronize the `stats.damage` property. In another model, `effects.burn` is a copy: a value of 5 when the source is 6 requires an update; the snapshot of the purchase value (5) remains correct.