Data Warehouse Update Issue

time:

process:

DU:

DU1 from IS1

DU2 from IS2

QR from IS2

• Middle Layer received two data updates in a specific order ( DU1 < DU2 )

• The commit order of processing these two data updates is different ? Conflict Problem

• Idea: Counter allows negative value, and system removes the tuple when its counter is 0.

• When: Tuple to be deleted doesn’t exist in extent.

• Reason: Negative Counter will keep the tuples that should be deleted in the future.

• Lemma: Negative counters will only temporarily appear in DW when commit order is varied.

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