write skew

RU: write skew (асимметричная запись)

A concurrency anomaly that arises under snapshot isolation but is not one of the three SQL-standard anomalies (dirty read, non-repeatable read, phantom). Two transactions each read an overlapping data set, make decisions based on the combined state, and write to non-overlapping rows; both commits succeed, producing a result that no serial execution could have generated. Prevented only by SERIALIZABLE isolation (SSI in PostgreSQL).