Storage glossary · JSON corpus · llms.txt · hesela.com

write-skew · shipping

Write skew

Write skew is a concurrency anomaly in which transactions read overlapping data and make disjoint writes whose combined outcome can violate an invariant that each transaction would preserve alone.

It is possible under snapshot isolation without a same-row write conflict. Checking only the versions of the rows being written does not validate every cross-row read dependency.

Relations

related
snapshot-isolation, serializability

Citations

  1. Hal Berenson et al. A Critique of ANSI SQL Isolation Levels. ACM SIGMOD 1995; MSR-TR-95-51, section 4.2. (accessed 2026-10-12)
  2. Dan R. K. Ports and Kevin Grittner. Serializable Snapshot Isolation in PostgreSQL. PVLDB 5(12), 1850-1861, 2012, sections 2 and 4. arXiv:1208.4179v1. (accessed 2026-10-12)
  3. Storage consistency: ordering is not a transaction or a durability promise (accessed 2026-10-12)

JSON: /data/terms/write-skew.json