Hasty Briefsbeta

Understanding conflict resolution and avoidance in PostgreSQL: a complete guide

11 days ago
  • #Distributed Databases
  • #Conflict Management
  • #Postgres
  • Bi-directional logical replication in Postgres 16 introduces functionality to replicate data between two tables from different publishers, but it's not implicitly safe for Active-Active clusters.
  • Distributed Postgres clusters face challenges like sequence rules, data merging concerns, conflict management, and potential node divergence, which can lead to data loss.
  • CAP theorem and PACELC principle explain the trade-offs in distributed databases between consistency, availability, and partition tolerance, with network latency adding complexity.
  • Conflicts in distributed Postgres clusters can be categorized into naturally convergent, resolvable, divergent, and phantom conflicts, each requiring different handling strategies.
  • Techniques to mitigate conflicts include controlling write targets, using Conflict Resistant Data Types (CRDTs), and implementing key management strategies like sequence offsets or globally unique keys.
  • CRDTs help manage numeric column conflicts by applying diffs between incoming and existing values or using custom data types with per-node hidden fields.
  • Key management strategies to avoid surrogate key conflicts include sequence offsets, globally unique keys (UUIDs, Snowflake IDs), and global allocations.
  • Identity columns in Postgres, while standard SQL, may not be flexible enough for distributed clusters, requiring alternative approaches like explicit sequence usage.
  • Divergent conflicts, especially involving DELETE or TRUNCATE, can be mitigated by converting UPDATEs to INSERTs or using soft deletes instead of physical deletions.
  • Advanced techniques like tombstone records and leveraging Postgres' MVCC can help manage visibility and prevent divergent conflicts in distributed clusters.