python runtime_error ai_generated true

sqlalchemy.orm.exc.ConcurrentModificationError: Object '<User at 0x...>' is being merged into a Session but the same instance is already present

ID: python/sqlalchemy-orm-exc-concurrent-modification-error

Also available as: JSON · Markdown · 中文
80%Fix Rate
82%Confidence
0Evidence
2024-11-10First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
3.x active — — —

Root Cause

Attempting to merge an ORM instance that is already tracked by the same session, causing a conflict.

generic

中文

尝试合并一个已被同一会话跟踪的 ORM 实例，导致冲突。

Workarounds

  1. 80% success Check session identity map 
    Check if the instance is already in the session using session.is_modified() or track identities manually before merging.
  2. 90% success Merge with fresh instance 
    Use session.merge() with a new instance that has the same primary key, ensuring the session does not already contain it.

Dead Ends

Common approaches that don't work:

  1. Using add() instead of merge() 70% fail

  2. Expunging the instance first 50% fail