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Editorial Team
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Asked: 2026-06-15T05:25:53+00:00

I have a problem finding a detailed explanation of datastore behaviour in the following

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I have a problem finding a detailed explanation of datastore behaviour in the following scenario.

  1. A transaction is started
  2. Some changes are made
  3. Another, independent, transaction is started using ndb.TransactionOptions.INDEPENDENT propagation level. It’s purpose is to increment a sharded counter. I need it as a nested transaction, because I’ll have many counters and it’s only possible to use 5 entity groups in one transaction
  4. Nested transaction is committing successfully
  5. Main transaction is trying to commit, but fails
  6. Main transaction is committing after some retries

I suppose that nested transaction is run only once, but I cannot verify this assumption.
Does anybody know how it works?

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1 Answer

  1. Editorial Team

    Put some logging statements in to see the behavior. If steps 3-4 are initiated by the code of the main transaction, the independent transaction will be started each time the main transaction is retried. That’s why it’s called INDEPENDENT, not NESTED.

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