fix(spanner): prevent deadlock if ResultSet#next() is never called (step 5)#5654
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olavloite merged 6 commits intoMay 13, 2026
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…tep 5) If a query included a BeginTransaction option and the application never called ResultSet#next(), then the transaction ID would never be returned. This would block any other query from using the transaction. This change refactors ResultSet to use a background worker to read from the stream. This prevents that a deadlock can happen if the application does not call ResultSet#next(). It also allows the application to call ResultSet#metadata() without first calling ResultSet#next(). Finally, it also allows the ResultSet to decode data from the server asynchronously while the application processes rows that it has already read from the ResultSet. Replaces googleapis#5324 due to too massive merge conflicts.
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## main #5654 +/- ##
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- Coverage 97.92% 97.92% -0.01%
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Files 221 222 +1
Lines 52759 53183 +424
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+ Hits 51663 52077 +414
- Misses 1096 1106 +10 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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Code Review
This pull request refactors ResultSet to utilize a background worker task for stream processing, making ResultSet::metadata asynchronous and fixing a potential deadlock in lazy transaction starts. Review feedback identifies that ResultSet is no longer Sync due to the new mpsc::Receiver field, which may break existing code, and notes a style guide violation concerning the use of unwrap() in production logic.
sakthivelmanii
approved these changes
May 13, 2026
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If a query included a BeginTransaction option and the application never called ResultSet#next(), then the transaction ID would never be returned. This would block any other query from using the transaction. This change refactors ResultSet to use a background worker to read from the stream. This prevents that a deadlock can happen if the application does not call ResultSet#next(). It also allows the application to call ResultSet#metadata() without first calling ResultSet#next(). Finally, it also allows the ResultSet to decode data from the server asynchronously while the application processes rows that it has already read from the ResultSet.
Replaces #5324 due to too massive merge conflicts.