Document correct usage of a ResultIterator #85
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We receicently had [a panic in Consul](hashicorp/consul#9566) that was caused by incorrect usage of a ResultIterator. A minimal reproduction of this panic can be seen [here](https://github.com/hashicorp/go-memdb/compare/panic-delete-inside-iter). Many of us learned that there are undocumented rules for using a ResultIterator correct with a write transaction. This commit attempts to document that safe use of a ResultIterator.
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The panic happens because When the next call to Even without a panic, modifications to the tree can cause |
dnephin
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Jan 21, 2021
Previously this could panic anyway (see #85), but only when the nodse in an index line up in a very specify way. This meant that tests may not exercise the bug, and the panic would get into a release. By adding an explicit panic here we ensure that any basic test coverage of an iteration would fail. In the case of inserts it would not panic, but could return incorrect results (most likely duplicate). This panic ensures we fail instead of returning incorrect results. It would have been nice to error instead of panic, but there's no place in the current interface to return an error.
This was referenced Jan 21, 2021
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Last week we had a panic in Consul that was caused by incorrect usage of a ResultIterator. A minimal reproduction of this panic can be seen here.
Many of us learned that there are undocumented rules for using a ResultIterator correctly with a write transaction.
This commit attempts to document that safe use of a ResultIterator.