fix: error handling in Iterator.Next() method #1053
Conversation
WalkthroughThe changes update the Changes
Sequence Diagram(s)sequenceDiagram
participant Client as Client
participant Iterator as Iterator
participant T as iter.t
Client->>Iterator: Call Next()
Iterator->>T: Call next()
alt Error encountered
T-->>Iterator: Return error
Iterator->>Iterator: Set iter.err with error, set iter.t=nil, iter.valid=false
Iterator-->>Client: Return error state
else No error
T-->>Iterator: Return next item
Iterator-->>Client: Return next item
end
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what do you mean here? What is FastIterator? |
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FastIterator is another iterator implementation in this project (in fast_iterator.go) that properly stores errors in iter.err field. My PR makes Iterator.Next() handle errors the same way for consistency across all iterators in the codebase.
@technicallyty Hey, FastIterator is another iterator in this codebase (in fast_iterator.go) that already handles errors correctly by storing them in iter.err. I just made Iterator.Next() follow the same pattern for consistency. |
| if node == nil || err != nil { | ||
| iter.t = nil | ||
| iter.valid = false | ||
| if err != nil { |
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could you add a test to check if this error is being set now properly?
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Actionable comments posted: 0
🧹 Nitpick comments (2)
iterator_test.go (2)
425-429: Consider more deterministic node corruption.The current approach to finding a node to corrupt relies on the tree structure, which could make the test flaky if tree implementation changes. A more deterministic approach might be to iterate through multiple nodes and select a specific one.
- // We'll corrupt a node that would be retrieved in the next iteration - nodeToCorrupt = immutableTree.root.leftNodeKey - if nodeToCorrupt == nil { - nodeToCorrupt = immutableTree.root.rightNodeKey - } + // Find a node that we know will be traversed during iteration + for i := 0; i < 3 && goodIter.Valid(); i++ { + goodIter.Next() // Move through a few nodes + } + // Get a node from the current iterator position + nodeToCorrupt = goodIter.iter.node.hash
446-455: Iteration logic could be simplified.The current approach uses multiple conditionals and a loop with a fixed count to try to encounter the corruption. Consider a simpler approach that continues until the iterator becomes invalid or reaches the end.
- if iter.Valid() { - // If valid on first call, try moving to next nodes where it should encounter the corruption - iter.Next() - } - - // The iterator should now either be invalid with an error, or we need to continue - // traversal until encountering the corruption - for i := 0; i < 5 && iter.Valid(); i++ { - iter.Next() - } + // Continue iteration until we either encounter the corruption or reach the end + for iter.Valid() { + iter.Next() + }
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📒 Files selected for processing (2)
iterator.go(1 hunks)iterator_test.go(2 hunks)
🚧 Files skipped from review as they are similar to previous changes (1)
- iterator.go
🔇 Additional comments (3)
iterator_test.go (3)
4-4: Addition of fmt import is appropriate.The new import is used for string formatting in the TestIterator_ErrorPropagation test to create test keys and values.
386-461: Test effectively validates error handling in Iterator.Next()This well-structured test comprehensively verifies that the Iterator correctly propagates errors from the traversal to the iter.err field. The test:
- Creates a non-trivial tree structure
- Deliberately corrupts a node in the database
- Verifies that iteration becomes invalid and surfaces the appropriate error message
The test aligns perfectly with the PR objective of ensuring proper error handling in the Iterator.Next() method, mirroring FastIterator's error handling pattern. It also addresses the previous TODO about verifying error handling correctness.
458-460: LGTM! Correct error validation.The assertions correctly verify that the iterator becomes invalid and returns an appropriate error message when encountering corrupted node data.
This PR fixes the error handling in the Iterator.Next() method by properly storing the error in the iter.err field, similar to how it's done in FastIterator.
The TODO comment "double-check if this error is correctly handled" has been addressed by adding code to store the error in the iter.err field when an error occurs during the traversal.next() call.
This ensures that the error can be properly retrieved later via the Error() method, maintaining consistency with other iterator implementations in the codebase.
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