test: add unit test for distinct value retrieval in LSM index #2330
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Summary of Changes
Hello @robfrank, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!
This pull request introduces a new unit test to validate the integrity of results returned when querying non-unique LSM tree indexes. The test ensures that even when multiple documents share the same indexed key, the database correctly retrieves distinct documents, preventing any spurious duplicates in the result set.
Highlights
- New Unit Test for LSM Index: A new JUnit 5 test file,
Issue2328Test.java, has been added to theenginemodule. This test focuses on verifying the behavior of LSM (Log-Structured Merge-tree) indexes. - Distinct Value Retrieval Verification: The
notUniqueShouldReturnDistinctValuestest method specifically checks that when querying a non-unique LSM index, the result set does not contain duplicate documents. It achieves this by populating the database with documents where the indexed key (p2) is intentionally duplicated across multiple documents, but a different property (p1) remains unique per document. The test then asserts that allp1values retrieved from the query are distinct.
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Code Review
This pull request adds a new unit test to verify that queries on a non-unique LSM index return distinct records. The test logic is sound. I've provided a few suggestions to improve the test code's quality and maintainability by adhering to common testing best practices.
| final File tmp = File.createTempFile("ArcadeTmp", ""); | ||
| tmp.delete(); |
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This method of creating a temporary directory path has a potential race condition and does not guarantee cleanup of the database files after the test runs. It's recommended to use JUnit 5's @TempDir annotation, which provides a temporary directory and handles its cleanup automatically.
| System.out.println("Tmp Database: " + tmp); | ||
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| try(final DatabaseFactory fact = new DatabaseFactory(tmp.toString())){ | ||
| try(final LocalDatabase local = (LocalDatabase) fact.create()){ |
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It's a good practice to program against interfaces rather than concrete implementations. The fact.create() method returns a Database, and all subsequent calls on local are available on the Database interface. Casting to LocalDatabase is unnecessary here and makes the code more flexible.
| try(final LocalDatabase local = (LocalDatabase) fact.create()){ | |
| try(final Database local = fact.create()){ |
| System.out.println("Found: " + count); | ||
| System.out.println("Duplicates: " + dup); |
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While System.out.println is useful for debugging, it's generally better to avoid it in unit tests as it can clutter the output of test runs. This applies to other println calls in this test as well (lines 25, 72, 80). Consider removing them.
| if(dup>0) { | ||
| throw new IllegalStateException("Duplicates found: " + dup); | ||
| } |
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It's better to use JUnit assertions in tests instead of throwing an exception. This provides better integration with testing frameworks and build tools, often giving more informative failure reports.
org.junit.jupiter.api.Assertions.assertEquals(0, dup, "Duplicates found: " + dup);
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What does this PR do?
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Checklist
mvn clean packagecommand