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Test for chunk not found - #4382

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Test for chunk not found#4382
kennethjor wants to merge 3 commits into
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kennethjor:chunck-not-found

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@kennethjor

@kennethjor kennethjor commented Sep 1, 2026 •
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Test PR to reproduce a chunk not found error:

Exception in thread "main" org.h2.mvstore.MVStoreException: Chunk 6 not found [2.4.240/9]
	at org.h2.mvstore.DataUtils.newMVStoreException(DataUtils.java:996)
	at org.h2.mvstore.FileStore.getChunk(FileStore.java:2015)
	at org.h2.mvstore.FileStore.readPage(FileStore.java:1962)
	at org.h2.mvstore.MVStore.readPage(MVStore.java:1143)
	at org.h2.mvstore.MVMap.readPage(MVMap.java:632)
	at org.h2.mvstore.Page$NonLeaf.getChildPage(Page.java:1158)
	at org.h2.mvstore.Cursor.hasNext(Cursor.java:64)
	at org.h2.mvstore.MVMap$2$1.hasNext(MVMap.java:745)
	at org.h2.test.store.TestMVStoreChunkNotFound.test(TestMVStoreChunkNotFound.java:65)
	at org.h2.test.TestBase.testFromMain(TestBase.java:479)
	at org.h2.test.store.TestMVStoreChunkNotFound.main(TestMVStoreChunkNotFound.java:28)

I have confirmed the test fails off master as well.

I'm not familiar with the codebase enough to actually attempt a fix.

@kennethjor

kennethjor commented Sep 1, 2026

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Failing run based on 2.4.240: https://github.com/kennethjor/h2database/actions/runs/33464576215/job/99721669453#step:4:413

@kennethjor

kennethjor commented Sep 1, 2026

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Failing run off master: https://github.com/kennethjor/h2database/actions/runs/33464900580/job/99722620056#step:4:382

ERROR: FAIL (memory ) org.h2.mvstore.MVStoreException: Chunk 6 not found [2.5.259/9] org.h2.mvstore.MVStoreException: Chunk 6 not found [2.5.259/9] ------------------------------
org.h2.mvstore.MVStoreException: Chunk 6 not found [2.5.259/9]
	at org.h2.mvstore.DataUtils.newMVStoreException(DataUtils.java:998)
	at org.h2.mvstore.FileStore.getChunk(FileStore.java:2024)
	at org.h2.mvstore.FileStore.readPage(FileStore.java:1989)
	at org.h2.mvstore.MVStore.readPage(MVStore.java:1158)
	at org.h2.mvstore.MVMap.readPage(MVMap.java:632)
	at org.h2.mvstore.Page$NonLeaf.getChildPage(Page.java:1203)
	at org.h2.mvstore.Cursor.hasNext(Cursor.java:64)
	at org.h2.mvstore.MVMap$2$1.hasNext(MVMap.java:745)
	at org.h2.test.store.TestMVStoreChunkNotFound.test(TestMVStoreChunkNotFound.java:65)
	at org.h2.test.TestBase.runTest(TestBase.java:147)
	at org.h2.test.TestAll.addTest(TestAll.java:998)
	at org.h2.test.TestAll.testUtils(TestAll.java:920)
	at org.h2.test.TestAll.runTests(TestAll.java:617)
	at org.h2.test.TestAll.testAll(TestAll.java:553)
	at org.h2.test.TestAll.run(TestAll.java:494)
	at org.h2.test.TestAll.main(TestAll.java:438)

@kennethjor

kennethjor commented Sep 1, 2026 •
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Removed as many custom configurations from the MVStore setup as possible in 5b9f934. The following are required for the test to break. Disabling either of these will make the test pass:

store.setVersionsToKeep(0);
store.setRetentionTime(0);

@kennethjor kennethjor mentioned this pull request Sep 1, 2026
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@kennethjor

kennethjor commented Sep 1, 2026 •
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cfefa3b removes a bit more from the test. Writing to the store isn't required, just doing repeated commits and compacts is enough to trigger it.

@andreitokar

andreitokar commented Sep 1, 2026

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I think, this case demonstrates the issue with incomplete use of MVStore API, rather than actual problem.
Iterator loop need to be wrapped with this pare of MVStore.de/registerVersionUsage() :

MVStore.TxCounter txCounter = store.registerVersionUsage();
Iterator<Map.Entry<String, String>> it = map.entrySet().iterator();
while (it.hasNext()) {
    it.next();
...
    }
}
store.deregisterVersionUsage(txCounter);

Otherwise every version, except the current one, is considered as "not in use" and eligible for collection.

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@kennethjor @andreitokar