H2 - General error: "java.lang.NullPointerException" [50000-182]

Question

I have a quite big (>2.5 GB) h2 database file. Driver version is 1.4.182. Everything worked fine but recently the DB stop to work with exception:

Błąd ogólny: "java.lang.NullPointerException"
General error: "java.lang.NullPointerException" [50000-182] HY000/50000 (Help)
org.h2.jdbc.JdbcSQLException: Błąd ogólny: "java.lang.NullPointerException"
General error: "java.lang.NullPointerException" [50000-182] 
    at org.h2.message.DbException.getJdbcSQLException(DbException.java:345) 
    at org.h2.message.DbException.get(DbException.java:168) 
    at org.h2.message.DbException.convert(DbException.java:295) 
    at org.h2.engine.Database.openDatabase(Database.java:297) 
    at org.h2.engine.Database.<init>(Database.java:260) 
    at org.h2.engine.Engine.openSession(Engine.java:60) 
    at org.h2.engine.Engine.openSession(Engine.java:167) 
    at org.h2.engine.Engine.createSessionAndValidate(Engine.java:145) 
    at org.h2.engine.Engine.createSession(Engine.java:128) 
    at org.h2.engine.Engine.createSession(Engine.java:26) 
    at org.h2.engine.SessionRemote.connectEmbeddedOrServer(SessionRemote.java:347) 
    at org.h2.jdbc.JdbcConnection.<init>(JdbcConnection.java:108) 
    at org.h2.jdbc.JdbcConnection.<init>(JdbcConnection.java:92) 
    at org.h2.Driver.connect(Driver.java:72) 
    at org.h2.server.web.WebServer.getConnection(WebServer.java:750) 
    at org.h2.server.web.WebApp.test(WebApp.java:895) 
    at org.h2.server.web.WebApp.process(WebApp.java:221) 
    at org.h2.server.web.WebApp.processRequest(WebApp.java:170) 
    at org.h2.server.web.WebThread.process(WebThread.java:137) 
    at org.h2.server.web.WebThread.run(WebThread.java:93) 
    at java.lang.Thread.run(Thread.java:722) 
Caused by: java.lang.NullPointerException 
    at org.h2.mvstore.db.ValueDataType.compare(ValueDataType.java:102) 
    at org.h2.mvstore.MVMap.compare(MVMap.java:741) 
    at org.h2.mvstore.Page.binarySearch(Page.java:388) 
    at org.h2.mvstore.MVMap.put(MVMap.java:179) 
    at org.h2.mvstore.MVMap.put(MVMap.java:133) 
    at org.h2.mvstore.db.TransactionStore.rollbackTo(TransactionStore.java:491) 
    at org.h2.mvstore.db.TransactionStore$Transaction.rollback(TransactionStore.java:785) 
    at org.h2.mvstore.db.MVTableEngine$Store.initTransactions(MVTableEngine.java:223) 
    at org.h2.engine.Database.open(Database.java:736) 
    at org.h2.engine.Database.openDatabase(Database.java:266) 
... 17 more 

The problem occurs in my application and using H2 web frontend. I have tried solution from similar question but I cannot downgrade H2 to 1.3.x as it cannot read 1.4.x DB files.

My questions are:

How to handle it? Is it to possible to make it work again? I have tried downgrade H2 to 1.4.177 but it didn't help.

Is there any way to at least recover data to other format? I could use other DB (Sqlite, etc.) however I would need a way to get to these data.

EDIT: updated stacktrace

EDIT 2: Result of using Recovery tool:

$ java -cp h2-1.4.182.jar org.h2.tools.Recover
Exception in thread "main" java.lang.IllegalStateException: Unknown tag 50 [1.4.182/6]
   at org.h2.mvstore.DataUtils.newIllegalStateException(DataUtils.java:762)
   at org.h2.mvstore.type.ObjectDataType.read(ObjectDataType.java:222)
   at org.h2.mvstore.db.TransactionStore$ArrayType.read(TransactionStore.java:1792)
   at org.h2.mvstore.db.TransactionStore$ArrayType.read(TransactionStore.java:1759)
   at org.h2.mvstore.Page.read(Page.java:843)
   at org.h2.mvstore.Page.read(Page.java:230)
   at org.h2.mvstore.MVStore.readPage(MVStore.java:1813)
   at org.h2.mvstore.MVMap.readPage(MVMap.java:769)
   at org.h2.mvstore.Page.getChildPage(Page.java:252)
   at org.h2.mvstore.MVMap.getFirstLast(MVMap.java:351)
   at org.h2.mvstore.MVMap.firstKey(MVMap.java:218)
   at org.h2.mvstore.db.TransactionStore.init(TransactionStore.java:169)
   at org.h2.mvstore.db.TransactionStore.<init>(TransactionStore.java:117)
   at org.h2.mvstore.db.TransactionStore.<init>(TransactionStore.java:81)
   at org.h2.tools.Recover.dumpMVStoreFile(Recover.java:593)
   at org.h2.tools.Recover.process(Recover.java:331)
   at org.h2.tools.Recover.runTool(Recover.java:192)
   at org.h2.tools.Recover.main(Recover.java:155)

I also noticed that two another files (.txt and .sql) has been created but they don't seem to contain a data.

Answer 1

I got the same situation last week with JIRA database, it took me few hours to do google regarding to this problem however, there are no answers which can resolve the situation.

I decided to take a look at H2 source code and I can recover the whole database with very simple code. I may not understand whole picture about the situation e.g. root cause, in which condition it happened, etc. However, the cause is: when you connect to h2 file then H2 engine will look into auditLog and rollback the in-progress transactions, there are some data which have unknown type (id is 17) and H2 fails to rollback due to exception during recognize the type (id 17).

My code is simple, add h2 lib into your build path then just manual connect to file and clear auditLog because I think it is just the log and will not have big impact (someone may correct me). Hopefully, you can resolve your problem as well.

public static void main(final String[] args) {
    // open the store (in-memory if fileName is null)
    final MVStore store = MVStore.open("C:\\temp\\h2db.mv.db");

    final MVMap<Object, Object> openMap = store.openMap("undoLog");

    openMap.clear();

    // close the store (this will persist changes)
    store.close();
}

Answer 2

Another solution for this problem:

1. Go to your home folder (~ in linux).

2. Move all files named [*.mv.db] to a backup with a different name. For example: mv xyz.mv.db xyz.mv.db.backup

3. Restart your database.

This seems to clear out MVStore meta-data used for H2 undo features, and resolves the NPE from the MV Store compare.