TestCrashAPI: another NPE

[andreitokar]

20:43:13 22:05:41.604 org.h2.test.synth.TestCrashAPI 20:43:13 seed: 2132477717
ERROR: new TestCrashAPI().init(test).testCase(2132477717); // Bug 717147565 id=-522 callCount=683 openCount=11 General error: "java.lang.NullPointerException"; SQL statement:
drop all objects [50000-198] org.h2.jdbc.JdbcSQLException: General error: "java.lang.NullPointerException"; SQL statement:
drop all objects [50000-198] ------------------------------
org.h2.jdbc.JdbcSQLException: General error: "java.lang.NullPointerException"; SQL statement:
drop all objects [50000-198]
	at org.h2.message.DbException.getJdbcSQLException(DbException.java:394)
	at org.h2.message.DbException.get(DbException.java:171)
	at org.h2.message.DbException.convert(DbException.java:311)
	at org.h2.command.Command.executeUpdate(Command.java:276)
	at org.h2.jdbc.JdbcStatement.executeInternal(JdbcStatement.java:233)
	at org.h2.jdbc.JdbcStatement.execute(JdbcStatement.java:205)
	at org.h2.test.synth.TestCrashAPI.getConnection(TestCrashAPI.java:285)
	at org.h2.test.synth.TestCrashAPI.testCase(TestCrashAPI.java:320)
	at org.h2.test.synth.TestCrashAPI.test(TestCrashAPI.java:187)
	at org.h2.test.synth.TestCrashAPI.main(TestCrashAPI.java:94)
Caused by: java.lang.NullPointerException
	at org.h2.engine.Session.removeLocalTempTable(Session.java:407)
	at org.h2.engine.Database.removeSchemaObject(Database.java:1969)
	at org.h2.table.Table.removeChildrenAndResources(Table.java:554)
	at org.h2.table.TableView.removeChildrenAndResources(TableView.java:446)
	at org.h2.engine.Database.removeSchemaObject(Database.java:2003)
	at org.h2.command.ddl.DropDatabase.dropAllObjects(DropDatabase.java:89)
	at org.h2.command.ddl.DropDatabase.update(DropDatabase.java:38)
	at org.h2.command.CommandContainer.update(CommandContainer.java:103)
	at org.h2.command.Command.executeUpdate(Command.java:263)
	... 6 more

[andreitokar]

And one more:

20:21:15 21:43:44.448 org.h2.test.synth.TestCrashAPI 20:21:15 seed: 1210896404
ERROR: new TestCrashAPI().init(test).testCase(1210896404); // Bug -2096651821 id=-40 callCount=1516 openCount=13 General error: "java.lang.NullPointerException" [50000-198] org.h2.jdbc.JdbcSQLException: General error: "java.lang.NullPointerException" [50000-198] ------------------------------
org.h2.jdbc.JdbcSQLException: General error: "java.lang.NullPointerException" [50000-198]
	at org.h2.message.DbException.getJdbcSQLException(DbException.java:394)
	at org.h2.message.DbException.get(DbException.java:171)
	at org.h2.message.DbException.convert(DbException.java:311)
	at org.h2.message.DbException.toSQLException(DbException.java:283)
	at org.h2.message.TraceObject.logAndConvert(TraceObject.java:365)
	at org.h2.jdbc.JdbcStatement.execute(JdbcStatement.java:207)
	at org.h2.test.synth.TestCrashAPI.getConnection(TestCrashAPI.java:285)
	at org.h2.test.synth.TestCrashAPI.testCase(TestCrashAPI.java:320)
	at org.h2.test.synth.TestCrashAPI.test(TestCrashAPI.java:187)
	at org.h2.test.synth.TestCrashAPI.main(TestCrashAPI.java:94)
Caused by: java.lang.NullPointerException
	at org.h2.command.dml.Query.initExpression(Query.java:531)
	at org.h2.command.dml.Query.initOrder(Query.java:440)
	at org.h2.command.dml.SelectUnion.prepare(SelectUnion.java:360)
	at org.h2.command.Parser.prepareCommand(Parser.java:617)
	at org.h2.engine.Session.prepareLocal(Session.java:616)
	at org.h2.engine.Session.prepareCommand(Session.java:554)
	at org.h2.jdbc.JdbcConnection.prepareCommand(JdbcConnection.java:1246)
	at org.h2.jdbc.JdbcStatement.executeInternal(JdbcStatement.java:217)
	at org.h2.jdbc.JdbcStatement.execute(JdbcStatement.java:205)
	... 4 more

[katzyn]

In first one table cannot be null, so localTempTables was not initialized. It means that addLocalTempTable() was not invoked before. This situation is not expected, but it happened somehow.

In second case there is a compiler warning about possible null dereference. Actually expressionSQL may be null, so null check is required. But I'm not sure that SelectUnion should pass null here. It invokes initOrder() with mustBeInResult = true, but with expressionSQL = null such check cannot work properly, because, unfortunately, H2 compares expressions by their SQL representation that is stored in this list. This may be related with recent changes, before them ORDER_BY_NOT_IN_RESULT was thrown in such situations, but now if expression is a constant or if MySQL-compatibility mode is in use this exception will not be thrown so execution may continue to row 531 that leads to such NPE.

[andreitokar]

In a first case (which BTW is still happening with Travis), this is the only instance of unchecked access to @​​Nullable Session.localTempTables field, so IMHO, plain check is in order.