Paul Rogers created IMPALA-7826:
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Summary: Potential NPE in CatalogOpExecutor
Key: IMPALA-7826
URL: https://issues.apache.org/jira/browse/IMPALA-7826
Project: IMPALA
Issue Type: Bug
Components: Frontend
Affects Versions: Impala 3.0
Reporter: Paul Rogers
{{CatalogOpExecutor}} has two copies of the following:
{code:java}
Db db = catalog_.getDb(dbName);
if (db == null) {
throw new CatalogException("Database: " + db.getName() + " does not
exist.");
}
{code}
If {{db}} is null, we can’t call {{.getName()}} on that object. (The IDE showed
a warning for this which is why my attention was directed to it.) We’ll get a
null pointer exception (NPE) when creating the error message.
IMPALA-7823 includes the obvious fix, change {{db.getName()}} to {{dbName}}.
But, there may be deeper problems:
# Perhaps someone thoughtfully wrapped this call stack in a try/catch block and
used the NPE to infer that the DB was not found.
# Perhaps if-statement is wrong: perhaps the catalog_.getDb() method returns a
Db object even if not found, and the if-statement should be checking for “!
db.isValid()” or some such.
# Perhaps the code is dead: it is simply never called.
# Most likely: perhaps this code is used, but the semantics are such that we
already checked the DB earlier in the flow. The check here is superfluous: it
can never fail. The check, if we had one, should be an assertion.
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