zabetak commented on code in PR #5872:
URL: https://github.com/apache/hive/pull/5872#discussion_r2152044245
##########
ql/src/java/org/apache/hadoop/hive/ql/exec/ExplainTask.java:
##########
@@ -1003,6 +1003,9 @@ public JSONObject outputPlan(Object work, PrintStream out,
Operator<? extends OperatorDesc> operator =
(Operator<? extends OperatorDesc>) work;
final int visitCnt = operatorVisits.merge(operator, 1, Integer::sum);
+ if (conf == null && this.work != null && this.work.getFetchTask() !=
null) {
+ conf = this.work.getFetchTask().getConf();
+ }
Review Comment:
The initial NPE may be avoided but it is not guaranteed that
`this.work.getFetchTask().getConf()` will be not null so technically the code
could still hit NPE. Furthermore, I see at least 9 references to `conf` inside
this class that do not account for the nullability of the field so fixing one
of those seems somewhat incomplete.
Moreover, this kind of fallback strategy to obtain a conf object from the
internal fetch task else does not seem to be a widespread pattern so not sure
what's the reasoning behind it.
Since the problem seems to be triggered mainly by `HiveProtoLoggingHook` I
was wondering if we should rather ensure that the respective class passes a
non-null configuration object even if that is the default one (`new
HiveConf()`).
Another alternative would be to do something like the following:
```java
final int limit = conf == null ?
ConfVars.HIVE_EXPLAIN_NODE_VISIT_LIMIT.defaultIntVal
: conf.getIntVar(ConfVars.HIVE_EXPLAIN_NODE_VISIT_LIMIT);
```
that definitely prevents the NPE no matter what, but it is still a localized
fix.
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