Sun Rui created HIVE-5256:
-----------------------------
Summary: A map join operator may have in-consistent output row
schema with the common join operator which it will replace
Key: HIVE-5256
URL: https://issues.apache.org/jira/browse/HIVE-5256
Project: Hive
Issue Type: Bug
Components: Query Processor
Affects Versions: 0.11.0
Reporter: Sun Rui
When generating a common join operator, Semantic Analyzer gets the input
RowResolver of each parent operators. It then uses the following piece of code
to interate the tables from the RowResolver (refer to
genJoinOperatorChildren()):
RowResolver inputRS = opParseCtx.get(input).getRowResolver();
Iterator<String> keysIter = inputRS.getTableNames().iterator();
...
while (keysIter.hasNext()) {
String key = keysIter.next();
Note that the interation order is not deterministic because of the current
RowResolver implementation:
private HashMap<String, LinkedHashMap<String, ColumnInfo>> rslvMap;
...
public Set<String> getTableNames() {
return rslvMap.keySet();
}
Generally, the interation order has no problem. However, it may be problematic
when a common join operator is being converted to a map join operator.
MapJoinProcessor.convertMapJoin():
RowResolver inputRS =
opParseCtxMap.get(newParentOps.get(pos)).getRowResolver();
List<ExprNodeDesc> values = new ArrayList<ExprNodeDesc>();
Iterator<String> keysIter = inputRS.getTableNames().iterator();
while (keysIter.hasNext()) {
The problem is that the table iteration order for a input RowResolver may be
different from that in the generation of the common join operator, which result
in an in-consistent output row schema. Thus wrong row schema may be input to
child operators and will cause problems.
I found this issue when running a TPC-DS query. And this issue happens to be
exposed due to HIVE-4078.
The proposed fix is to change RowResolver to define rslvMap as LinkedHashMap
instead of HashMap. Thus the table iteration order of a RowResolver is fixed.
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