Gopal V created HIVE-7232:
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Summary: ReduceSink is emitting NULL keys due to failed keyEval
Key: HIVE-7232
URL: https://issues.apache.org/jira/browse/HIVE-7232
Project: Hive
Issue Type: Bug
Components: Query Processor
Affects Versions: 0.14.0
Reporter: Gopal V
After HIVE-4867 has been merged in, some queries have exhibited a very weird
skew towards NULL keys emitted from the ReduceSinkOperator.
Added extra logging to print expr.column() in ExprNodeColumnEvaluator & in
reduce sink.
{code}
2014-06-14 00:37:19,186 INFO [TezChild]
org.apache.hadoop.hive.ql.exec.ReduceSinkOperator:
numDistributionKeys = 1 {null --> ExprNodeColumnEvaluator(_col10)}
key_row={"reducesinkkey0":442}
{code}
{code}
HiveKey firstKey = toHiveKey(cachedKeys[0], tag, null);
int distKeyLength = firstKey.getDistKeyLength();
if(distKeyLength <= 1) {
StringBuffer x1 = new StringBuffer();
x1.append("numDistributionKeys = "+ numDistributionKeys + "\n");
for (int i = 0; i < numDistributionKeys; i++) {
x1.append(cachedKeys[0][i] + " --> " + keyEval[i] + "\n");
}
x1.append("key_row="+ SerDeUtils.getJSONString(row,
keyObjectInspector));
LOG.info("GOPAL: " + x1.toString());
}
{code}
The query is tpc-h query5, with extra NULL checks just to be sure.
{code}
ELECT n_name,
sum(l_extendedprice * (1 - l_discount)) AS revenue
FROM customer,
orders,
lineitem,
supplier,
nation,
region
WHERE c_custkey = o_custkey
AND l_orderkey = o_orderkey
AND l_suppkey = s_suppkey
AND c_nationkey = s_nationkey
AND s_nationkey = n_nationkey
AND n_regionkey = r_regionkey
AND r_name = 'ASIA'
AND o_orderdate >= '1994-01-01'
AND o_orderdate < '1995-01-01'
and l_orderkey is not null
and c_custkey is not null
and l_suppkey is not null
and c_nationkey is not null
and s_nationkey is not null
and n_regionkey is not null
GROUP BY n_name
ORDER BY revenue DESC;
{code}
The reducer which has the issue has the following plan
{code}
Reducer 3
Reduce Operator Tree:
Join Operator
condition map:
Inner Join 0 to 1
condition expressions:
0 {KEY.reducesinkkey0} {VALUE._col2}
1 {VALUE._col0} {KEY.reducesinkkey0} {VALUE._col3}
outputColumnNames: _col0, _col3, _col10, _col11, _col14
Statistics: Num rows: 183333344 Data size: 95229140992 Basic
stats: COMPLETE Column stats: NONE
Reduce Output Operator
key expressions: _col10 (type: int)
sort order: +
Map-reduce partition columns: _col10 (type: int)
Statistics: Num rows: 183333344 Data size: 95229140992 Basic
stats: COMPLETE Column stats: NONE
value expressions: _col0 (type: int), _col3 (type: int),
_col11 (type: int), _col14 (type: string)
{code}
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