Steven Phillips created DRILL-1788:
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Summary: Conflicting column names in join
Key: DRILL-1788
URL: https://issues.apache.org/jira/browse/DRILL-1788
Project: Apache Drill
Issue Type: Bug
Reporter: Steven Phillips
Drill doesn't support multiple columns within a batch having the same name.
when doing a join where there are matching column names, the planner will
insert a project to rename one of the columns to avoid this conflict.
However, it appears that there is some case-sensitive matching somewhere in the
code path, because there are some cases where this rewrite does not happen:
For example, this query does do the column name change (see 01-03):
0: jdbc:drill:> explain plan for select n3.n_name from (select n2.n_name from
cp.`tpch/nation.parquet` n1, cp.`tpch/nation.parquet` n2 where n1.n_name =
n2.n_name) n3 join cp.`tpch/nation.parquet` n4 on n3.n_name = n4.n_name;
+------------+------------+
| text | json |
+------------+------------+
| 00-00 Screen
00-01 UnionExchange
01-01 Project(n_name=[$0])
01-02 HashJoin(condition=[=($0, $1)], joinType=[inner])
01-04 HashToRandomExchange(dist0=[[$0]])
02-01 Project(n_name=[$1])
02-02 HashJoin(condition=[=($0, $1)], joinType=[inner])
02-04 HashToRandomExchange(dist0=[[$0]])
04-01 Scan(groupscan=[ParquetGroupScan
[entries=[ReadEntryWithPath [path=/tpch/nation.parquet]],
selectionRoot=/tpch/nation.parquet, numFiles=1, columns=[`n_name`]]])
02-03 Project(n_name0=[$0])
02-05 HashToRandomExchange(dist0=[[$0]])
05-01 Scan(groupscan=[ParquetGroupScan
[entries=[ReadEntryWithPath [path=/tpch/nation.parquet]],
selectionRoot=/tpch/nation.parquet, numFiles=1, columns=[`n_name`]]])
01-03 Project(n_name0=[$0])
01-05 HashToRandomExchange(dist0=[[$0]])
03-01 Scan(groupscan=[ParquetGroupScan
[entries=[ReadEntryWithPath [path=/tpch/nation.parquet]],
selectionRoot=/tpch/nation.parquet, numFiles=1, columns=[`n_name`]]])
But if I change the one of the letters in one of the identifiers to uppercase,
the rename goes away:
0: jdbc:drill:> explain plan for select n3.n_name from (select n2.n_name from
cp.`tpch/nation.parquet` n1, cp.`tpch/nation.parquet` n2 where n1.N_name =
n2.n_name) n3 join cp.`tpch/nation.parquet` n4 on n3.n_name = n4.n_name;
+------------+------------+
| text | json |
+------------+------------+
| 00-00 Screen
00-01 UnionExchange
01-01 Project(n_name=[$0])
01-02 HashJoin(condition=[=($0, $1)], joinType=[inner])
01-04 HashToRandomExchange(dist0=[[$0]])
02-01 Project(n_name=[$1])
02-02 HashJoin(condition=[=($0, $1)], joinType=[inner])
02-04 HashToRandomExchange(dist0=[[$0]])
04-01 Scan(groupscan=[ParquetGroupScan
[entries=[ReadEntryWithPath [path=/tpch/nation.parquet]],
selectionRoot=/tpch/nation.parquet, numFiles=1, columns=[`N_name`]]])
02-03 Project(N_name0=[$0])
02-05 HashToRandomExchange(dist0=[[$0]])
05-01 Scan(groupscan=[ParquetGroupScan
[entries=[ReadEntryWithPath [path=/tpch/nation.parquet]],
selectionRoot=/tpch/nation.parquet, numFiles=1, columns=[`N_name`]]])
01-03 HashToRandomExchange(dist0=[[$0]])
03-01 Scan(groupscan=[ParquetGroupScan [entries=[ReadEntryWithPath
[path=/tpch/nation.parquet]], selectionRoot=/tpch/nation.parquet, numFiles=1,
columns=[`N_name`]]])
Running this query without the rewrite results in failure:
java.lang.IndexOutOfBoundsException: Index: 1, Size: 1
at java.util.ArrayList.rangeCheck(ArrayList.java:604) ~[na:1.7.0_21]
at java.util.ArrayList.get(ArrayList.java:382) ~[na:1.7.0_21]
at
org.apache.drill.exec.record.VectorContainer.getValueAccessorById(VectorContainer.java:252)
~[drill-java-exec-0.7.0-incubating-SNAPSHOT-rebuffed.jar:0.7.0-incubating-SNAPSHOT]
at
org.apache.drill.exec.record.AbstractRecordBatch.getValueAccessorById(AbstractRecordBatch.java:153)
~[drill-java-exec-0.7.0-incubating-SNAPSHOT-rebuffed.jar:0.7.0-incubating-SNAPSHOT]
at
org.apache.drill.exec.test.generated.HashJoinProbeGen249.doSetup(HashJoinProbeTemplate.java:46)
~[na:na]
at
org.apache.drill.exec.test.generated.HashJoinProbeGen249.setupHashJoinProbe(HashJoinProbeTemplate.java:97)
~[na:na]
at
org.apache.drill.exec.physical.impl.join.HashJoinBatch.innerNext(HashJoinBatch.java:226)
~[drill-java-exec-0.7.0-incubating-SNAPSHOT-rebuffed.jar:0.7.0-incubating-SNAPSHOT]
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