[
https://issues.apache.org/jira/browse/DRILL-1788?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14245434#comment-14245434
]
Jacques Nadeau commented on DRILL-1788:
---------------------------------------
+1
> 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
> Assignee: Jacques Nadeau
> Fix For: 0.8.0
>
> Attachments:
> 0001-DRILL-1788-Test-query-for-case-insensitive-join.-Fix.patch,
> 0001-Workaround-for-CALCITE-528-Convert-field-names-to-lo.patch
>
>
> 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;
> {code}
> +------------+------------+
> | 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`]]])
> {code}
> But if I change the one of the letters in one of the identifiers to
> uppercase, the rename goes away:
> {code}
> 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`]]])
> {code}
> 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]
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
