[
https://issues.apache.org/jira/browse/CALCITE-3390?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16946179#comment-16946179
]
Julian Hyde commented on CALCITE-3390:
--------------------------------------
Yes, ITEM should be declared as "strong", in the sense that {{x[y]}} is null if
{{x}} is null. But we don't have "only if"; I don't recall whether we need
"only if" to safely push through outer joins.
> ITEM expression does not get pushed to the right input of left-outer-join
> -------------------------------------------------------------------------
>
> Key: CALCITE-3390
> URL: https://issues.apache.org/jira/browse/CALCITE-3390
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.21.0
> Reporter: Aman Sinha
> Assignee: Aman Sinha
> Priority: Major
>
> In the following query, the ITEM expression above the Left Outer Join does
> not get pushed to the right input (null-preserving input) of the join whereas
> it should since ITEM does not change the nullability.
> {noformat}
> explain plan without implementation for select tt7.columns[0], tt8.columns[0]
> as x from tt7 left outer join tt8 on tt7.columns[0] = tt8.columns[0];
> DrillScreenRel
> DrillProjectRel(EXPR$0=[$1], x=[ITEM($2, 0)])
> DrillJoinRel(condition=[=($0, $3)], joinType=[left])
> DrillProjectRel($f2=[ITEM($0, 0)], ITEM=[ITEM($0, 0)])
> DrillScanRel(table=[[dfs, tmp, tt7]], groupscan=[EasyGroupScan
> [selectionRoot=file:/tmp/tt7, numFiles=1, columns=[`columns`[0]],
> files=[file:/tmp/tt7/0_0_0.csv]]])
> DrillProjectRel(columns=[$0], $f2=[ITEM($0, 0)])
> DrillScanRel(table=[[dfs, tmp, tt8]], groupscan=[EasyGroupScan
> [selectionRoot=file:/tmp/tt8, numFiles=1, columns=[`columns`, `columns`[0]],
> files=[file:/tmp/tt8/0_0_0.csv]]])
> {noformat}
> From what I can tell, the change in behavior occurred with CALCITE-1753;
> before that the ITEM was pushed on both sides of the Left Outer Join.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
