[CALCITE-3390] ITEM expression does not get pushed to the right input of left-outer-join

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.21.0
• Fix Version/s: 1.22.0
• Component/s: core
• Labels: pull-request-available
• Assignee: Aman Sinha
• Reporter: Aman Sinha
• Created: 07/Oct/19 17:58
• Updated: 06/Mar/20 04:34
• Resolved: 28/Oct/19 08:27

Description

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.

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]]])

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.

Issue Links

• is depended upon by: DRILL-7391 Wrong result when doing left outer join on CSV table
• links to: GitHub Pull Request #1492