[DRILL-6962] Function coalesce returns an Error when none of the columns in coalesce exist in a parquet file

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.13.0
• Fix Version/s: 1.16.0
• Labels: ready-to-commit
• Assignee: Bohdan Kazydub
• Reporter: Bohdan Kazydub
• Reviewer: Vova Vysotskyi
• Created: 10/Jan/19 09:27
• Updated: 03/Apr/19 10:10
• Resolved: 25/Jan/19 16:52

Description

As Drill is schema-free, COALESCE function is expected to return a result and not error out even if none of the columns being referred to exists in files being queried.

Here is an example for 2 columns, `unk_col` and `unk_col2`, which do not exist in the parquet files

select coalesce(unk_col, unk_col2) from dfs.`/tmp/parquetfiles`;
java.lang.IndexOutOfBoundsException: index (0) must be less than size (0)
at org.apache.drill.shaded.guava.com.google.common.base.Preconditions.checkElementIndex(Preconditions.java:1196)

Fragment 1:0

[Error Id: 7b9193fb-289b-4fbf-a52a-2b93b01f0cd0 on dkvm2c:31010] (state=,code=0)

Issue Links

• is related to: DRILL-7041 CompileException happens if a nested coalesce function returns null
• relates to: DRILL-6976 SchemaChangeException happens when using split function in subquery if it returns empty result.
• links to: GitHub Pull Request #1614
• links to: Mailing List discussion