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

[Bohdan Kazydub (JIRA)]

Bohdan Kazydub created DRILL-6962:
-------------------------------------

             Summary: Function coalesce returns an Error when none of the 
columns in coalesce exist in a parquet file
                 Key: DRILL-6962
                 URL: https://issues.apache.org/jira/browse/DRILL-6962
             Project: Apache Drill
          Issue Type: Improvement
            Reporter: Bohdan Kazydub
            Assignee: Bohdan Kazydub


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
{code:java}
select coalesce(unk_col, unk_col2) from dfs.`/tmp/parquetfiles`;
Error: SYSTEM ERROR: CompileException: Line 56, Column 27: Assignment 
conversion not possible from type 
“org.apache.drill.exec.expr.holders.NullableIntHolder” to type 
“org.apache.drill.exec.vector.UntypedNullHolder”

Fragment 1:0

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



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