salim achouche created DRILL-6101:
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Summary: Optimize Implicit Columns Processing
Key: DRILL-6101
URL: https://issues.apache.org/jira/browse/DRILL-6101
Project: Apache Drill
Issue Type: Improvement
Components: Execution - Relational Operators
Reporter: salim achouche
Assignee: salim achouche
Problem Description -
* Apache Drill allows users to specify columns even for SELECT STAR queries
* From my discussion with [~paul-rogers], Apache Calcite has a limitation
where the, extra columns are not provided
* The workaround has been to always include all implicit columns for SELECT
STAR queries
* Unfortunately, the current implementation is very inefficient as implicit
column values get duplicated; this leads to substantial performance degradation
when the number of rows are large
Suggested Optimization -
* The NullableVarChar vector should be enhanced to efficiently store duplicate
values
* This will not only address the current Calcite limitations (for SELECT STAR
queries) but also optimize all queries with implicit columns
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