[ARROW-4596] [Rust] [DataFusion] Implement COUNT aggregate function

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.14.0
• Component/s: Rust, Rust - DataFusion
• Labels: newbie pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/21137
• Assignee: Luca Palmieri
• Reporter: Andy Grove
• Created: 16/Feb/19 23:19
• Updated: 11/Jan/23 07:35
• Resolved: 01/Apr/19 22:35

Description

Add support for COUNT aggregate function. See SUM function in aggregates.rs for inspiration.

SQL parser should support COUNT(1) and COUNT ( * ) syntax for counting rows as well as COUNT(column_name) for counting non-null values for a column.

COUNT(DISTINCT expr) should be handled in a separate issue since it is more complex.

Issue Links

• links to: GitHub Pull Request #4020
• links to: GitHub Pull Request #4036