[BEAM-10379] Nulls are not passed to aggregation function in ZetaSQL.

• Type: Task
• Status: Resolved
• Priority: P2
• Resolution: Fixed
• Fix Version/s: 2.34.0
• Component/s: dsl-sql, dsl-sql-zetasql
• Assignee: Benjamin Gonzalez
• Reporter: Yuwei Fu
• Created: 29/Jun/20 21:55
• Updated: 15/Sep/21 18:30
• Resolved: 15/Sep/21 18:30

Description

Performs a bitwise AND operation on expression and returns the result.

Supported Argument Types: INT64
Returned Data Types: INT64

Examples

SELECT BIT_AND(c) as bit_and FROM UNNEST([0xF001, 0x00A1]) as c;

+---------+
| bit_and |
+---------+
| 1       |
+---------+

 

What is expected: should include both Calcite and ZetaSQL dialects.

How to test: unit tests

Reference: https://cloud.google.com/bigquery/docs/reference/standard-sql/aggregate_functions#bit_and

 

Problems: 

After implementation, the current situation is:
1. When table is empty, the result is empty, correct.

2. When table contains only null values, the result is null, correct.

3. When table contains only valid numerical values, the result is as expected, correct.

4. When table contains both valid numerical values and null values, the result should be null (BitAnd(null, val) = null). But it seems all null values have been directly ignored before doing the bit_and operation. Only numerical values are taken into operation, so the result is incorrect.

 
It turns out that on direct runner, NULL will not be passed to CombineFn thus all NULL inputs are ignored. And then if there is any non-null inputs, bit_and will be applied on them only, which leads to a non-null result, which is not correct.

Before figuring out the root cause and proposing a fix, the previous implementation of BIT_AND is reverted.
 

Issue Links

• blocks: BEAM-9514 AssertionError type mismatch from AggregateScanConverter
• blocks: BEAM-10613 Implement BIT_AND for Beam SQL ZetaSQL dialect as CombineFn
• links to: GitHub Pull Request #13062
• links to: GitHub Pull Request #13866