[jira] [Created] (SPARK-57924) Add bitmap_xor_agg aggregation function

["jiangxintong (Jira)" <ji...@apache.org>]

jiangxintong created SPARK-57924:
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             Summary: Add bitmap_xor_agg aggregation function
                 Key: SPARK-57924
                 URL: https://issues.apache.org/jira/browse/SPARK-57924
             Project: Spark
          Issue Type: Improvement
          Components: SQL
    Affects Versions: 4.2.0
            Reporter: jiangxintong


Introduce bitmap_xor_agg, a bitwise XOR (symmetric difference) aggregation function for flat bitmaps, completing the function set alongside bitmap_or_agg (3.5.0), bitmap_construct_agg (3.5.0), bitmap_count (3.5.0), and bitmap_and_agg (4.1.0, SPARK-53877).

The bitmap_xor_agg function outputs a bitmap representing the bitwise XOR of all bitmaps in the input column. The input column must contain bitmaps generated from bitmap_construct_agg().

{code:sql}
> SELECT substring(hex(bitmap_xor_agg(col)), 0, 6) FROM VALUES (X '10'), (X '30'), (X '40') AS tab(col);
 600000

> SELECT substring(hex(bitmap_xor_agg(col)), 0, 6) FROM VALUES (X '10'), (X '10') AS tab(col);
 000000
{code}

(The second example demonstrates symmetric difference: two identical values XOR to zero.)

h2. Use Cases

Symmetric difference is useful for:
 * Finding users who belong to exactly one of two groups (not both)
 * Detecting changes between two snapshots
 * Any scenario requiring XOR semantics on bitmaps

h2. Implementation

Follow the exact pattern of BitmapAndAgg (SPARK-53877):
 * Merge operation: buffer[i] ^= input[i]
 * Initialize buffer to all zeros (same as BitmapOrAgg)
 * Both update() and merge() paths must use XOR

Relates to: SPARK-53877



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