CREATE TABLE IF NOT EXISTS prune_field (
  ts TIMESTAMP TIME INDEX,
  `tag` UInt16,
  a UInt8,
  b UInt8,
PRIMARY KEY (`tag`)) ENGINE = mito WITH('merge_mode'='last_non_null');

Affected Rows: 0

insert into prune_field(ts, `tag`, a, b) values(0, 1, 1, null);

Affected Rows: 1

admin flush_table('prune_field');

+----------------------------------+
| ADMIN flush_table('prune_field') |
+----------------------------------+
| 0                                |
+----------------------------------+

insert into prune_field(ts, `tag`, a, b) values(0, 1, null, 1);

Affected Rows: 1

admin flush_table('prune_field');

+----------------------------------+
| ADMIN flush_table('prune_field') |
+----------------------------------+
| 0                                |
+----------------------------------+

select * from prune_field where a = 1;

+---------------------+-----+---+---+
| ts                  | tag | a | b |
+---------------------+-----+---+---+
| 1970-01-01T00:00:00 | 1   | 1 | 1 |
+---------------------+-----+---+---+

select * from prune_field where b = 1;

+---------------------+-----+---+---+
| ts                  | tag | a | b |
+---------------------+-----+---+---+
| 1970-01-01T00:00:00 | 1   | 1 | 1 |
+---------------------+-----+---+---+

select * from prune_field;

+---------------------+-----+---+---+
| ts                  | tag | a | b |
+---------------------+-----+---+---+
| 1970-01-01T00:00:00 | 1   | 1 | 1 |
+---------------------+-----+---+---+

select * from prune_field where a = 1 and b = 1;

+---------------------+-----+---+---+
| ts                  | tag | a | b |
+---------------------+-----+---+---+
| 1970-01-01T00:00:00 | 1   | 1 | 1 |
+---------------------+-----+---+---+

drop table prune_field;

Affected Rows: 0