Slow query log has Rows_examined: 0 for queries with subquery and degenerate select

create table t1 (id INT);

create table t2 (id INT);

insert into t1(id) select seq from seq_1_to_20;

insert into t2(id) select seq from seq_21_to_40;

select 100 in (select id from t1) AS res;

+------+

| res  |

+------+

|    0 |

+------+

Here, the slow query log shows Rows_examined as 0, although explain plan shows rows as 20 for the subquery

# Time: 250621  0:05:55

# User@Host: bsrikanth[bsrikanth] @ localhost []

# Thread_id: 3  Schema: db1  QC_hit: No

# Query_time: 0.001479  Lock_time: 0.000475  Rows_sent: 1  Rows_examined: 0

# Rows_affected: 0  Bytes_sent: 60

# Pages_accessed: 0  Pages_read: 0  Pages_prefetched: 0  Pages_updated: 0  Old_rows_read: 0

# Pages_read_time: 0.0000  Engine_time: 0.0219

# Full_scan: Yes  Full_join: No  Tmp_table: No  Tmp_table_on_disk: No

# Filesort: No  Filesort_on_disk: No  Merge_passes: 0  Priority_queue: No

#

# explain: id   select_type     table   type    possible_keys   key     key_len ref     rows    r_rows  filtered        r_filtered      Extra

# explain: 1    PRIMARY NULL    NULL    NULL    NULL    NULL    NULL    NULL    NULL    NULL    NULL    No tables used

# explain: 2    SUBQUERY        t1      ALL     NULL    NULL    NULL    NULL    20      20.00   100.00  0.00    Using where

#

select 100 in (select id from t1) AS res from t2;

+------+

| res  |

+------+

|    0 |

|    0 |

|    0 |

|    0 |

|    0 |

|    0 |

|    0 |

|    0 |

|    0 |

|    0 |

|    0 |

|    0 |

|    0 |

|    0 |

|    0 |

|    0 |

|    0 |

|    0 |

|    0 |

|    0 |

+------+

# Time: 250621  0:06:51

# User@Host: bsrikanth[bsrikanth] @ localhost []

# Thread_id: 3  Schema: db1  QC_hit: No

# Query_time: 0.003730  Lock_time: 0.000845  Rows_sent: 20  Rows_examined: 40

# Rows_affected: 0  Bytes_sent: 174

# Pages_accessed: 0  Pages_read: 0  Pages_prefetched: 0  Pages_updated: 0  Old_rows_read: 0

# Pages_read_time: 0.0000  Engine_time: 0.0728

# Tmp_tables: 1  Tmp_disk_tables: 0  Tmp_table_sizes: 1572800

# Full_scan: Yes  Full_join: No  Tmp_table: Yes  Tmp_table_on_disk: No

# Filesort: No  Filesort_on_disk: No  Merge_passes: 0  Priority_queue: No

#

# explain: id   select_type     table   type    possible_keys   key     key_len ref     rows    r_rows  filtered        r_filtered      Extra

# explain: 1    PRIMARY t2      ALL     NULL    NULL    NULL    NULL    20      20.00   100.00  100.00  

# explain: 2    SUBQUERY        t1      ALL     NULL    NULL    NULL    NULL    20      20.00   100.00  0.00    Using where

#

SET timestamp=1750478811;

select 100 in (select id from t1) AS res from t2;