in-memory tables are silently dropped while close to OOM

[Valentine Gostev]

Created 16 16-Mb HEAP tables, and changed memory limit so free memory remaining was less 10 Mbytes,

Creation and filling of 17th table failed with ERROR 5 (HY000): Out of memory (Needed 128992 bytes) which was expected. After each attempt to create a table there were less memory left. (3 additional attempts were performed)

After that it was found that 3 tables were silently dropped without any notice and mentioning in error log. Amount of memory equal to 3*16Mb was freed by mysqld.

mysql> create table t1 (a VARCHAR (512), b VARCHAR(512)) ENGINE=HEAP;
Query OK, 0 rows affected (0.02 sec)
mysql> insert into t1 values ('348utg93rhbvin3rg38uq589gyu35hgn3o5qg8yu3058uhjbg358goung3q5orgjb3hong35gu093uh8jg034gohuj','nivg3489utg93nj5vui3q5jtg08uj395ugvoi3q5jgi9fhu3qogijvmo3r5buhnuorjgvim3a5kvo5juh935ui');
Query OK, 1 row affected (0.00 sec)
mysql> insert into t1 select * from t1;
...snip...
mysql> insert into t1 select * from t1;
ERROR 1114 (HY000): The table 't1' is full

mysql> create table t2 (a VARCHAR (512), b VARCHAR(512)) ENGINE=HEAP;
Query OK, 0 rows affected (0.03 sec)

mysql> insert into t2 select * from t1;
Query OK, 16121 rows affected (0.06 sec)
Records: 16121 Duplicates: 0 Warnings: 0

...
mysql> create table t16 (a VARCHAR (512), b VARCHAR(512)) ENGINE=HEAP; insert into t16 select * from t1;
Query OK, 0 rows affected (0.02 sec)

Query OK, 16121 rows affected (0.10 sec)
Records: 16121 Duplicates: 0 Warnings: 0

mysql> create table t17 (a VARCHAR (512), b VARCHAR(512)) ENGINE=HEAP; insert into t17 select * from t1;
Query OK, 0 rows affected (0.02 sec)

ERROR 5 (HY000): Out of memory (Needed 128992 bytes)
mysql> drop table t17
    -> ;
Query OK, 0 rows affected (0.00 sec)

mysql> create table t17 (a VARCHAR (512), b VARCHAR(512)) ENGINE=HEAP; insert into t17 select * from t1;
Query OK, 0 rows affected (0.03 sec)

ERROR 5 (HY000): Out of memory (Needed 128992 bytes)
mysql> drop table t17;
Query OK, 0 rows affected (0.00 sec)

mysql> create table t17 (a VARCHAR (512), b VARCHAR(512)) ENGINE=HEAP; insert into t17 select * from t1;
Query OK, 0 rows affected (0.02 sec)

ERROR 5 (HY000): Out of memory (Needed 128992 bytes)
mysql> drop table t17;
Query OK, 0 rows affected (0.00 sec)

mysql> create table t17 (a VARCHAR (512), b VARCHAR(512)) ENGINE=HEAP; insert into t17 select * from t1;
Query OK, 0 rows affected (0.04 sec)

ERROR 5 (HY000): Out of memory (Needed 128992 bytes)
mysql> drop table t17;
Query OK, 0 rows affected (0.00 sec)

mysql> drop table t16,t15.t14;
ERROR 1051 (42S02): Unknown table 't14'
mysql> drop table t16,t15,t14;
ERROR 1051 (42S02): Unknown table 't16'
mysql> drop table t16;
ERROR 1051 (42S02): Unknown table 't16'
mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| t1 |
| t10 |
| t11 |
| t12 |
| t13 |
| t2 |
| t3 |
| t4 |
| t5 |
| t6 |
| t7 |
| t8 |
| t9 |
+----------------+
13 rows in set (0.01 sec)

[Valentine Gostev (longbow)]

invalid, I have dropped tables myself. The typo was in first drop request (point instead of comma) which made me think tables were dropped silently.