Description:
During the ALTER TABLE ... IMPORT TABLESPACE operation, the trx_id in dd::index remains unchanged. In contrast, the trx_id of the records in the clustered index of the table is set to the "import" transaction ID, while the rollback pointer (rollptr) is assigned a value of 0.
When a transaction with REPEATABLE READ isolation level is initiated before the import and later attempts to read the imported table, the unchanged trx_id in dd::index misleads the system into believing that the index was created prior to the transaction. Consequently, when the system attempts to read data, it encounters records created by a newer transaction, which are not visible to the current read view established prior to the import. This situation leads the system to attempt to access a previous version of the record using an invalid rollptr valued at 0. This poses a significant risk and can result in server crashes.
How to repeat:
Below is a case provided in MTR format.
--source include/have_debug.inc
connect (con1,localhost,root,,);
connection default;
create table t1 (c1 int, c2 int, primary key(c1));
insert into t1 values (1, 100);
insert into t1 values (2, 200);
create table t2 like t1;
create table t3 like t1;
insert into t2 select * from t1;
insert into t3 select * from t1;
SET SESSION debug='+d,skip_dd_table_access_check';
SELECT tbl.name as table_name, idx.* FROM mysql.tables tbl JOIN mysql.indexes idx ON tbl.id = idx.table_id WHERE tbl.name = 't2';
connection con1;
SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ;
start transaction;
select * from t1;
connection default;
ALTER TABLE t2 DISCARD TABLESPACE;
FLUSH TABLES t3 FOR EXPORT;
LET $MYSQLD_DATADIR = `SELECT @@datadir`;
--copy_file $MYSQLD_DATADIR/test/t3.ibd $MYSQLTEST_VARDIR/tmp/t2.ibd
--copy_file $MYSQLD_DATADIR/test/t3.cfg $MYSQLTEST_VARDIR/tmp/t2.cfg
UNLOCK TABLES;
--copy_file $MYSQLTEST_VARDIR/tmp/t2.ibd $MYSQLD_DATADIR/test/t2.ibd
--copy_file $MYSQLTEST_VARDIR/tmp/t2.cfg $MYSQLD_DATADIR/test/t2.cfg
ALTER TABLE t2 IMPORT TABLESPACE;
--remove_file $MYSQLTEST_VARDIR/tmp/t2.ibd
--remove_file $MYSQLTEST_VARDIR/tmp/t2.cfg
SELECT tbl.name as table_name, idx.* FROM mysql.tables tbl JOIN mysql.indexes idx ON tbl.id = idx.table_id WHERE tbl.name = 't2';
connection con1;
select * from t2;
connection default;
disconnect con1;
drop table t1;
drop table t2;
drop table t3;
I encountered an assertion failure when executing the query SELECT * FROM t2;.
The error message was as follows:
[ERROR] [MY-013183] [InnoDB] Assertion failure: trx0rec.ic:95:len < ((ulint)srv_page_size)
I examined the trx_id of the clustered index for table t2 both before and after the import operation, and I found that they remained unchanged.
SELECT tbl.name as table_name, idx.* FROM mysql.tables tbl JOIN mysql.indexes idx ON tbl.id = idx.table_id WHERE tbl.name = 't2';
table_name id table_id name type algorithm is_algorithm_explicit is_visible is_generated hidden ordinal_position comment options se_private_data tablespace_id engine engine_attribute secondary_engine_attribute
t2 290 369 PRIMARY PRIMARY BTREE 0 1 0 0 1 flags=0; id=161;root=4;space_id=7;table_id=1070;trx_id=1563; 12 InnoDB NULL NULL
