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MCOL-5603 Online alter can break data consistency

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copy of https://github.com/mariadb-corporation/mariadb-columnstore-engine/pull/3021

Propagate the TL lock to TL_READ_NO_INSERT, blocking any concurrent writes until the end of a copy stage.

After that, this lock will be unlocked, allowing a window to write into a table before MDL is upgraded to exclusive (see online_alter_read_from_binlog call and the "alter_table_online_before_lock" debug syncpoint). This window will be covered by the second replication iteration after the lock upgrade
This commit is contained in:
Leonid Fedorov
2025-05-23 00:31:55 +00:00
committed by Aleksei Bukhalov
parent e202f4b076
commit b9064ca925
1 changed files with 5 additions and 1 deletions
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6
dbcon/mysql/ha_mcs.cpp
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@@ -930,7 +930,7 @@ int ha_mcs::external_lock(THD* thd, int lock_type)
get_lock_data() in lock.cc
*/
THR_LOCK_DATA** ha_mcs::store_lock(THD* /*thd*/, THR_LOCK_DATA** to, enum thr_lock_type /*lock_type*/)
THR_LOCK_DATA** ha_mcs::store_lock(THD* thd, THR_LOCK_DATA** to, enum thr_lock_type lock_type)
{
// if (lock_type != TL_IGNORE && lock.type == TL_UNLOCK)
// lock.type=lock_type;
@@ -938,6 +938,10 @@ THR_LOCK_DATA** ha_mcs::store_lock(THD* /*thd*/, THR_LOCK_DATA** to, enum thr_lo
#ifdef INFINIDB_DEBUG
puts("store_lock");
#endif
if (thd_sql_command(thd) == SQLCOM_ALTER_TABLE && thd_tx_isolation(thd) == ISO_REPEATABLE_READ &&
lock_type == TL_READ)
table->reginfo.lock_type = TL_READ_NO_INSERT;
return to;
}