diff options
Diffstat (limited to 'storage/myisammrg/ha_myisammrg.cc')
| -rw-r--r-- | storage/myisammrg/ha_myisammrg.cc | 47 |
1 files changed, 44 insertions, 3 deletions
diff --git a/storage/myisammrg/ha_myisammrg.cc b/storage/myisammrg/ha_myisammrg.cc index ef7cd5712e8..22b4794dbde 100644 --- a/storage/myisammrg/ha_myisammrg.cc +++ b/storage/myisammrg/ha_myisammrg.cc @@ -480,6 +480,31 @@ int ha_myisammrg::add_children_list(void) /* Set the expected table version, to not cause spurious re-prepare. */ child_l->set_table_ref_id(mrg_child_def->get_child_table_ref_type(), mrg_child_def->get_child_def_version()); + /* + For statements which acquire a SNW metadata lock on a parent table and + then later try to upgrade it to an X lock (e.g. ALTER TABLE), SNW + locks should be also taken on the children tables. + + Otherwise we end up in a situation where the thread trying to upgrade SNW + to X lock on the parent also holds a SR metadata lock and a read + thr_lock.c lock on the child. As a result, another thread might be + blocked on the thr_lock.c lock for the child after successfully acquiring + a SR or SW metadata lock on it. If at the same time this second thread + has a shared metadata lock on the parent table or there is some other + thread which has a shared metadata lock on the parent and is waiting for + this second thread, we get a deadlock. This deadlock cannot be properly + detected by the MDL subsystem as part of the waiting happens within + thr_lock.c. By taking SNW locks on the child tables we ensure that any + thread which waits for a thread doing SNW -> X upgrade, does this within + the MDL subsystem and thus potential deadlocks are exposed to the deadlock + detector. + + We don't do the same thing for SNRW locks as this would allow + DDL on implicitly locked underlying tables of a MERGE table. + */ + if (! thd->locked_tables_mode && + parent_l->mdl_request.type == MDL_SHARED_NO_WRITE) + child_l->mdl_request.set_type(MDL_SHARED_NO_WRITE); /* Link TABLE_LIST object into the children list. */ if (this->children_last_l) child_l->prev_global= this->children_last_l; @@ -657,7 +682,7 @@ CPP_UNNAMED_NS_END @return A cloned handler instance. */ -handler *ha_myisammrg::clone(MEM_ROOT *mem_root) +handler *ha_myisammrg::clone(const char *name, MEM_ROOT *mem_root) { MYRG_TABLE *u_table,*newu_table; ha_myisammrg *new_handler= @@ -678,8 +703,8 @@ handler *ha_myisammrg::clone(MEM_ROOT *mem_root) return NULL; } - if (new_handler->ha_open(table, table->s->normalized_path.str, table->db_stat, - HA_OPEN_IGNORE_IF_LOCKED)) + if (new_handler->ha_open(table, name, table->db_stat, + HA_OPEN_IGNORE_IF_LOCKED)) { delete new_handler; return NULL; @@ -1202,6 +1227,22 @@ ha_rows ha_myisammrg::records_in_range(uint inx, key_range *min_key, } +int ha_myisammrg::truncate() +{ + int err= 0; + MYRG_TABLE *table; + DBUG_ENTER("ha_myisammrg::truncate"); + + for (table= file->open_tables; table != file->end_table; table++) + { + if ((err= mi_delete_all_rows(table->table))) + break; + } + + DBUG_RETURN(err); +} + + int ha_myisammrg::info(uint flag) { MYMERGE_INFO mrg_info; |