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MDEV-23033: All slaves crash once in ~24 hours and loop restart with signal 11

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Problem:
=======
Upon deleting or updating a row in a parent table (with primary key), if
the child table has virtual column and an associated key with ON UPDATE
CASCADE/ON DELETE CASCADE, it will result in slave crash.

Analysis:
========
Tables which are related through foreign key require prelocking similar to
triggers. i.e If a table has triggers/foreign keys we should add all tables
and routines used by them to the prelocking set.  This prelocking happens
during 'open_and_lock_tables' call.  Each table being opened is checked for
foreign key references. If foreign key reference exists then the child
table is opened and it is linked to the table_list. Upon any modification
to  parent table its corresponding child tables are retried from table_list
and they are updated accordingly. This prelocking work fine on master.

On slave  prelocking works for following cases.
 - Statement/mixed based replication
 - In row based replication when trigger execution is enabled through
   'slave_run_triggers_for_rbr=YES/LOGGING/ENFORCE'

Otherwise it results in an assert/crash, as the parent table will not find
the corresponding child table and it will be NULL. Dereferencing NULL
pointer leads to slave server exit.

Fix:
===
Introduce a new 'slave_fk_event_map' flag similar to 'trg_event_map'. This
flag will ensure that when foreign key is enabled in row based replication
all the parent and child tables are prelocked, so that parent is able to
locate the child table.

Note: This issue is specific to slave, hence only slave needs to be
      upgraded.
This commit is contained in:
Sujatha
2020-12-31 18:15:31 +05:30
parent 25db9ffa8b
commit 608b0ee52e
5 changed files with 907 additions and 66 deletions
Download Patch File Download Diff File Expand all files Collapse all files

118
sql/sql_base.cc
View File

@ -4341,6 +4341,70 @@ bool table_already_fk_prelocked(TABLE_LIST *tl, LEX_STRING *db,
return false;
}
/**
Extend the table_list to include foreign tables for prelocking.
@param[in] thd Thread context.
@param[in] prelocking_ctx Prelocking context of the statement.
@param[in] table_list Table list element for table.
@param[in] sp Routine body.
@param[out] need_prelocking Set to TRUE if method detects that prelocking
required, not changed otherwise.
@retval FALSE Success.
@retval TRUE Failure (OOM).
*/
inline bool
prepare_fk_prelocking_list(THD *thd, Query_tables_list *prelocking_ctx,
TABLE_LIST *table_list, bool *need_prelocking,
uint8 op)
{
List <FOREIGN_KEY_INFO> fk_list;
List_iterator<FOREIGN_KEY_INFO> fk_list_it(fk_list);
FOREIGN_KEY_INFO *fk;
Query_arena *arena, backup;
arena= thd->activate_stmt_arena_if_needed(&backup);
table_list->table->file->get_parent_foreign_key_list(thd, &fk_list);
if (thd->is_error())
{
if (arena)
thd->restore_active_arena(arena, &backup);
return TRUE;
}
*need_prelocking= TRUE;
while ((fk= fk_list_it++))
{
// FK_OPTION_RESTRICT and FK_OPTION_NO_ACTION only need read access
static bool can_write[]= { true, false, true, true, false, true };
thr_lock_type lock_type;
if ((op & (1 << TRG_EVENT_DELETE) && can_write[fk->delete_method])
|| (op & (1 << TRG_EVENT_UPDATE) && can_write[fk->update_method]))
lock_type= TL_WRITE_ALLOW_WRITE;
else
lock_type= TL_READ;
if (table_already_fk_prelocked(prelocking_ctx->query_tables,
fk->foreign_db, fk->foreign_table,
lock_type))
continue;
TABLE_LIST *tl= (TABLE_LIST *) thd->alloc(sizeof(TABLE_LIST));
tl->init_one_table_for_prelocking(fk->foreign_db->str, fk->foreign_db->length,
fk->foreign_table->str, fk->foreign_table->length,
NULL, lock_type, false, table_list->belong_to_view,
op, &prelocking_ctx->query_tables_last);
}
if (arena)
thd->restore_active_arena(arena, &backup);
return FALSE;
}
/**
Defines how prelocking algorithm for DML statements should handle table list
@ -4381,55 +4445,21 @@ handle_table(THD *thd, Query_tables_list *prelocking_ctx,
add_tables_and_routines_for_triggers(thd, prelocking_ctx, table_list))
return TRUE;
}
if (table_list->table->file->referenced_by_foreign_key())
{
List <FOREIGN_KEY_INFO> fk_list;
List_iterator<FOREIGN_KEY_INFO> fk_list_it(fk_list);
FOREIGN_KEY_INFO *fk;
Query_arena *arena, backup;
arena= thd->activate_stmt_arena_if_needed(&backup);
table_list->table->file->get_parent_foreign_key_list(thd, &fk_list);
if (thd->is_error())
{
if (arena)
thd->restore_active_arena(arena, &backup);
return TRUE;
}
*need_prelocking= TRUE;
while ((fk= fk_list_it++))
{
// FK_OPTION_RESTRICT and FK_OPTION_NO_ACTION only need read access
static bool can_write[]= { true, false, true, true, false, true };
uint8 op= table_list->trg_event_map;
thr_lock_type lock_type;
if ((op & (1 << TRG_EVENT_DELETE) && can_write[fk->delete_method])
|| (op & (1 << TRG_EVENT_UPDATE) && can_write[fk->update_method]))
lock_type= TL_WRITE_ALLOW_WRITE;
else
lock_type= TL_READ;
if (table_already_fk_prelocked(prelocking_ctx->query_tables,
fk->foreign_db, fk->foreign_table,
lock_type))
continue;
TABLE_LIST *tl= (TABLE_LIST *) thd->alloc(sizeof(TABLE_LIST));
tl->init_one_table_for_prelocking(fk->foreign_db->str, fk->foreign_db->length,
fk->foreign_table->str, fk->foreign_table->length,
NULL, lock_type, false, table_list->belong_to_view,
op, &prelocking_ctx->query_tables_last);
}
if (arena)
thd->restore_active_arena(arena, &backup);
return (prepare_fk_prelocking_list(thd, prelocking_ctx, table_list,
need_prelocking,
table_list->trg_event_map));
}
}
else if (table_list->slave_fk_event_map &&
table_list->table->file->referenced_by_foreign_key())
{
return (prepare_fk_prelocking_list(thd, prelocking_ctx,
table_list, need_prelocking,
table_list->slave_fk_event_map));
}
return FALSE;
}