How to understand the effective point of sql_safe_updates in MySQL
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bool multi_delete_precheck(THD *thd, TABLE_LIST *tables){ SELECT_LEX *select_lex= thd->lex->select_lex; TABLE_LIST *aux_tables= thd->lex->auxiliary_table_list.first; TABLE_LIST **save_query_tables_own_last= thd->lex->query_tables_own_last; DBUG_ENTER("multi_delete_precheck"); /* sql_yacc guarantees that tables and aux_tables are not zero */ DBUG_ASSERT(aux_tables != 0); if (check_table_access(thd, SELECT_ACL, tables, FALSE, UINT_MAX, FALSE)) DBUG_RETURN(TRUE); /* Since aux_tables list is not part of LEX::query_tables list we have to juggle with LEX::query_tables_own_last value to be able call check_table_access() safely. */ thd->lex->query_tables_own_last= 0; if (check_table_access(thd, DELETE_ACL, aux_tables, FALSE, UINT_MAX, FALSE)) { thd->lex->query_tables_own_last= save_query_tables_own_last; DBUG_RETURN(TRUE); } thd->lex->query_tables_own_last= save_query_tables_own_last; if ((thd->variables.option_bits & OPTION_SAFE_UPDATES) && ! select_lex->where_cond()) //Check whether the parameter is enabled and there is no where condition { my_message(ER_UPDATE_WITHOUT_KEY_IN_SAFE_MODE, ER(ER_UPDATE_WITHOUT_KEY_IN_SAFE_MODE), MYF(0));//Error DBUG_RETURN(TRUE); } DBUG_RETURN(FALSE);}
A brief description of the function:
When SQL_SAFE_UPDATES = 1, update and delete statements without where and limit conditions cannot be executed, even update and delete statements with where and limit conditions but without key column cannot be executed.
When SQL_SAFE_UPDATES =0, update and delete operations will execute smoothly.
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