MySQL:MGR Learning (2): the writing process of Write set (write set)
Write_ set [I]); / / copy byte by byte to buffer uint64 const tmp_str_sz= base64_needed_encoded_length ((uint64) BUFFER_READ_PKE); char * write_set_value= (char *) my_malloc (PSI_NOT_INSTRUMENTED, static_cast (tmp_str_sz), MYF (MY_WME)) / / 13bytes (gdb) p tmp_str_sz $2 = 13 if (! write_set_value) / / memory allocation error {/ * purecov: begin inspected * / log_message (MY_ERROR_LEVEL, "No memory to generate write identification hash"); DBUG_RETURN (1) / * purecov: end * /} if (base64_encode (buff, (size_t) BUFFER_READ_PKE, write_set_value) / / do base64 algorithm {/ * purecov: begin inspected * / log_message (MY_ERROR_LEVEL, "Base64 encoding of the write identification hash failed"); DBUG_RETURN (1) / * purecov: end * /} tcle- > add_write_set (write_set_value); / / finally write write set in base64 format to event} DBUG_RETURN (0);} 3. Get_transaction_write_set function Transaction_write_set* get_transaction_write_set (unsigned long m_thread_id) {DBUG_ENTER ("get_transaction_write_set"); THD * thd= NULL; Transaction_write_set* result_set= NULL Find_thd_with_id find_thd_with_id (m_thread_id, false); thd= Global_THD_manager::get_instance ()-> find_thd (& find_thd_with_id); if (thd) {std::set * write_set= thd- > get_transaction ()-> get_transaction_write_set_ctx ()-> get_write_set (); / / Rpl_transaction_write_set_ctx std::set * get_write_set () Unsigned long write_set_size= write_set- > size (); / / returns the collection size if (write_set_size= = 0) {mysql_mutex_unlock (& thd- > LOCK_thd_data); DBUG_RETURN (NULL) } result_set= (Transaction_write_set*) my_malloc (key_memory_write_set_extraction, sizeof (Transaction_write_set), MYF (0)); / / memory space result_set- > write_set_size= write_set_size is allocated for its Transaction_write_set here / / get size result_set- > write_set= (unsigned long long*) my_malloc (key_memory_write_set_extraction, write_set_size * sizeof (unsigned long long), MYF (0)); / / allocate memory int result_set_index= 0 For (std::set::iterator it= write_set- > begin (); / / copy from set to simple memory it! = write_set- > end (); + + it) {uint64 temp= * it; result_set- > write_ set [result _ set_index++] = temp;} mysql_mutex_unlock (& thd- > LOCK_thd_data);} DBUG_RETURN (result_set);}
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