LOAD DATA FROM MASTER
Sintassi
LOAD DATA FROM MASTER
Spiegazione
Questa funzionalità è deprecata. Si raccomanda di non usarla più. E' soggetta a rimozione in una futura versione di MariaDB.
Poiché l'implementazione corrente di LOAD DATA FROM MASTER e LOAD TABLE FROM MASTER è molto limitata, queste istruzioni sono deprecate nella versione 4.1 di MySQL e superiori. Verrà introdotta una tecnica più avanzata (chiamata "online backup") in una versione futura. Essa avrà il vantaggio aggiuntivo di funzionare con un maggior numero di Storage Engine.
Per MySQL 5.1 e precedenti, la soluzione alternativa raccomandata all'uso di LOAD DATA FROM MASTER e LOAD TABLE FROM MASTER è usare mysqldump o mysqlhotcopy. Quest'ultimo richiede Perl e due moduli Perl (DBI e DBD:mysql), e funziona solo con le tabelle MyISAM e ARCHIVE. Con mysqldump, si creano dump SQL sul master, che si dirigono (o si copiano) al client mysql dello slave. Ha il vantaggio di funzionare con tutti gli Storage Engine, ma può risultare piuttosto lento, perché funziona usando le SELECT.
This statement takes a snapshot of the master and copies it to the slave. It
updates the values of MASTER_LOG_FILE and
MASTER_LOG_POS so that the slave starts replicating from
the correct position. Any table and database exclusion rules specified with the
--replicate-*-do-* and
--replicate-*-ignore-* options are honored.
--replicate-rewrite-db is not taken into account because a
user could use this option to set up a non-unique mapping such as
--replicate-rewrite-db="db1->db3" and
--replicate-rewrite-db="db2->db3", which would confuse the
slave when loading tables from the master.
Use of this statement is subject to the following conditions:
- It works only for MyISAM tables. Attempting to load a non-MyISAM table
results in the following error:
ERROR 1189 (08S01): Net error reading from master - It acquires a global read lock on the master while taking the snapshot, which prevents updates on the master during the load operation.
If you are loading large tables, you might have to increase the values of
net_read_timeout and net_write_timeout on
both the master and slave servers.
See Server System Variables.
Note that LOAD DATA FROM MASTER does not copy any tables
from the mysql database. This makes it easy to have different users and
privileges on the master and the slave.
To use LOAD DATA FROM MASTER, the replication account that
is used to connect to the master must have the RELOAD and
SUPER privileges on the master and the
SELECT privilege for all master tables you want to load.
All master tables for which the user does not have the
SELECT privilege are ignored by
LOAD DATA FROM MASTER. This is because the master hides
them from the user: LOAD DATA FROM MASTER calls
SHOW DATABASES to know the master databases to load, but
SHOW DATABASES returns only databases
for which the user has some privilege. On the slave side, the user that
issues LOAD DATA FROM MASTER must have privileges for
dropping and creating the databases and tables that are copied.
