| License |
BSD License, same as PostgreSQL. |
| Function |
Load Balancing |
Since PGCluster is the synchronous replication of a multi-master,
it can acquire the same value even if it refers to different Cluster DB.
It is very suitable for load balancing for reference system. |
| When the load of an updating process is high, you may use partial replication feature to decentralize the load. |
| Problem Handling |
Cluster server can be set up three or more machines. When
a problem occurs in Cluster DB, loader balancer and a replication server
will be separated from that machine, and continues service using the other
Cluster DBs. |
| Several replication server can be set up. When an problem
occurs at the replication server, Cluster DB automatically changes connection
to the standing-by replication server. |
| When all replication servers stop, Cluster DB operates in
stand-alone mode. There are two modes for stand-alone mode: read only mode
which only permits references, and read write mode, which permits updating. |
| Several loader balancer can be set up, however, they will not have the problem detection and switching over functions that the loader balancer itself has. |
| Recovery |
When the Cluster DBs were started with a recovery option,
it will come back to a replication system after taking the synchronization
to master DB's data. If there are three or more Cluster DBs, a query can
be processed without stopping service during recovery. |
| Replication |
Query-based |
The replication is done in query-based method. |
| COPY |
Since data read from the COPY (FROM) command are also replicated, the backup files which were created by pg_dump can also be replicated. |
| NOW( ) |
When inserting the present time data with a NOW function (ex. the NOW function is contained in the query, or the default value of a table is being set to 'NOW'), that values will also be replicated. The time will be the time of a replication server. |
NEXTVAL( ),
SETVAL( ) |
The sequence operation function (nextval, setval) will be replicated. |
| Serial type |
Since the order of INSERT processing is controlled to become
the same in each Cluster DB, serial type data is synchronized as well. |
| Stored procedure |
The stored procedure accompanied by data update is replicated. |
