FLUSH RAMCHUNK rtindex

FLUSH RAMCHUNK forcibly creates a new disk chunk in an RT table.

Normally, RT table would flush and convert the contents of the RAM chunk into a new disk chunk automatically, once the RAM chunk reaches the maximum allowed rt_mem_limit size. However, for debugging and testing it might be useful to forcibly create a new disk chunk, and FLUSH RAMCHUNK statement does exactly that.

Note that using FLUSH RAMCHUNK increases RT table fragmentation. Most likely, you want to use FLUSH TABLE instead. We suggest that you abstain from using just this statement unless you're absolutely sure what you're doing. As the right way is to issue FLUSH RAMCHUNK with following OPTIMIZE command. Such combo allows to keep RT table fragmentation on minimum.

FLUSH TABLE rtindex

FLUSH TABLE forcibly flushes RT table RAM chunk contents to disk.

Backing up an RT table is as simple as copying over its data files, followed by the binary log. However, recovering from that backup means that all the transactions in the log since the last successful RAM chunk write would need to be replayed. Those writes normally happen either on a clean shutdown, or periodically with a (big enough!) interval between writes specified in rt_flush_period directive. So such a backup made at an arbitrary point in time just might end up with way too much binary log data to replay.

FLUSH TABLE forcibly writes the RAM chunk contents to disk, and also causes the subsequent cleanup of (now redundant) binary log files. Thus, recovering from a backup made just after FLUSH TABLE should be almost instant.