mirror of https://github.com/citusdata/citus.git
d9a9a3263b
In Citus 11.1.0 we changed the order of doing the initial data copy and the replica identity creation when doing a non blocking shard move. This was done to try and increase the speed with which shard moves could be done. But after doing more extensive performance testing this change turned out to have a negative impact on the speed of moves on the setups that I tested. Looking at the resource usage metrics of the VMs the reason for this seems to be that these shard moves were bottlenecked by disk bandwidth. While creating replica identities in bulk after the initial copy will reduce CPU usage a bit, it does require an additional sequence scan of the just written data. So when a VM is bottlenecked on disk, it makes sense to spend a little bit more CPU to avoid an additional scan. Since PKs are usually simple indexes that don't require lots of CPU to update, as opposed to e.g. GiST indexes. This reverts the order change to avoid a regression on shard move speed in these cases. For future releases we might consider re-evaluating our index creation order for other indexes too, and create "simple" indexes before the copy. |
||
|---|---|---|
| .. | ||
| columnar | ||
| distributed | ||
| .gitignore | ||