But I do think there is nothing wrong with partitioner-per-namespace. It should be straightfoward to implement (once we have real namespace support to begin with) and it might be interesting for some apps to have that ability.
-Jonathan On Mon, Mar 30, 2009 at 1:26 PM, Jonathan Ellis <jbel...@gmail.com> wrote: > The problem is you're using table to mean something that does not fit > into Cassandra. > > Cassandra has ColumnFamilies but we do not need tables to group those > the way relational databases group columns. > > To the degree that we need locality groups we have Super CFs. > > Cassandra already has (the beginnings of) something called a Table > that is really what you are asking for in the first part, a namespace. > > Probably we should rename that to Schema or Namespace to avoid confusion. > > Have you read the BigTable paper yet? A lot of it does not apply to > Cassandra but the ColumnFamily/Memtable/SSTable descriptions are worth > reading. Sections 4, 5.3, 5.4 in particular. From what I can tell > Cassandra's implementation was heavily inspired by this. > > -Jonathan > > On Mon, Mar 30, 2009 at 1:16 PM, Neophytos Demetriou > <neophy...@gmail.com> wrote: >> I am not sure yet if this is a good idea or not but we might want to >> consider partitions on a per-namespace basis, e.g. prefixing row keys >> with predefined namespaces. I understand that this might not be the >> preferred course of action for those of you using one cassandra cluster >> per application (SLAs, etc) but nothing prevents you from running a >> partitioner per cluster under this scheme. >> >> Here's how this could work: >> >> In storage-conf.xml: >> >> <partitioner ns="mynsp0">RandomPartitioner"</partitioner> >> <partitioner ns="mynsp1">OrderPreservingPartitioner"</paritioner> >> >> The row key would then be of the form "mynamespace:mykey" (namespace >> would be optional). If no namespace is provided then the default >> partitioner is used. In this way we could support ranges for those keys >> that their namespace's partitioner supports it. Of course, namespaces >> could also be used for other purposes. >> >> I have discussed this with a friend who encouraged me to post here. I >> hope I'm not way off with this one. >> >> An alternative is to get multiple tables working and implement per-table >> partitioner support. I think there is a conceptual distinction between >> the two in the sense that a table would most likely be a grouping of >> column families whereas namespaces could span different tables and, in >> some occasions/applications, one might want to utilize the same column >> families with different namespaces. >> >> Any feedback is greatly appreciated. >> >> - Neophytos >> >
