Coprocessors: implement propagation constraints
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Key: HBASE-2395
URL: https://issues.apache.org/jira/browse/HBASE-2395
Project: Hadoop HBase
Issue Type: Sub-task
Reporter: Andrew Purtell
Priority: Minor
Some fevered stuff I posted to hbase-dev@:
A coprocessor or coprocessors (which implement RegionObserver) could implement
propagation constraints in a pluggable manner, is one possibility. Coprocessors
also get an ioctl-like interface which could be the channel for attaching
constraints to KVs.
{quote}
First, what about attaching metadata (itself KVs) to KVs in the store, in a way
that it is efficient to look up the metadata for a given KV or set of KVs?
Second, what about the notion of references? For the case above specifically,
metadata on an "inode" KV that consists of a list of pointers to other KVs.
When deleting the "inode" KV -- one that fell off the tail of a stack of
versions -- at compaction time, then the store could follow the pointers and
delete the referenced values also. Or better, decrement a specified Long
encoded KV and then take the delete action on another specified KV (or set of
KVs) if the result <= 0.
So just to be clear I'm not advocating building my use case into HBase -- it is
a motivating example -- but rather there is perhaps some interesting generic
primitives to consider here. They could support mechanisms for referential
integrity that people coming from RDBMS are quite familiar with.
{quote}
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