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From Robert Wille <rwi...@fold3.com>
Subject Schema questions for data structures with recently-modified access patterns
Date Tue, 21 Jul 2015 03:59:52 GMT
Data structures that have a recently-modified access pattern seem to be a poor fit for Cassandra.
I’m wondering if any of you smart guys can provide suggestions.

For the sake of discussion, lets assume I have the following tables:

CREATE TABLE document (
	docId UUID,
	doc TEXT,
	last_modified TIMEUUID,
	PRIMARY KEY ((docid))
)

CREATE TABLE doc_by_last_modified (
	date TEXT,
	last_modified TIMEUUID,
	docId UUID,
	PRIMARY KEY ((date), last_modified)
)

When I update a document, I retrieve its last_modified time, delete the current record from
doc_by_last_modified, and add a new one. Unfortunately, if you’d like each document to appear
at most once in the doc_by_last_modified table, then this doesn’t work so well.

Documents can get into the doc_by_last_modified table multiple times if there is concurrent
access, or if there is a consistency issue.

Any thoughts out there on how to efficiently provide recently-modified access to a table?
This problem exists for many types of data structures, not just recently-modified. Any ordered
data structure that can be dynamically reordered suffers from the same problems. As I’ve
been doing schema design, this pattern keeps recurring. A nice way to address this problem
has lots of applications.

Thanks in advance for your thoughts

Robert


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