I was wondering if there's plan to support modifiable documents? At
the moment there's patch for Solr (SOLR-139) which enables update to
the indexed documents.
Modifiable documents are really useful for people (like me:)) who
wants to replace DB with searchable document store and at the same
time have UPDATE functionality.
Also, I was wondering how reliable data in ES and how reliable write
operation? For instance, Cassandra claims to be reliable through
"eventually consistent" model (http://www.allthingsdistributed.com/ 2008/12/eventually_consistent.html). What about ES?
Regarding the updates, since elasticsearch provides you with the full JSON document you want, you can always retrieve it, update what you need, and then index it back. ElasticSearch can do that for you, for example, send a JSON document which is an update doc, and ElasticSearch will read the one from the index, merge it for you, and update it back, but for now, you can easily do that yourself. ElasticSearch is different than Solr, since it provides you with the *actual* JSON you indexed.
In terms of reliability, each ElasticSearch operation is atomic, durable, and isolated. An operation is hashed to a specific shard, performed on it, and then replicated to all its replicas. When the operation returns, it has already been replicated to all the replicas and it is "safely" there. Of course, you can configure the number of replicas (in ElasticSearch, reads/search requests work against the replicas as well, so you get read/search scaling with more replicas).
In terms of visibility, ElasticSearch provides near real time visibility, which by default is set to 1 second. This means that when you index something, it will appear in search results and get results at most 1 second after it has been indexed.