Is it possible to migrate the indexed data (collections) in SOLR to Elasticsearch (Indices)?
Data volume will be around 100 million to 1 billion. If yes. What should be the approach? Is there any migration tool available which can be leveraged?
Or it has to be reindexed into elasticsearch freshly from the source data?
If is historical data say 1 year and if this data from original source is not available then it looks like we will not be able to get that historical data into elasticsearch. So do we see any other option here?
As there's no SOLR input plugin in Logstash (see Do we have solr input plugin for logstash?), I'd recommend that you write your own script/app which reads the whole content of SOLR indices and send that every x documents as a bulk request to Elasticsearch.