Hands-On Blockchain with Hyperledger

Indexes

Performing queries on large datasets is a computationally complex task. Fabric provides a mechanism for defining indexes on the CouchDB hosted Worldstate to increase efficiency. Note that indexes are also required for sorting operations in queries.

An index is defined in JSON in a separate file with the extension *.json. The full definition of the format is available at: http://docs.couchdb.org/en/2.1.1/api/database/find.html#db-index.

The following snippet illustrates an index that matches our query for the trade agreements we looked at earlier:

 { 
  "index": { 
    "fields": [ 
      "status", 
      "payment" 
    ] 
  }, 
  "name": "index_sp", 
  "type": "json" 
}  

Here, the index files are placed into the folder /META-INF/statedb/couchdb/indexes. During compilation, ...