rvnqueryd

1. What is rvnquery?

rvnquery is a Turing complete query language for building immutable API on Ravencoin.

rvnquery is a portable, self-contained, and programmable query language that lets you:

1. Query ravencoin (via rvndb) using a mongodb query language
2. Process the result using jq, a turing complete functional programming language
3. All within a single self-contained declarative query language.

Top level attributes:

• v: version
• q: query (MongoDB query)
• r: response handler (powered by jq)

Learn more here: https://docs.bitdb.network

With this combination, you can create your own custom API that's:

• portable: written in JSON, it's natively supported by all devices, OS, programming languages, and databases.
• self-contained: since the processing function can transform the query result into any format, the query can act as a high level API.
• programmable: combine with other queries to build apps that talk to one another based on ravencoin state

2. Build your own API from Ravencoin!

Here's a simple rvnquery (You can learn more about the syntax here)

{
  "v": 3,
  "q": {
    "find": { "out.h1": "6d0c" },
    "project": { "out.$": 1 }
  }
}

When you send the query to a rvndb node, it will respond with the following result:

Already super useful, but it's still raw because every item in the response is a full transaction.

We can go further by adding a processing step:

{
  "v": 3,
  "q": {
    "find": { "out.h1": "6d0c" },
    "project": {
      "out.$": 1
    }
  },
  "r": {
    "f": "[ [ .[] | .out[0] ] | group_by(.s2)[] | { topic: .[0].s2, messages: [ .[] | .s3 ] } ]"
  }
}

The "r.f" is written in jq, a Turing complete data processing language.

Thanks to this additional step, this will respond with:

To summarize, with rvnquery:

1. Flexible Query: You can write a portable JSON query to read from the blockchain.
2. Response Processing: You can also add additional step to represent the processing logic, which will return your own custom immutable stream of data from ravencoin, or also known as API.
3. Interoperable: When you mix and match these APIs together, you can create applications that trigger and talk to one another in a deterministic manner.

rvnqueryd

1. What is rvnqueryd?

rvnqueryd is a query engine that:

1. Connects to a rvndb node and
2. Let you interact with rvndb using the rvnquery language.

2. prerequisites

rvnqueryd is a query engine that directly interfaces with a RvnDB node. You must have direct access to a RvnDB node through either a local or remote MongoDB URL. (An HTTP based module to come soon)

This library is for connecting directly to a RvnDB MongoDB instance through mongodb:// url and is not for HTTP access. If you're looking for a public HTTP endpoint, this library is not what you're looking for. You can instead use the HTTP-based API endpoint at rvndb.ravencoin.online, which takes only a couple of minutes to get your app up and running.

3. install

npm install --save rvnqueryd

4. usage

First initialize, and use the returned db object to make the query.

A. Using Promises

var rvnqueryd = require('rvnqueryd')
var bql = {
  "v": 3,
  "q": {
    "find": { "out.h1": "6d02" },
    "limit": 50
  },
  "r": {
    "f": "[.[] | .out[0] | {h1: .h1, s2: .s2} ]"
  }
}
rvnqueryd.init().then(function(db) {
  db.read(bql).then(function(response) {
    console.log("Response = ", response)
  })
})

B. Using Async-Await

var rvnqueryd = require('rvnqueryd')
var bql = {
  "v": 3,
  "q": {
    "find": { "out.h1": "6d02" },
    "limit": 50
  },
  "r": {
    "f": "[.[] | .out[0] | {h1: .h1, s2: .s2} ]"
  }
};
(async function () {
  let db = await rvnqueryd.init();
  let response = await db.read(bql);
  console.log("Response = ", response)
})();

Note: By default rvnquery connects to mongodb://localhost:27017 so you don't need to configure anything if you set up RvnDB without changing anything.

5. configuration

You can set the following two options:

1. url: RvnDB Node URL
2. timeout: Request timeout

A. url

Select the RvnDB URL to connect to.

rvnqueryd.init({
  url: "mongodb://localhost:27017"
}).then(function(db) {
  ...
})

B. timeout

Set request timeout in milliseconds. All RvnDB requests will time out after this duration.

rvnqueryd.init({
  timeout: 20000
}).then(function(db) {
  ...
})