📝Utilising CirclesQuery Class

The CirclesQuery class allows you to execute custom queries against the Circles RPC api.

The previously shown CirclesData class returns CirclesQuery<T> objects for all paged query results. You can execute custom queries against all tables in the Circles index and filter with them.

Write a query

First you'll need to define a query. The basic structure of a query is the same as for a basic SQL select. It has the following fields:

• namespace: Used to distinguish between tables and views as well and to tell the tables of the two Circles version apart from each other.

• table: The name of the table you want to query.

• columns: A list of column names you want to select.

• filter: A list of filter conditions that must be met.

• sortOrder: Can be 'asc' or 'desc'.

• limit: How many rows to return (max: 1000).

Check out the documentation of the circles_query rpc method for a list of tables.

Here is a query that reads all avatars with type group. Other avatar types you can try are human and organization.

const queryDefinition: PagedQueryParams = {
  namespace: 'V_Crc',
  table: 'Avatars',
  columns: [
    'blockNumber',
    'transactionIndex',
    'logIndex',
    'avatar',
    'name',
    'cidV0Digest'
  ],
  filter: [
    {
      Type: 'FilterPredicate',
      FilterType: 'Equals',
      Column: 'type',
      Value: 'group'
    }
  ],
  sortOrder: 'ASC',
  limit: 100
};

If you want to be able to load the next page (queryNextPage()) you must always include the following fields in your query:blockNumber, transactionIndex, logIndex.

Define a row type

You can define a type for the rows of your query, or just go with any if the type doesn't matter.

If you want to specify a custom type, it must extend the EventRow type. The EventRow type contains the blockNumber, transactionIndex and logIndex fields which are required for pagination.

interface MyGroupType extends EventRow {
  avatar: string;
  name: string;
  cidV0Digest?: string;
}

Execute the query

To execute the query definition, you'll need a CirclesRpc instance. Create one and pass the Circles rpc url to the constructor.

const circlesRpc = new CirclesRpc('https://chiado-rpc.aboutcircles.com');

Then create a CirclesQuery<MyGroupType> instance.

const query = new CirclesQuery<MyGroupType>(circlesRpc, queryDefinition);

Call getNextPage() to retrieve the first page of the result set. You can then access the results through the currentPage property. This property includes the results themselves, along with firstCursor, lastCursor, limit, size, and sortOrder.

const hasResults = await query.queryNextPage();
if (!hasResults) {
  console.log("The query yielded no results.");
} else {
  const rows = query.currentPage.results;
  rows.forEach(row => console.log(row));
}

Add computed columns

You can extend the CirclesQuery with computed columns. Computed columns are defined by a callback that takes in the row and returns a new value. Here we convert the value of the previously queried cidV0Digest field (which is originally a hex-string) to a CID in Qm.. format.

const calculatedColumns = [{
  name: 'cidV0',
  generator: async (row: MyGroupType) => {
    if (!row.cidV0Digest) {
      return undefined;
    }

    const dataFromHexString = hexStringToUint8Array(row.cidV0Digest.substring(2));
    return uint8ArrayToCidV0(dataFromHexString);
  }
}];

The new column should be added to the custom type.

interface MyGroupType extends EventRow {
  avatar: string;
  name: string;
  cidV0Digest?: string;
  cidV0?: string
}

Then you can execute the query just like you did before. The calculated column function will be executed for each row in a page.

const query = new CirclesQuery<MyGroupType>(circlesRpc, queryDefinition, calculatedColumns);

const hasResults = await query.queryNextPage();
if (!hasResults) {
  console.log("The query yielded no results.");
} else {
  const rows = query.currentPage.results;
  rows.forEach(row => console.log(row));
}