Store data into multiple collections

The MongoDB sink can write data to multiple collections.

Change your configuration to use the collectionNames option. This mode is compatible both with the standard mode and with entity mode.

The transform function now works differently:

• For standard mode, put the returned data in a data key and add a collection key, the returned value will look like { data: any, collection: string }
• For entity mode, just add a collection key to the returned object, it should look like { entity: any, collection: string, update: any }

The following example shows an indexer that streams Transfer events and writes them to three separate collections: mints, burns, and transfers.

export default function transform({ events }) {
  return (events ?? []).map(({ event }) => {
    if (isMint(event)) {
      return {
        collection: "mints",
        data: extractMint(event),
      };
    } else if (isBurn(event)) {
      return {
        collection: "burns",
        data: extractBurn(event),
      };
    } else {
      return {
        collection: "transfers",
        data: extractTransfer(event),
      };
    }
  });
}