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Quickstart: Key-value database

Data NFTs can store arbitrary key-value pairs on-chain. This opens up their usage for a broad variety of applications, such as comments & ratings, attestations, and privately sharing data (when the value is encrypted).

Let's see how!

Here are the steps:

  1. Setup
  2. Publish data NFT
  3. Add key-value pair to data NFT
  4. Retrieve value from data NFT

1. Setup

From data-nfts-and-datatokens-flow, do:

  • 1. Setup : Prerequisites
  • 1. Setup : Download barge and run services
  • 1. Setup : Install the library from v4 sources

And:

  • 1. Setup : Set envvars

2. Publish data NFT

In the console where you set envvars, do the following.

From data-nfts-and-datatokens-flow, do:

  • 2.1 Create a data NFT

3. Add key-value pair to data NFT

# Key-value pair
key = "fav_color"
value = "blue"

# prep key for setter
key_hash = ocean.web3.keccak(text=key)  # Contract/ERC725 requires keccak256 hash

# prep value for setter
value_hex = value.encode('utf-8').hex()  # set_new_data() needs hex

# set
data_nft.set_new_data(key_hash, value_hex, alice_wallet)

4. Retrieve value from data NFT

value2_hex = data_nft.get_data(key_hash)
value2 = value2_hex.decode('ascii')
print(f"Found that {key} = {value2}")

That's it! Note the simplicity. All data was stored and retrieved from on-chain. We don't need Ocean Provider or Ocean Aquarius for these use cases (though the latter can help for fast querying & retrieval).

We can also encrypt the data. Other quickstarts explore this.

Under the hood, it uses ERC725, which augments ERC721 with a well-defined way to set and get key-value pairs.