Contract Events

What is contract events

Contract events are a way for smart contracts, such as those on the Ethereum blockchain, to communicate action or changes to external entities or systems. They enable the logging of on-chain actions which can be captured and monitored off the blockchain by subscribers. These events are defined in the smart contract code, and they can be emitted during the execution of contract functions to provide information about transactions or changes in state, like token transfers or contract updates. This event-driven architecture facilitates efficient and scalable off-chain processing of blockchain interactions.

The event data in the contract is structured, and we can create a table function to analyze them.

How to create

E.g. If you want to create a table function for ERC20 Transfer event. You can find its event ABI from etherscan

{"anonymous":false,
 "inputs":[
   {"indexed":true,"internalType":"address","name":"from","type":"address"},
   {"indexed":true,"internalType":"address","name":"to","type":"address"},
   {"indexed":false,"internalType":"uint256","name":"amount","type":"uint256"}
  ],
  "name":"Transfer",
  "type":"event"
}

Create a table function for Transfer event named tranfer_erc20:

pragma blockduck_create_contract_event_rpc('tranfer_erc20', '{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"from","type":"address"},{"indexed":true,"internalType":"address","name":"to","type":"address"},{"indexed":false,"internalType":"uint256","name":"amount","type":"uint256"}],"name":"Transfer","type":"event"}');

inputs

Args	Types	Info
suffix	VARCHAR	Table function suffix to identify the specific event
event_abi	VARCHAR	JSON ABI of the event to be monitored

Example

D pragma blockduck_create_contract_event_rpc('tranfer_erc20', '{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"from","type":"address"},{"indexed":true,"internalType":"address","name":"to","type":"address"},{"indexed":false,"internalType":"uint256","name":"amount","type":"uint256"}],"name":"Transfer","type":"event"}');
┌─────────┐
│ Success │
│ boolean │
├─────────┤
│ 0 rows  │
└─────────┘

How to query

After that, table function named eth_contract_event_rpc_tranfer_erc20 already been created. Then you can try to query from it.

Inputs

Args	Types	Info
address	LIST(VARCHAR)	Contract address emitting the event
fromBlock	BigInt	Block number to start scanning from
toBlock	BigInt	Block number to stop scanning at
url	VARCHAR	URL of the Ethereum node

Examples

D set variable eth_url = 'https://eth-mainnet.g.alchemy.com/v2/{API_KEY}';
D select * from eth_contract_event_rpc_tranfer_erc20([]::VARCHAR[], 21104078, 21104078, getvariable('eth_url')) limit 10;
┌──────────────────────┬─────────────┬──────────────────────┬─────────────────────────────────────────┬────────────────────────────────────────────────────────────────────┬──────────────────────────┐
│       address        │ blockNumber │   transactionHash    │                  from                   │                                 to                                 │          amount          │
│       varchar        │    int64    │       varchar        │                 varchar                 │                              varchar                               │          varint          │
├──────────────────────┼─────────────┼──────────────────────┼─────────────────────────────────────────┼────────────────────────────────────────────────────────────────────┼──────────────────────────┤
│ 0xabec00542d141bdd…  │    21104078 │ 0x15b539fdf722615a…  │ 0x000000000000000000000000abd055069a6…  │ 0x000000000000000000000000abec00542d141bddf58649bfe860c6449807237c │ 105836228163203292253    │
│ 0xabec00542d141bdd…  │    21104078 │ 0x15b539fdf722615a…  │ 0x000000000000000000000000abd055069a6…  │ 0x00000000000000000000000060a8ea6005f7db580bc0c9341e7e6275d114e874 │ 10477786588157125933126  │
│ 0xc02aaa39b223fe8d…  │    21104078 │ 0x15b539fdf722615a…  │ 0x0000000000000000000000001f2f10d1c40…  │ 0x000000000000000000000000abd055069a6b04db7d1547f88dd01cf14ff09cfd │ 886249995970281472       │
│ 0xc02aaa39b223fe8d…  │    21104078 │ 0x15b539fdf722615a…  │ 0x00000000000000000000000060a8ea6005f…  │ 0x0000000000000000000000001f2f10d1c40777ae1da742455c65828ff36df387 │ 188832235783192576       │
│ 0xabec00542d141bdd…  │    21104078 │ 0x1bd4d5006a6b321c…  │ 0x00000000000000000000000008903a3be1e…  │ 0x000000000000000000000000abec00542d141bddf58649bfe860c6449807237c │ 9748415873909063929026   │
│ 0xabec00542d141bdd…  │    21104078 │ 0x1bd4d5006a6b321c…  │ 0x00000000000000000000000008903a3be1e…  │ 0x00000000000000000000000060a8ea6005f7db580bc0c9341e7e6275d114e874 │ 965093171516997328973575 │
│ 0xc02aaa39b223fe8d…  │    21104078 │ 0x1bd4d5006a6b321c…  │ 0x00000000000000000000000060a8ea6005f…  │ 0x0000000000000000000000003fc91a3afd70395cd496c647d5a6cc9d4b2b7fad │ 14935959444018469899     │
│ 0xc02aaa39b223fe8d…  │    21104078 │ 0x1bd4d5006a6b321c…  │ 0x0000000000000000000000003fc91a3afd7…  │ 0x000000000000000000000000000000fee13a103a10d593b9ae06b3e05f2e7e1c │ 37339898610046174        │
│ 0xc02aaa39b223fe8d…  │    21104078 │ 0xe391af23df899353…  │ 0x000000000000000000000000abd055069a6…  │ 0x0000000000000000000000001f2f10d1c40777ae1da742455c65828ff36df387 │ 910473774728478721       │
│ 0xc02aaa39b223fe8d…  │    21104078 │ 0xe391af23df899353…  │ 0x0000000000000000000000001f2f10d1c40…  │ 0x00000000000000000000000060a8ea6005f7db580bc0c9341e7e6275d114e874 │ 173454427502411776       │
├──────────────────────┴─────────────┴──────────────────────┴─────────────────────────────────────────┴────────────────────────────────────────────────────────────────────┴──────────────────────────┤
│ 10 rows                                                                                                                                                                                   6 columns │
└─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

Dependent RPC Method

• eth_getLogs