Skip to main content

​
Block data for EVM

EvmBatchProcessor follows the common squid processor architecture, in which data processing happens within the batch handler, a function repeatedly called on batches of on-chain data. The function takes a single argument called “batch context”. Its structure follows the common batch context layout, with ctx.blocks being an array of BlockData objects containing the data to be processed, aligned at the block level. For EvmBatchProcessor the BlockData interface is defined as follows: 
export type BlockData<F extends FieldSelection = {}> = {
  header: BlockHeader<F>
  transactions: Transaction<F>[]
  logs: Log<F>[]
  traces: Trace<F>[]
  stateDiffs: StateDiff<F>[]
}
```
`F` here is the type of the argument of the [`setFields()`](sdk/reference/processors/evm-batch/field-selection) processor method.

`BlockData.header` contains the block header data. The rest of the fields are iterables containing four kinds of blockchain data. The canonical ordering within each iterable depends on the data kind:
 - `transactions` and `logs` are ordered in the same way as they are within blocks;
 - [`stateDiffs`](sdk/reference/processors/evm-batch/state-diffs) follow the order of transactions that gave rise to them;
 - `traces` are ordered in a deterministic but otherwise unspecified way.

The exact fields available in each data item type are inferred from the `setFields()` call argument. They are documented on the [field selection](sdk/reference/processors/evm-batch/field-selection) page:
 - [transactions section](sdk/reference/processors/evm-batch/field-selection/#transactions);
 - [logs section](sdk/reference/processors/evm-batch/field-selection/#logs);
 - [traces section](sdk/reference/processors/evm-batch/field-selection/#traces);
 - [state diffs section](sdk/reference/processors/evm-batch/field-selection/#state-diffs);
 - [block header section](sdk/reference/processors/evm-batch/field-selection/#block-headers).

## Example

The handler below simply outputs all the log items emitted by the contract `0x2E645469f354BB4F5c8a05B3b30A929361cf77eC` in [real time](sdk/resources/unfinalized-blocks):

```typescript
import \{ TypeormDatabase \} from '@subsquid/typeorm-store'
import \{ EvmBatchProcessor \} from '@subsquid/evm-processor'

const CONTRACT_ADDRESS = '0x2E645469f354BB4F5c8a05B3b30A929361cf77eC'.toLowerCase()

const processor = new EvmBatchProcessor()
  .setPortal('https://portal.sqd.dev/datasets/ethereum-mainnet')
  .setRpcEndpoint('<my_eth_rpc_url>')
  .setFinalityConfirmation(75)
  .setBlockRange(\{ from: 17000000 \})
  .addLog({
    address: [CONTRACT_ADDRESS]
  })
  .setFields({ // could be omitted: this call does not change the defaults
    log: {
      topics: true,
      data: true
    }
  })

processor.run(new TypeormDatabase(), async (ctx) => {
  for (let c of ctx.blocks) {
    for (let log of c.logs) {
      if (log.address === CONTRACT_ADDRESS) {
        ctx.log.info(log, `Log:`)
      }
    }
  }
})
One can experiment with the setFields() argument and see how the output changes. For more elaborate examples, check EVM Examples.