Mirror provides 3 custom functions which can be in used within transforms to decode raw contract events during processing: _gs_log_decode, _gs_tx_decode and _gs_fetch_abi.

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_gs_log_decode

This function decodes Raw Logs data given a json string representing the ABI string. Since it is stateless it will scale very well across different pipeline sizes. It will automatically use the matching event in the ABI, but partial ABIs that only contain the target event will also work.
Function definition
_gs_log_decode(string abi, string topics, string data)

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Params

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abi
string
required
A string representing a json array of events and functions
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topics
string
required
Name of the column the dataset which contains a string containing the topics, comma separated.
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data
string
required
Name of the column the dataset which contains a string containing the payload of the event.

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Return

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ROW ( event_param TEXT[], event_signature TEXT )
ROW
The function will output a nested ROW type with event_param::TEXT[] and event_signature::TEXT. If you’re planning on using a sink that doesn’t support nested ROWs, you may want to do a further transformation to unnest the result.

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Examples

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Function Call
If you were using the Raw Logs source dataset, you would call this function passing your ABI and using the ‘topics’ and ‘data’ columns. For example:
SELECT
 _gs_log_decode('[
  {
    "anonymous": false,
    "inputs": [
      {
        "indexed": true,
        "name": "src",
        "type": "address"
      },
      {
        "indexed": true,
        "name": "dst",
        "type": "address"
      },
      {
        "indexed": false,
        "name": "wad",
        "type": "uint256"
      }
    ],
    "name": "Transfer",
    "type": "event"
  }
]', `topics`, `data`) as decoded
from base.raw_logs
You would then able to access both topics and data from the decoded column as decoded.event_params and decoded.event_signature in a second transform. See below for a complete example pipeline.

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_gs_tx_decode

This function decodes Raw Traces data given a json string representing the ABI string. Since it is stateless it will scale very well across different pipeline sizes. It will automatically use the matching function in the ABI, but partial ABIs that only contain the target function will also work.
Function definition
_gs_tx_decode(string abi, string input, string output)

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Params

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abi
string
required
A string representing a json array of events and functions
​
input
string
required
Name of the column the dataset which contains a string containing the data sent along with the message call.
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data
string
required
Name of the column the dataset which contains a string containing the data returned by the message call.

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Return

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ROW ( function TEXT, decoded_inputs TEXT[], decoded_outputs TEXT[] )
ROW
The function will output a nested ROW type with the name of the function along with its inputs and outputs as arrays of strings. If you’re planning on using a sink that doesn’t support nested ROWs, you may want to do a further transformation to unnest the result.

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Examples

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Function Call
If you were using the Raw Traces source dataset, you would call this function passing your ABI and using the ‘input’ and ‘output’ columns. For example:
SELECT
 _gs_tx_decode('[
   {
      "inputs": [
        {
          "internalType": "address",
          "name": "sharesSubject",
          "type": "address"
        },
        {
          "internalType": "uint256",
          "name": "amount",
          "type": "uint256"
        }
      ],
      "name": "getBuyPriceAfterFee",
      "outputs": [
        {
          "internalType": "uint256",
          "name": "",
          "type": "uint256"
        }
      ],
      "stateMutability": "view",
      "type": "function"
    }
]', `input`, `output`) as decoded
from base.raw_logs
You would then able to access both function and its inputs and outputs from the decoded columns as decoded.function, decoded.decoded_inputs and decoded.decoded_outputs in a second transform. You can see an example in this guide.

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_gs_fetch_abi

We provide a convenient function for fetching ABIs, as often they are too big to copy and paste into the yaml definition.
The ABI will be fetched once when a pipeline starts. If a pipeline is updated to a new version, or restarted, the ABI will be fetched again. It will not be re-read at any point while a pipeline is running.
Function definition
_gs_fetch_abi(string url, string type)

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Params

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url
string
required
The URL from where the ABI will be fetched
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type
string
required
The type of url. Two types of value are accepted:
  • etherscan for etherscan or etherscan-compatible APIs
  • raw for json array ABIs.
If you use etherscan-compatible APIs it’s highly recommended to include your own API key if you are using this function with a large pipeline. The amount of workers may result in the API limits being surpassed.

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Examples

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Function Call
Following up on the previous example, we can replace the raw ABI definition by a call to basescan using the _gs_log_decode function:
select
    # Call the EVM decoding function
    _gs_log_decode(
        # This fetches the ABI from basescan, a `etherscan` compatible site.
        _gs_fetch_abi('https://api.basescan.org/api?module=contract&action=getabi&address=0xcf205808ed36593aa40a44f10c7f7c2f67d4a4d4', 'etherscan'),
        `topics`,
        `data`
    ) as `decoded`,
from base.raw_logs
In some cases, you may prefer to host the ABI yourself and retrieve it from your a separate server such as Github Gist:
select
    # Call the EVM decoding function
    _gs_log_decode(
        # This fetches the ABI from Github Gist
        _gs_fetch_abi('https://gist.githubusercontent.com/JavierTrujilloG/bde43d5079ea5d03edcc68b4516fd297/raw/7b32cf313cd4810f65e726e531ad065eecc47dc1/friendtech_base.json', 'raw'),
        `topics`,
        `data`
    ) as `decoded`,
from base.raw_logs

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Pipeline Example

Below is an example pipeline definition for decoding events for Friendtech contract in Base, make sure to visit this guide for a more in-depth explanation of this pipeline: 
name: friendtech-decoded-events
apiVersion: 3
sources:
  my_base_raw_logs:
    type: dataset
    dataset_name: base.raw_logs
    version: 1.0.0
transforms:
  friendtech_decoded:
    primary_key: id
    # Fetch the ABI from basescan, then use it to decode from the friendtech address.
    sql: >
      select 
        `id`,
        _gs_log_decode(
            _gs_fetch_abi('https://api.basescan.org/api?module=contract&action=getabi&address=0xcf205808ed36593aa40a44f10c7f7c2f67d4a4d4', 'etherscan'), 
            `topics`, 
            `data`
        ) as `decoded`, 
        block_number, 
        transaction_hash 
      from my_base_raw_logs
      where address='0xcf205808ed36593aa40a44f10c7f7c2f67d4a4d4'
  friendtech_clean:
    primary_key: id
    # Clean up the previous transform, unnest the values from the `decoded` object.
    sql: >
      select 
        `id`, 
        decoded.event_params as `event_params`, 
        decoded.event_signature as `event_signature`,
        block_number,
        transaction_hash
      from friendtech_decoded 
      where decoded is not null
sinks:
  friendtech_events:
    secret_name: EXAMPLE_SECRET
    type: postgres
    from: friendtech_clean
    schema: decoded_events
    table: friendtech