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I'm currently using the geth implementation. The problem is currently I am tracking erc20 token transfers using purely the erc20 contract event logs and filtering for Transfer event, then saving that in a database with the following basic struct

type Transfer struct {
  To
  From
  TxHash
  BlockHash
}

The problem is that in the geth implementation there is a concerning comment on the log struct at https://github.com/ethereum/go-ethereum/blob/master/core/types/log.go

// Log represents a contract log event. These events are generated by the LOG opcode and
// stored/indexed by the node.
type Log struct {
    // Consensus fields:
    // address of the contract that generated the event
    Address common.Address `json:"address" gencodec:"required"`
    // list of topics provided by the contract.
    Topics []common.Hash `json:"topics" gencodec:"required"`
    // supplied by the contract, usually ABI-encoded
    Data []byte `json:"data" gencodec:"required"`

    // Derived fields. These fields are filled in by the node
    // but not secured by consensus.
    // block in which the transaction was included
    BlockNumber uint64 `json:"blockNumber"`
    // hash of the transaction
    TxHash common.Hash `json:"transactionHash" gencodec:"required"`
    // index of the transaction in the block
    TxIndex uint `json:"transactionIndex"`
    // hash of the block in which the transaction was included
    BlockHash common.Hash `json:"blockHash"`
    // index of the log in the block
    Index uint `json:"logIndex"`

    // The Removed field is true if this log was reverted due to a chain reorganisation.
    // You must pay attention to this field if you receive logs through a filter query.
    Removed bool `json:"removed"`
}

It says that I shouldn't trust the log txHash, BlockNumber since they are not secured by concensus. As a result, I'm looking for another to correctly keep track of all erc20 transfers using a different method. I'm currently thinking of looping through all the txs in a block and checking the receipts for transfer events relating to the specific erc20 contract I'm concerned about. Is this a correct approach? Is there anything I'm missing?

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  • The comment is due to the protocol not providing a cryptographic proof for those fields. Those field could be determined from the transaction execution. To get those fields in a trustlessly manner you need to run your own node. IMHO as long as you trust the node providing that data it should fine to use them.
    – Ismael
    Oct 24, 2022 at 6:27
  • I can have my own node but would those fields be derived from the node that submitted the transaction or from my own node to which I am making API call to filter event logs from a block?
    – bhuynh
    Nov 7, 2022 at 17:13
  • A transaction execution is based on the current ethereum world state. It shouldn't depend on the node that submitted the transaction. A full node current world state could be verified with cryptographic proofs, likewise a transaction execution could be verified.
    – Ismael
    Nov 9, 2022 at 5:36

1 Answer 1

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The most effective way to track all ERC-20 transfers would be using a Subgrpah to index ERC-20 data. This way, you will have all of the ERC-20-related information ready to be queried at any time.

This guide shows you how to develop and deploy a subgraph using Chainstack to do exactly this.

Indexing ERC-20 token balance

The subgraph you deploy following this article indexes every ERC-20 token balance of every address, as well as every transfer.

Subgraphs overall are a super efficient way to index and use this kind of data; you can find more tutorials on how they work and how to use them on the Chainstack docs | Chainstack subgraphs.

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