Error: filtering with tuples or arrays not supported

[sssubik]

Hey,
I have array of Hashes that I want to log in an event so that I can search for the hashes later on. But ethers.js doesn't seem to filter the array of Hashes present.
Solidity code:
event onSubmission(bytes32[] indexed docHash);

NodeJs code:
const filter = await contract.filters.onSubmission(["0x69a013f23c52f5415ae41e64561a6948e08df59904925db53f0df74fd64a3833"]);

I get:
Error: filtering with tuples or arrays not supported (argument="contract.docHash", value=[], code=INVALID_ARGUMENT, version=abi/5.0.1)

Is it possible to search for an array inside a event?

[sssubik]

Hey.. Is it possible to search for a element inside an array logged through indexed event?

[ricmoo]

Oh! Sorry, I don't know how I missed this issue.

You cannot search within an indexed set of an array, but you can search for an exact match.

For example, if you were to log an array [ A, B, C ], you cannot search for items that contains A, but you could search for elements that contain exactly A, B and C.

When a value that is not exactly 32 bytes long is indexed, the entry that is logged to the receipt is the hash of that value. This might still require some fiddling with to find the exact hash you want, and based on the error you posted above, I may not have added support for that yet.

Does that make sense?

[sssubik]

Hey @ricmoo. Yes that does make sense. What should I do then. I checked in web3.js and they also have same issue. Is there a way to find out the txn hash based on the docHash?

[sssubik]

Hey @ricmoo. Does this mean it is only possible to search for hashes if we have all the hashes that was passed to the function. Is it not possible to search by using a single hash?

[ricmoo]

That is correct, for the API you have. You could log multiple indexed hashes, however you are still limited to up to 3 indexed values. And the complexity and has cost would go up.

The other option might be to build something like a bloom filter, which would result in false positives you would need to remove afterward.

Or build an extra service which indexed all events and derives this, and caches it in a database to be queried via some backend.

There are options, but nothing built into Ethereum directly... :s

[sssubik]

Hey @ricmoo
But when I query the blockchain with transaction id, it is able to return all the doc hashes and not just a single hash. Why is it different when I query it with filter?

So, as you are saying I have to have a database consisting of transaction ids and query them to blockchain?

[ricmoo]

You mean you are able to get the full list of docHash from the onSubmission event? I don’t think you should be able to. Or do you mean you can query the contract? Can you give an example transaction hash and the code that can return the full set?

The main thing about this is the indexing. The way indexing works is by creating a bloom filter for each of the indexed fields, which allows efficient searching by filters, but is also why there is an additional cost of 375 gas per log topic. This bloom filter is then stored in the receipt and a receipt root it added in the block header so this can be verified (although, I have never used that feature).

But for items which are not fixed-width, they cannot be included in the bloom filter (since the bloom filter requires fixed-width entries), so the hash is used instead.

Does that make sense? Let me know the code snippet that lets you access all the docHash based on transaction hash too and I’ll look more into it. :)

[ricmoo]

Another option is to emit multiple events per call. Like onSumbission(bytes32 docHash) and emit that for each element in docHashes.

[sssubik]

tx =  await provider.getTransaction("0x42556e7c4d482f4766cbc9f53bad5096611167437b15bc419c05c19b6e57fc14")
      input = await   ethers.utils.defaultAbiCoder.decode(
                        [ 'bytes32[]', 'string[]' ],
                        ethers.utils.hexDataSlice(tx.data, 4)
                    )  

This code gives me the bytes32[] and string[] in decoded form. By the way this is ropsten test net
Also if I use multiple onSubmission events wont the transaction cost increase greatly? I did this to minimize my transaction cost, so that I can timestamp my hashes at a very low cost.

[sssubik]

Hey @ricmoo. Thanks for your hints. I am using your way of emitting onSumbission(bytes32 docHash) by looping through all the docHashes

[ricmoo]

Ah yes. You are not decoding the event data. You are decoding the transaction data. If you look at the receipts for that TX, the events for onSubmission will only be the hash of those docHashes.

However, keep in mind this would fail if another contract submitted a docHash. I could have a contract method that took no parameters, but called your contract with the values A and B. The event would be emitted but the tx.data would contain zero hashes (it would only be my 4-byte selector), but the event would contain the hash(A + B).

Your costs will go up, but if you want the ability to search for a specific docHash, you are asking it to build a more complex index for you, so you would expect it to cost more. That said, I don’t think the cost would be /that/ much more. You will pay an additional 750 gas (ish; I think) per docHash. :)

[sssubik]

However, keep in mind this would fail if another contract submitted a docHash. I could have a contract method that took no parameters, but called your contract with the values A and B. The event would be emitted but the tx.data would contain zero hashes (it would only be my 4-byte selector), but the event would contain the hash(A + B).

I did not get this totally. But I have onlyOwner modifier so that only I can call the function

[sssubik]

Hey @ricmoo . Also how do I search indexed string.
I tried
ethers.utils.sha256("CCHdU3mFEYPpa-CYeDSooeZtYSG-CD9czobepa4a9-CRmVpX3Tegacc")
But I get error invalid arrayify value

[sssubik]

Hey @ricmoo I have indexed the string. When I use web3.utils.sha3 for the indexed string I am able to filter it. But for ethers.utils I dont know what is equivalent to web3.utils.sha3. I tried utils.namehash, hashmessage but to no success.
When I use ethers.utils.sha256. I get invalid arrayify value.
Is there a utils from which I can search the string indexed value in the event?

[ricmoo]

You should be using ethers.utils.id to take the keccak256 of a UTF-8 string. You shouldn’t need to use SHA2-256 for anything related to ABI coding.

See here for more info on the available hashing functions. :)

[ricmoo]

(Also keep in mind if you are using the contract.filters it will hash the string for you, so you should pass in the string unhashed for the filter helpers)

[sssubik]

@ricmoo Hey Thanks for the info. Ya it requires no hashing. Hah! very friendly api