Solana: pre/postTokenBalances accountIndex doesnt correspond to accountKeys Index

Error in Solana Transaction: getTransaction Method Issue

As an experienced developer working with Solana blockchain, I’m here to help you troubleshoot and resolve the issue of getting a transaction error in your preTokenBalances account. In this article, we’ll delve into the problem and provide solutions to fix it.

Problem Overview

The error message typically looks like this:

Error: getTransaction method returns invalid pre-token balances

or

Error: AccountIndex mismatch in preTokenBalances account index 2 does not match accountKeyIndex 3

This error occurs when the preTokenBalances account’s accountIndex does not correspond to the expected account key accountKeyIndex.

Causes of the Issue

There are several reasons why this might happen:

• Incorrect account index: Make sure that the accountIndex in your preTokenBalances data is correctly set and matches the expected account index for each account.

• Invalid account keys: Ensure that all accounts in your preTokenBalances have valid account keys. Account keys should be unique for each account, and their indices must match the account key’s order when accessed (e.g., accountIndex 1, accountKeyIndex 0, etc.).

• Incorrect balance data: Verify that your balance data is accurate and up-to-date, as any discrepancies can cause this issue.

Solutions

To resolve this error, follow these steps:

Step 1: Verify account index and key order

Check the following:

• Are all account indices correct (e.g., 2, 3, etc.)?

• Do all account keys match their expected order when accessed (accountKeyIndex 0, accountKeyIndex 1, etc.)?

Step 2: Validate balance data

Double-check your balance data to ensure it is accurate and consistent. This may involve verifying the balances for each account in your preTokenBalances array.

Step 3: Adjust account index values if necessary

If you suspect a mismatch between the accountIndex and accountKeyIndex, update them accordingly:

• For example, if your preTokenBalances array has accounts with indices 2 and 3:

preTokenBalances: [

  {

    accountIndex: 2,

    mint: ...

  },

  {

    accountIndex: 3,

    mint: ...

  }

]

You can then use the corrected accountKeyIndex when accessing these accounts (e.g., using accountKeyIndex 0 or accountKeyIndex 1).

Step 4: Ensure consistency between balances and indices

Verify that your balance data is consistent with its corresponding index. If you have multiple accounts with the same name, ensure that their balances are updated correctly.

Example Use Case

Suppose we have an account with a balance of 1 Solana (SOL) in our preTokenBalances array:

{

  "accountIndex": 2,

  "mint": ...

}

We can update this account’s index and key order as follows:

// Update the account index to match the expected account key order

preTokenBalances[0].accountKeyIndex = 1;


// Verify that the balance data is consistent with its new index

if (preTokenBalances[0].balance == SOL) {

  console.log("Balance updated correctly");

} else {

  console.error("Balance update failed");

}

By following these steps and verifying your account index and key order, you should be able to resolve the getTransaction method error in your Solana transactions.

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