Getting gasUsed by specific transaction

[nighostchris]

Currently I am trying to extract all the transactions' details from a specific block.
But seems the field gasUsed is missing from the transactions array that returned by the method provider.getBlockWithTransactions(blockNumber).

{
   difficulty: 3849295379889,
   extraData: '0x476574682f76312e302e312d39383130306634372f6c696e75782f676f312e34',
   gasLimit: { BigNumber: "3141592" },
   gasUsed: { BigNumber: "21000" },
   hash: '0xf93283571ae16dcecbe1816adc126954a739350cd1523a1559eabeae155fbb63',
   miner: '0x909755D480A27911cB7EeeB5edB918fae50883c0',
   nonce: '0x1a455280001cc3f8',
   number: 100004,
   parentHash: '0x73d88d376f6b4d232d70dc950d9515fad3b5aa241937e362fdbfd74d1c901781',
   timestamp: 1439799168,
   transactions: [
     {
       accessList: null,
       blockHash: '0xf93283571ae16dcecbe1816adc126954a739350cd1523a1559eabeae155fbb63',
       blockNumber: 100004,
       chainId: 0,
       confirmations: 12998591,
       creates: null,
       data: '0x',
       from: '0xcf00A85f3826941e7A25BFcF9Aac575d40410852',
       gasLimit: { BigNumber: "90000" },
       gasPrice: { BigNumber: "54588778004" },
       hash: '0x6f12399cc2cb42bed5b267899b08a847552e8c42a64f5eb128c1bcbd1974fb0c',
       nonce: 25,
       r: '0xb23adc880d3735e4389698dddc953fb02f1fa9b57e84d3510a2a4b3597ac2486',
       s: '0x4e856f95c4e2828933246fb4765a5bfd2ca5959840643bef0e80b4e3a243d064',
       to: '0xD9666150A9dA92d9108198a4072970805a8B3428',
       transactionIndex: 0,
       type: 0,
       v: 27,
       value: { BigNumber: "5000000000000000000" },
       wait: [Function]
    }
  ]
}

Is there any convenient way that can achieve my purpose ? Thanks

[ricmoo]

The gasUsed is a property of the transaction receipt, not the transaction. You should be able to use provider.getTransacrionReceipt(hash) to get the amount of gas a transaction consumed during its execution.

[nighostchris]

@ricmoo Thanks for the reply. So basically I need to loop through the transaction hash retrieved from the transactions array above and use getTransactionReceipt for those hashes one by one to get the gasUsed ? If this is the only way then probably I will develop my program in this way.

[ricmoo]

It is the only way I know of.

Depending on the scope of your project, you could investigate syncing a local Geth node and extracting the data from the raw leveldb blocs on disk.

Keep in mind if you are using INFURA or Alchemy, this will gobble up your API key request limit pretty quickly.

Hope this helps. :)