GetTransaction should only use TxIndex if -txindex is set #15293

Does it make sense to change the order and avoid locking cs_main or mempool.cs?

Something like:

bool GetTransaction(const uint256& hash, CTransactionRef& txOut, const Consensus::Params& consensusParams, uint256& hashBlock, const CBlockIndex* const block_index)
{
    if (g_txindex) {
        return g_txindex->FindTx(hash, hashBlock, txOut);
    }

    LOCK(cs_main);

    ...

I believe it would require to add some read-write mutex to TxIndex.

@promag Is this still an issue?

Done in #22383, thanks.