[gmaxwell@argonaut src]$ ./bitcoin-cli getblockstats 101
{
  "avgfee": 0,
  "avgfeerate": 0,
  "avgtxsize": 0,
  "blockhash": "00000000b69bd8e4dc60580117617a466d5c76ada85fb7b87e9baea01f9d9984",
  "feerate_percentiles": [
    0,
    0,
    0,
    0,
    0
  ],
  "height": 101,
  "ins": 0,
  "maxfee": 0,
  "maxfeerate": 0,
  "maxtxsize": 0,
  "medianfee": 0,
  "mediantime": 1231657185,
  "mediantxsize": 0,
  "minfee": 0,
  "minfeerate": 0,
  "mintxsize": 0,
  "outs": 1,
  "subsidy": 5000000000,
  "swtotal_size": 0,
  "swtotal_weight": 0,
  "swtxs": 0,
  "time": 1231661741,
  "total_out": 0,
  "total_size": 0,
  "total_weight": 0,
  "totalfee": 0,
  "txs": 1,
  "utxo_increase": 1,
  "utxo_size_inc": 117
}
[gmaxwell@argonaut src]$ ./bitcoin-cli getblockstats 100000
error code: -8
error message:
One or more of the selected stats requires -txindex enabled

Stats that require txindex should always fail if txindex isn't enabled and the stat is requested, and those stats should not be offered by default.

Also, although the help says it will accept a '1. "hash_or_height"     (string or numeric, required) The block hash or height of the target block', that doesn't seem to work regardless of how I quote it.

[gmaxwell@argonaut src]$ ./bitcoin-cli getblockstats "0000000000000000001b98c07fca289e1ca3358aeabdcca9b7f7ba704d83a3d4"
error: Error parsing JSON:0000000000000000001b98c07fca289e1ca3358aeabdcca9b7f7ba704d83a3d4



{
    if (request.fHelp || request.params.size() > 2)
        throw std::runtime_error(
            "getchaintxstats ( nblocks blockhash )\n"
            "\nCompute statistics about the total number and rate of transactions in the chain.\n"
            "\nArguments:\n"
            "1. nblocks      (numeric, optional) Size of the window in number of blocks (default: one month).\n"
            "2. \"blockhash\"  (string, optional) The hash of the block that ends the window.\n"
            "\nResult:\n"
            "{\n"
            "  \"time\": xxxxx,                         (numeric) The timestamp for the final block in the window in UNIX format.\n"
            "  \"txcount\": xxxxx,                      (numeric) The total number of transactions in the chain up to that point.\n"
            "  \"window_final_block_hash\": \"...\",      (string) The hash of the final block in the window.\n"
            "  \"window_block_count\": xxxxx,           (numeric) Size of the window in number of blocks.\n"
            "  \"window_tx_count\": xxxxx,              (numeric) The number of transactions in the window. Only returned if \"window_block_count\" is > 0.\n"
            "  \"window_interval\": xxxxx,              (numeric) The elapsed time in the window in seconds. Only returned if \"window_block_count\" is > 0.\n"
            "  \"txrate\": x.xx,                        (numeric) The average rate of transactions per second in the window. Only returned if \"window_interval\" is > 0.\n"
            "}\n"
            "\nExamples:\n"