[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



"  \"bip9_softforks\": {           (object) status of BIP9 softforks in progress\n"
            "     \"xxxx\" : {                 (string) name of the softfork\n"
            "        \"status\": \"xxxx\",       (string) one of \"defined\", \"started\", \"locked_in\", \"active\", \"failed\"\n"
            "        \"bit\": xx,              (numeric) the bit (0-28) in the block version field used to signal this softfork (only for \"started\" status)\n"
            "        \"startTime\": xx,        (numeric) the minimum median time past of a block at which the bit gains its meaning\n"
            "        \"timeout\": xx,          (numeric) the median time past of a block at which the deployment is considered failed if not yet locked in\n"
            "        \"since\": xx,            (numeric) height of the first block to which the status applies\n"
            "        \"statistics\": {         (object) numeric statistics about BIP9 signalling for a softfork (only for \"started\" status)\n"
            "           \"period\": xx,        (numeric) the length in blocks of the BIP9 signalling period \n"
            "           \"threshold\": xx,     (numeric) the number of blocks with the version bit set required to activate the feature \n"
            "           \"elapsed\": xx,       (numeric) the number of blocks elapsed since the beginning of the current period \n"
            "           \"count\": xx,         (numeric) the number of blocks with the version bit set in the current period \n"
            "           \"possible\": xx       (boolean) returns false if there are not enough blocks left in this period to pass activation threshold \n"
            "        }\n"
            "     }\n"
            "  }\n"
            "  \"warnings\" : \"...\",           (string) any network and blockchain warnings.\n"
            "}\n"
            "\nExamples:\n"
            + HelpExampleCli("getblockchaininfo", "")
            + HelpExampleRpc("getblockchaininfo", "")
        );
    LOCK(cs_main);
    UniValue obj(UniValue::VOBJ);
    obj.pushKV("chain",                 Params().NetworkIDString());
    obj.pushKV("blocks",                (int)chainActive.Height());
    obj.pushKV("headers",               pindexBestHeader ? pindexBestHeader->nHeight : -1);
    obj.pushKV("bestblockhash",         chainActive.Tip()->GetBlockHash().GetHex());
    obj.pushKV("difficulty",            (double)GetDifficulty(chainActive.Tip()));
    obj.pushKV("mediantime",            (int64_t)chainActive.Tip()->GetMedianTimePast());