var map = function(){

    if (this.gscode == "ZTJB"){

        ymd = this.ymd;

        emit("maxymd", ymd);

    }

}

var reduce = function(key, values){

    var maxYmd = values[0];

    for (var i=1; i<values.length; i++){

        if (maxYmd < values[i]){

            maxYmd = values[i];

        }

    }

    return maxYmd;

}

db.getCollection('calcgsdataflash').mapReduce(

    map,

    reduce,

    {out:{inline:1}}

);

vector<string> vMaxDate;

const char *const MAPPER = "function(){"

	"Date = this.Date;"

	"emit('maxDate',Date)"

"}";

const char *const REDUCER = "function(key, values){"

	"var maxDate = values[0];"

	"for (var i=1; i<values.length; i++){"

		"if (maxDate < values[i]){"

			"maxDate = values[i];"

		"}"

	"}"

	"return maxDate;"

"}";

m_mongoDBMgr.MapReduce(MAPPER, REDUCER, vMaxDate);

for (vector<string>::iterator iter = vMaxDate.begin(); iter != vMaxDate.end(); iter++)

{

	Json::Reader reader;

	Json::Value value;

	if (reader.parse((*iter).c_str(), value))

	{

		iMaxDate = value["value"].asInt();

		TLOG_DEBUG("L2Dynamic iMaxDate:" << iMaxDate << endl);

	}

}//maxYmd

bool CMongoDBMgr::MapReduce(const char *const MAPPER, const char *const REDUCER, vector<string> &vData)

{

    TLOG_DEBUG("begin MapReduce" << endl);

    bson_t reply;

    bson_t *command;

    bson_error_t error;

    mongoc_cursor_t *cursor;

    const bson_t *doc;

    bool map_reduce_done = false;

    bool query_done = false;

    const char *out_collection_name = "outCollection";

    mongoc_collection_t *out_collection;

    bson_t find_query = BSON_INITIALIZER;

    //do MapReduce

    command = BCON_NEW (

        "mapReduce",

        BCON_UTF8 (m_sCollection.c_str()),

        "map",

        BCON_CODE (MAPPER),

        "reduce",

        BCON_CODE (REDUCER),

        "out",

        BCON_UTF8 (out_collection_name)

    );

    bool bRet = mongoc_database_command_simple (m_database, command, NULL, &reply, &error);

    map_reduce_done = true;

    if (!bRet)

    {

        TLOG_DEBUG("MapReduce failed:" << error.message << endl);

        goto cleanup;

        return false;

    }

    //do query

    out_collection = mongoc_database_get_collection (m_database, out_collection_name);

    cursor = mongoc_collection_find_with_opts (out_collection, &find_query, NULL, NULL);

    query_done = true;

    while (mongoc_cursor_next (cursor, &doc))

    {

        char *str;

        str = bson_as_json(doc, NULL);

        vData.push_back(str);

    }

    if (mongoc_cursor_error (cursor, &error))

    {

        TLOG_DEBUG("An error occurred:" << error.message << endl);

        goto cleanup;

        return false;

    }

cleanup:

    if (map_reduce_done)

    {

        bson_destroy (&reply);

        bson_destroy (command);

    }

    if (query_done)

    {

        mongoc_cursor_destroy(cursor);

        mongoc_collection_destroy (out_collection);

    }

    return true;

}