strong TEXT有人能告诉我这个elasticsearch错误是什么意思吗？它抛出了一个解释查询192.132.4.43:9200/search/\u search&explain=true

{
    "error": {
        "root_cause": [
            {
                "type": "invalid_type_name_exception",
                "reason": "Document mapping type name can't start with '_', found: [_search&explain=true]"
            }
        ],
        "type": "invalid_type_name_exception",
        "reason": "Document mapping type name can't start with '_', found: [_search&explain=true]"
    },
    "status": 400
}

不带explain的查询工作得很好，但是当我调用explain时，它抛出了这个错误。elasticsearch是6。