搜索特定字段时，elasticsearch中出现错误＃400

Question

我在Elasticsearch中有以下类似内容：

{
"took": 3,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"failed": 0
},
"hits": {
"total": 500948,
"max_score": 1,
"hits": [
{
"_index": "site_index",
"_type": "gene",
"_id": "FB:1346023",
"_score": 1,
"_source": {......

现在，我只对_id感兴趣，我想获得所有包含特定值的_id，即以“ FB”开头的_id。这是我的代码：

http://localhost:9200/site_index/_search?_id: "*.FB:.*

但是，为什么它给我erro 400？