通过聚合查询获取group by 后的数量
/**
* 获取key的个数
*
* @param key 要group by的字段名
* @param index 索引名称
* @return id的个数
*/
public static int getKeyCount(String key, String index) {
int count = 0;
TransportClient client = null;
try {
client = connectionPool.getConnection();
if (client == null) {
throw new Exception("没有获取到连接!");
}
SearchRequestBuilder search = client.prepareSearch(index);
//cardinality聚合查询,相当于groupby字段名
SearchResponse sr = search.addAggregation(AggregationBuilders.cardinality(key + "_count").field(key)).execute().actionGet();
//从返回数据提取id总数
Cardinality result = sr.getAggregations().get(key + "_count");
long value = result.getValue();
count = (int) value;
} catch (InterruptedException e) {
} catch (Exception e) {
logger.error("getKeyCount错误", e);
} finally {
connectionPool.releaseConnection(client);
}
return count;
}
获取group by后的所有key值
/**
* 获取所有key
*
* @param key 被group by的字段名
* @param index 索引名称
* @return 所有id
*/
public static List<String> getAllKey(String key, String index) {
int keyCount = getKeyCount(key, index);
List<String> strings = new ArrayList<>();
TransportClient client = null;
try {
client = connectionPool.getConnection();
if (client == null) {
throw new Exception("没有获取到数据库连接!");
}
SearchRequestBuilder searchRequestBuilder = client.prepareSearch(index);
//使用聚合,实现去重查询
SearchResponse searchResponse = searchRequestBuilder.
addAggregation(AggregationBuilders.terms("models").field(key).size(keyCount)).execute().actionGet();
Terms term = searchResponse.getAggregations().get("models");
List<? extends Terms.Bucket> buckets = term.getBuckets();
//遍历结果,提取出id
for (Terms.Bucket bucket : buckets) {
String keyAsString = bucket.getKeyAsString();
strings.add(keyAsString);
}
buckets.clear();
} catch (InterruptedException e) {
} catch (Exception e) {
logger.error("getAllKey错误", e);
} finally {
connectionPool.releaseConnection(client);
}
return strings;
}