Question

N1QL中是否有内置函数，相当于MySQL中SQL_CALC_FOUND_ROWS和FOUND_ROWS()与LIMIT，OFFSET一起用于准备寻呼机目的？

如果没有什么是获得相同结果的最佳解决方法，而不是执行下面提到的其他N1QL查询

SELECT COUNT(id) FROM mybucket WHERE <same condition that get first result set>

Answer 1

在我们对数据进行排序（因此我们可以计算）和LIMIT结果集的情况下，您可以获得完整可能结果集的计数。 sortCount是没有限制的可能文档的总数。

select * from `beer-sample` where city > "" order by city limit 10;
...
    "status": "success",
    "metrics": {
        "elapsedTime": "273.677801ms",
        "executionTime": "273.636223ms",
        "resultCount": 10,
        "resultSize": 8740,
        **"sortCount": 1390**
    }
}

如果没有ORDER BY，您只需获得以下内容。

select * from `beer-sample` where city > ""  limit 10;
...
    "status": "success",
    "metrics": {
        "elapsedTime": "21.661524ms",
        "executionTime": "21.619021ms",
        "resultCount": 10,
        "resultSize": 10163
    }
}

在4.5中，当您进行覆盖索引扫描时，您可以发出并行查询以仅从索引扫描进行计数。
解释将指示此“CountScan”方法是否可用于查询。

示例：

cbq> explain select count(1) from `beer-sample` where city = 'San Francisco';
{
    "requestID": "fe9b3f0f-bfc2-4132-bfd7-6268b78860d4",
    "signature": "json",
    "results": [
        {
            "plan": {
                "#operator": "Sequence",
                "~children": [
                    {
                        **"#operator": "IndexCountScan",**
                        "covers": [
                            "cover ((`beer-sample`.`city`))",
                            "cover ((meta(`beer-sample`).`id`))"
                        ],
                        "index": "idxcity",
                        "index_id": "66d88e11a6178a04",
                        "keyspace": "beer-sample",
                        "namespace": "default",
                        "spans": [
                            {
                                "Range": {
                                    "High": [
                                        "\"San Francisco\""
                                    ],
                                    "Inclusion": 3,
                                    "Low": [
                                        "\"San Francisco\""
                                    ]
                                }
                            }
                        ],
                        "using": "gsi"
                    },
                    {
                        "#operator": "IndexCountProject",
                        "result_terms": [
                            {
                                "expr": "count(1)"
                            }
                        ]
                    }
                ]
            },
            "text": "select count(1) from `beer-sample` where city = 'San Francisco'"
        }
    ],
    "status": "success",
    "metrics": {
        "elapsedTime": "4.434551ms",
        "executionTime": "4.382437ms",
        "resultCount": 1,
        "resultSize": 1572
    }
}
cbq>

N1QL＆＃34;镍＆＃34;中的SQL_CALC_FOUND_ROWS / FOUND_ROWS（）相当于什么？ Couchbase

1 个答案: