Question

我有一个名为search2的集合，大约有20000个这样的文档：

    {
        "loc": {
        "type": "Polygon",
        "coordinates": [
            [
            [
                43.78526674007639,
                11.14739998758569
            ],
            [
                43.78526674007639,
                11.183372851822439
            ],
            [
                43.79443488391605,
                11.183372851822439
            ],
            [
                43.79443488391605,
                11.264311796355125
            ],
            [
                43.812771171595415,
                11.264311796355125
            ],
            [
                43.83110745927479,
                11.264311796355125
            ],
            [
                43.83110745927479,
                11.273305012414314
            ],
            [
                43.849443746954144,
                11.273305012414314
            ],
            [
                43.858611890793824,
                11.273305012414314
            ],
            [
                43.858611890793824,
                11.264311796355125
            ],
            [
                43.8769481784732,
                11.264311796355125
            ],
            [
                43.8769481784732,
                11.246325364236752
            ],
            [
                43.88611632231286,
                11.246325364236752
            ],
            [
                43.88611632231286,
                11.237332148177565
            ],
            [
                43.895284466152546,
                11.237332148177565
            ],
            [
                43.895284466152546,
                11.228338932118376
            ],
            [
                43.904452609992234,
                11.228338932118376
            ],
            [
                43.904452609992234,
                11.165386419704065
            ],
            [
                43.895284466152546,
                11.165386419704065
            ],
            [
                43.895284466152546,
                11.156393203644878
            ],
            [
                43.88611632231286,
                11.156393203644878
            ],
            [
                43.8769481784732,
                11.156393203644878
            ],
            [
                43.858611890793824,
                11.156393203644878
            ],
            [
                43.849443746954144,
                11.156393203644878
            ],
            [
                43.849443746954144,
                11.165386419704065
            ],
            [
                43.83110745927479,
                11.165386419704065
            ],
            [
                43.83110745927479,
                11.156393203644878
            ],
            [
                43.812771171595415,
                11.156393203644878
            ],
            [
                43.812771171595415,
                11.14739998758569
            ],
            [
                43.79443488391605,
                11.14739998758569
            ],
            [
                43.78526674007639,
                11.14739998758569
            ]
            ]
        ]
        },
        "docId": 1,
        "docVote": 0,
        "title": "title-1",
        "_id": {
        "$oid": "5248725d2dd5622510000001"
        }
    }

我使用此命令定义索引：

    db.search2.ensureIndex({"docVote": 1,"loc":"2dsphere"});

在集合上只有这个索引和“_id”字段的默认索引。

当我执行以下查询时，我希望“nscannedObjects”为= 10：

    db.search2.find({
        loc: {
        $geoIntersects: {
            $geometry: {
            type: "Polygon",
            coordinates: [
                [
                    [43.7269795, 11.1540365],
                    [43.8329368, 11.1540365],
                    [43.8329368, 11.3310908],
                    [43.7269795, 11.3310908],
                    [43.7269795, 11.1540365]
                ]
            ]
            }
        }
        }
    }, {
        "docVote": 1,
        _id: 0
    }).sort({
        "docVote": 1
    }).limit(10).hint({
        "docVote": 1,
        "loc": "2dsphere"
    }).explain()

但这是结果：

    {
    "cursor" : "S2Cursor",
    "isMultiKey" : true,
    "n" : 10,
    "nscannedObjects" : 44283,
    "nscanned" : 648117,
    "nscannedObjectsAllPlans" : 44283,
    "nscannedAllPlans" : 648117,
    "scanAndOrder" : true,
    "indexOnly" : false,
    "nYields" : 13,
    "nChunkSkips" : 0,
    "millis" : 12632,
    "indexBounds" : {

    },
    "nscanned" : 648117,
    "matchTested" : NumberLong(46642),
    "geoTested" : NumberLong(46642),
    "cellsInCover" : NumberLong(8),
    "server" : "*********"
    }

如果我从查询中删除sort，我会得到：

    {
        "cursor" : "S2Cursor",
        "isMultiKey" : true,
        "n" : 10,
        "nscannedObjects" : 10,
        "nscanned" : 25,
        "nscannedObjectsAllPlans" : 10,
        "nscannedAllPlans" : 25,
        "scanAndOrder" : false,
        "indexOnly" : false,
        "nYields" : 0,
        "nChunkSkips" : 0,
        "millis" : 3,
        "indexBounds" : {

        },
        "nscanned" : 25,
        "matchTested" : NumberLong(10),
        "geoTested" : NumberLong(10),
        "cellsInCover" : NumberLong(8),
        "server" : "******"
    }

那么，为什么索引不用于排序结果呢？从这个文件： http://docs.mongodb.org/manual/applications/geospatial-indexes/ http://docs.mongodb.org/manual/tutorial/sort-results-with-indexes/ 据我所知，MongoDb支持“带有标量索引字段（即升序或降序）的复合索引作为2dsphere索引字段的前缀或后缀”和“如果排序文档是复合索引的子集并从头开始在索引中，MongoDB可以使用索引来检索和排序查询结果。“

我错过了什么？

提前致谢

Answer 1

我的想法是因为你将docVote定义为复合索引中的第一个字段，但你不在查询中使用docVote。

我的建议是尝试db.search2.ensureIndex（{“loc”：“2dsphere”}）;查看查询是否使用索引。然后尝试db.search2.ensureIndex（{“loc”：“2dsphere”，“docVote”：1}）;

Answer 2

删除“loc”上的索引，并仅使用“docVote”索引。

Mongodb化合物2sphere指数不能按预期工作

2 个答案: