主页 / user-14494

dancio's questions

Martin Hope
dancio
Asked: 2012-10-16 22:34:59 +0800 CST
  • 3

我有查询（这很慢~2,5s）：

db.markers.find({ latlng: { '$within': { '$box': [ [ -16, -140 ], [ 75, 140 ] ] } } }).sort({_id: -1}).limit(1000)

当我对此查询运行解释时，我得到

{
   "cursor" : "GeoBrowse-box",
   "isMultiKey" : false,
   "n" : 1000,
   "nscannedObjects" : 242331,
   "nscanned" : 242331,
   "nscannedObjectsAllPlans" : 242331,
   "nscannedAllPlans" : 242331,
   "scanAndOrder" : true,
   "indexOnly" : false,
   "nYields" : 1383,
    "nChunkSkips" : 0,
    "millis" : 2351,
    "indexBounds" : {
        "latlng" : [ ]
    },
    "lookedAt" : NumberLong(262221),
    "matchesPerfd" : NumberLong(242331),
    "objectsLoaded" : NumberLong(242331),
    "pointsLoaded" : NumberLong(0),
    "pointsSavedForYield" : NumberLong(0),
    "pointsChangedOnYield" : NumberLong(0),
    "pointsRemovedOnYield" : NumberLong(0),
    "server" : "xx:27017"
}

当我删除sort({_id: -1})时，解释给了我（快速查询5 毫秒）：

{
    "cursor" : "GeoBrowse-box",
    "isMultiKey" : false,
    "n" : 1000,
    "nscannedObjects" : 1000,
    "nscanned" : 1000,
    "nscannedObjectsAllPlans" : 1000,
    "nscannedAllPlans" : 1000,
    "scanAndOrder" : false,
    "indexOnly" : false,
    "nYields" : 0,
    "nChunkSkips" : 0,
    "millis" : 5,
    "indexBounds" : {
        "latlng" : [ ]
    },
    "lookedAt" : NumberLong(1000),
    "matchesPerfd" : NumberLong(1000),
    "objectsLoaded" : NumberLong(1000),
    "pointsLoaded" : NumberLong(0),
    "pointsSavedForYield" : NumberLong(0),
    "pointsChangedOnYield" : NumberLong(0),
    "pointsRemovedOnYield" : NumberLong(0),
        "server" : "xx:27017"
}

我在 latlng 上有 2d 索引，在 _id 上有 desc 索引和复合索引。

db.markers.ensureIndex({latlng: '2d', _id:-1})
db.markers.ensureIndex({ latlng: '2d' })
db.markers.ensureIndex({ _id: -1 })

我想要实现的是从最新排序的特定区域获取标记。

任何想法或建议如何在不到2.5 秒的时间内做到这一点？

mongodb spatial