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- geoSearch
geoSearch¶
- geoSearch¶
The geoSearch command provides an interface to MongoDB’s haystack index functionality. These indexes are useful for returning results based on location coordinates after collecting results based on some other query (i.e. a “haystack.”)
The geoSearch command accepts a document that contains the following fields.
Field Type Description geoSearch string The collection to query. search document Query to filter documents. near array Coordinates of a point. maxDistance number Optional. Maximum distance from the specified point. limit number Optional. Maximum number of documents to return. readConcern document Optional. Specifies the read concern. The option has the following syntax:
readConcern: { level: <value> }
Possible read concern values are:
- "local". This is the default read concern level.
- "majority". Available for replica sets that use WiredTiger storage engine.
- "linearizable". Available for read operations on the primary only.
For more formation on the read concern levels, see Read Concern Levels.
For more information on the read concern levels, see Read Concern Levels.
Behavior¶
Unless specified otherwise, the geoSearch command limits results to 50 documents.
重要
geoSearch is not supported for sharded clusters.
Examples¶
Consider the following example:
db.runCommand({
geoSearch : "places",
near: [ -73.9667, 40.78 ],
maxDistance : 6,
search : { type : "restaurant" },
limit : 30
})
The above command returns all documents with a type of restaurant having a maximum distance of 6 units from the coordinates [ -73.9667, 40.78 ] in the collection places up to a maximum of 30 results.
Override Default Read Concern¶
To override the default read concern level of "local", use the readConcern option.
The following operation on a replica set specifies a Read Concern of "majority" to read the most recent copy of the data confirmed as having been written to a majority of the nodes.
注解
- To use read concern level of "majority",
- you must start the mongod instances with the --enableMajorityReadConcern command line option (or the replication.enableMajorityReadConcern set to true if using a configuration file).
- replica sets must use WiredTiger storage engine and election protocol version 1.
- Regardless of the read concern level, the most recent data on a node may not reflect the most recent version of the data in the system.
db.runCommand(
{
geoSearch: "places",
near: [ -73.9667, 40.78 ],
search : { type : "restaurant" },
readConcern: { level: "majority" }
}
)
To ensure that a single thread can read its own writes, use "majority" read concern and "majority" write concern against the primary of the replica set.