cursor.comment()¶

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Definition
Behavior
Example
Output Examples

Definition¶

cursor.comment()¶

3.2 新版功能.

Adds a comment field to the query.

cursor.comment() has the following syntax:

cursor.comment( <string> )

comment() has the following parameter:

Parameter	Type	Description
`comment`	string	The comment to apply to the query.

Behavior¶

comment() associates a comment string with the find operation. This can make it easier to track a particular query in the following diagnostic outputs:

See configure log verbosity for the mongod log, the Database Profiler tutorial, or the db.currentOp() command.

Example¶

The following operation attaches a comment to a query on the restaurants collection:

db.restaurants.find(
   { "borough" : "Manhattan" }
).comment( "Find all Manhattan restaurants" )

Output Examples¶

`system.profile`¶

The following is an excerpt from the system.profile:

{
   "op" : "query",
   "ns" : "guidebook.restaurant",
   "query" : {
      "find" : "restaurant",
      "filter" : {
         "borough" : "Manhattan"
      },
      "comment" : "Find all Manhattan restaurants"
   },
   ...
}

`mongod` log¶

The following is an excerpt from the mongod log. It has been formatted for readability.

重要

The verbosity level for QUERY must be greater than 0. See Configure Log Verbosity Levels

2015-11-23T13:09:16.202-0500 I COMMAND  [conn1]
   command guidebook.restaurant command: find {
      find: "restaurant",
      filter: { "borough" : "Manhattan" },
      comment: "Find all Manhattan restaurants"
   }
   ...

`db.currentOp()`¶

Suppose the following operation is currently running on a mongod instance:

db.restaurant.find(
   { "borough" : "Manhattan" }
).comment("Find all Manhattan restaurants")

Running the db.currentOp() command returns the following:

{
   "inprog" : [
      {
         "desc" : "conn5",
         "threadId" : "0x10772e000",
         "connectionId" : 5,
         "client" : "127.0.0.1:62560",
         "active" : true,
         "opid" : 2249279,
         "secs_running" : 0,
         "microsecs_running" : NumberLong(258562),
         "op" : "query",
         "ns" : "guidebook.restaurant",
         "query" : {
            "find" : "restaurant",
            "filter" : { "borough" : "Manhattan" },
            "comment" : "Find all Manhattan restaurants"
         },
         ...
      },
      ...
   ],
   "ok" : 1
}

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