原始explain函数 [1]¶

备注

Although MongoDB provides the explain command, the preferred method for running explain is to use the db.collection.explain() and cursor.explain() helpers.

语法:

{
   explain: <command>,
   verbosity: <string>,
   comment: <any>
}

verbosity:

"queryPlanner"
"executionStats"
"allPlansExecution" (Default)

comment

实例:

db.runCommand(
   {
     explain: { count: "products", query: { quantity: { $gt: 50 } } },
     verbosity: "queryPlanner"
   }
)

实战¶

我想explain带limit的count，但如下命令不可用:

db.zwg_log.explain("executionStats").count({
  "user_id": "ceafb78f483180b651f76b185ce0e3ab",
  "is_delete": "0"
}).limit(30)

需要使用:

db.runCommand({
  explain: {
    count: "zwg_log",
    query: {
      "user_id": "ceafb78f483180b651f76b185ce0e3ab",
      "is_delete": "0"
    },
    limit:30
  },
  verbosity: "executionStats"
})