repl_test:PRIMARY> show dbs admin 0.000GB direct_vote_resource 16.487GB local 14.860GB personas 30.809GB recommendation 0.370GB statistics_visit 0.138GB superpub 75.234GB test 0.000GB repl_test:PRIMARY> use superpub switched to db superpub repl_test:PRIMARY> db.ask.count() 123989434 repl_test:PRIMARY> db.ask.find({}).limit(1) { "_id" : ObjectId("5b1103341ac2386e164dd796"), "md5" : "b1b791efdb4745e0", "ans wer" : "成本和37砖混的差不多的、、不过保温隔热效果好的", "likenum" : 0, "keyword " : "海容", "question" : "用海容模块建大棚成本高不高??" } repl_test:PRIMARY> db.ask.distinct("md5").limit(3) 2018-11-23T15:27:29.186+0800 E QUERY [main] Error: distinct failed: { "ok" : 0, "errmsg" : "distinct too big, 16mb cap", "code" : 17217, "codeName" : "Location17217" } : DBCollection.prototype.distinct@src/mongo/shell/collection.js:1745:1 @(shell):1:1 repl_test:PRIMARY>
repl_test:PRIMARY> db.ask.aggregate([{$match:{}}, {$project:{"md5":true}}, {$group:{_id:"$md5"}}, {$group:{_id:null, count:{$sum:1}}}]) assert: command failed: { "ok" : 0, "errmsg" : "Exceeded memory limit for $group, but didn't allow external sort. Pass allowDiskUse:true to opt in.", "code" : 16945, "codeName" : "Location16945" } : aggregate failed _getErrorWithCode@src/mongo/shell/utils.js:25:13 doassert@src/mongo/shell/assert.js:16:14 assert.commandWorked@src/mongo/shell/assert.js:370:5 DBCollection.prototype.aggregate@src/mongo/shell/collection.js:1319:5 @(shell):1:1 2018-11-23T15:42:40.779+0800 E QUERY [main] Error: command failed: { "ok" : 0, "errmsg" : "Exceeded memory limit for $group, but didn't allow external sort. Pass allowDiskUse:true to opt in.", "code" : 16945, "codeName" : "Location16945" } : aggregate failed : _getErrorWithCode@src/mongo/shell/utils.js:25:13 doassert@src/mongo/shell/assert.js:16:14 assert.commandWorked@src/mongo/shell/assert.js:370:5