NickName:BoriS Ask DateTime:2015-09-30T21:24:09

Drop empty databases from MongoDB

I have a bunch of empty databases showing up in my MongoDB (from time to time, and for an unknown reason) and I'm looking for an easy way to drop all of the empty ones. Here is a piece of the results of the 'show dbs' command, and it's clear which ones are empty and which is not.

rs0:PRIMARY> show dbs
1442036273           (empty)
1442643016           (empty)
1443249599           (empty)
<script>document     (empty)
<script>foo<         (empty)
CFIDE                (empty)
CSCOnm               (empty)
CVS                  (empty)
ConsoleHelp          (empty)
ControllerWeb        (empty)
DB4Web               (empty)
MYDB                 0.203GB
HNAP1                (empty)
IDMProv              (empty)
MM                   (empty)
MSWSMTP              (empty)
NASApp               (empty)
Orion                (empty)
OvCgi                (empty)
Reporting            (empty)
SAPHostControl       (empty)
...

Any ideas?

Copyright Notice：Content Author:「BoriS」，Reproduced under the CC 4.0 BY-SA copyright license with a link to the original source and this disclaimer.
Link to original article：https://stackoverflow.com/questions/32867307/drop-empty-databases-from-mongodb

Answers

chridam 2015-09-30T13:49:29

Use the listDatabases command to get the array of databases which have empty data, iterate over the list and call the dropDatabase method on the database object. The following demonstrates this\n\n> use admin\n> var dbs = db.adminCommand(\"listDatabases\").databases\n> printjson(dbs)\n[\n {\n \"name\" : \"admin\",\n \"sizeOnDisk\" : 83886080,\n \"empty\" : false\n },\n {\n \"name\" : \"local\",\n \"sizeOnDisk\" : 83886080,\n \"empty\" : false\n },\n {\n \"name\" : \"test\",\n \"sizeOnDisk\" : 486539264,\n \"empty\" : false\n },\n {\n \"name\" : \"test2\",\n \"sizeOnDisk\" : 0,\n \"empty\" : true\n },\n {\n \"name\" : \"test3\",\n \"sizeOnDisk\" : 0,\n \"empty\" : true\n }\n]\n> var emptyDbs = dbs.filter(function(db){ return db.empty; });\n> printjson(emptyDbs)\n[\n {\n \"name\" : \"test2\",\n \"sizeOnDisk\" : 0,\n \"empty\" : true\n },\n {\n \"name\" : \"test3\",\n \"sizeOnDisk\" : 0,\n \"empty\" : true\n }\n]\n\n> emptyDbs.forEach(function(e){\n var db = new Mongo().getDB(e.name);\n db.dropDatabase();\n})\n",

Harsh Makani 2015-09-30T13:48:03

you can create a javascript loop that do the job and then execute it in the mongoconsole.\n\nvar dbs = db.getMongo().getDBNames()\nfor(var i in dbs){\n if (db.getCollectionNames() != null) {\n continue;\n }\n db = db.getMongo().getDB( dbs[i] );\n print( \"dropping db \" + db.getName() );\n db.dropDatabase();\n}\n\n\nsave it to dropemptydbs.js and then execute:\n\nmongo dropemptydbs.js\n",