Mongodb Import and Export Methods
(Export tool
MongoDB provides the export tool to export a collection to a file in json or csv format. You can specify which data items to export or export data based on the given conditions. The tool help information is as follows:
- [root@localhost bin]# ./mongoexport --help
- options:
- --help produce help message
- -v [ --verbose ] be more verbose (include multiple times for more
- verbosity e.g. -vvvvv)
- -h [ --host ] arg mongo host to connect to ( /s1,s2 for sets)
- --port arg server port. Can also use --host hostname:port
- --ipv6 enable IPv6 support (disabled by default)
- -u [ --username ] arg username
- -p [ --password ] arg password
- --dbpath arg directly access mongod database files in the given
- path, instead of connecting to a mongod server -
- needs to lock the data directory, so cannot be used
- if a mongod is currently accessing the same path
- --directoryperdb if dbpath specified, each db is in a separate
- directory
- -d [ --db ] arg database to use
- -c [ --collection ] arg collection to use (some commands)
- -f [ --fields ] arg comma separated list of field names e.g. -f name,age
- --fieldFile arg file with fields names - 1 per line
- -q [ --query ] arg query filter, as a JSON string
- --csv export to csv instead of json
- -o [ --out ] arg output file; if not specified, stdout is used
- --jsonArray output to a json array rather than one object per
- line
- [root@localhost bin]#
The following is a practical example to illustrate the usage of this tool:
Export table t1 in the foo database to json format:
- [root@localhost bin]# ./mongoexport -d foo -c t1 -o /data/t1.json
- connected to: 127.0.0.1
- exported 1 records
- [root@localhost bin]#
After the export is successful, check whether the style of the/data/t1.json file is what we want:
- root@localhost data]# more t1.json
- { "_id" : { "$oid" : "4f927e2385b7a6814a0540a0" }, "age" : 2 }
- [root@localhost data]#
The export is successful as described above, but there is a problem: What should we do if the migration of heterogeneous databases is successful? For example, what should we do if we want to import MongoDB data to MySQL? MongoDB provides a csv export format to solve the migration problem of heterogeneous databases. The following section exports the age and name columns of table t2 of the foo database, as follows:
- [root@localhost bin]# ./mongoexport -d foo -c t2 --csv -f age,name -o /data/t2.csv
- connected to: 127.0.0.1
- exported 1 records
- [root@localhost bin]#
View the export result of/data/t2.csv
- [root@localhost data]# more t2.csv
- age,name
- 1,"wwl"
- [root@localhost data]#
Export Import Tool
MongoDB provides the volume import tool to import the content of a file in a specific format to a collection. The tool help information is as follows:
- [root@localhost bin]# ./mongoimport --help
- options:
- --help produce help message
- -v [ --verbose ] be more verbose (include multiple times for more
- verbosity e.g. -vvvvv)
- -h [ --host ] arg mongo host to connect to ( /s1,s2 for sets)
- --port arg server port. Can also use --host hostname:port
- --ipv6 enable IPv6 support (disabled by default)
- -u [ --username ] arg username
- -p [ --password ] arg password
- --dbpath arg directly access mongod database files in the given
- path, instead of connecting to a mongod server -
- needs to lock the data directory, so cannot be used
- if a mongod is currently accessing the same path
- --directoryperdb if dbpath specified, each db is in a separate
- directory
- -d [ --db ] arg database to use
- -c [ --collection ] arg collection to use (some commands)
- -f [ --fields ] arg comma separated list of field names e.g. -f name,age
- --fieldFile arg file with fields names - 1 per line
- --ignoreBlanks if given, empty fields in csv and tsv will be ignored
- --type arg type of file to import. default: json (json,csv,tsv)
- --file arg file to import from; if not specified stdin is used
- --drop drop collection first
- --headerline CSV,TSV only - use first line as headers
- --upsert insert or update objects that already exist
- --upsertFields arg comma-separated fields for the query part of the
- upsert. You should make sure this is indexed
- --stopOnError stop importing at first error rather than continuing
- --jsonArray load a json array, not one item per line. Currently
- limited to 4MB.
The following example shows how to use this tool:
Let's take a look at table t1 in the foo database:
- > db.t1.find();
- { "_id" : ObjectId("4f937a56450beadc560feaa9"), "age" : 5 }
- >
T1 contains a record with age = 5. Let's take a look at what the data in the json file looks like:
- [root@localhost data]# more t1.json
- { "_id" : { "$oid" : "4f937a56450beadc560feaa7" }, "age" : 8 }
- [root@localhost data]#
We can see that the t1.json file contains a data entry with age = 8. Next we will use the history import tool to import the records in the json file to table t1:
- [root@localhost bin]# ./mongoimport -d foo -c t1 /data/t1.json
- connected to: 127.0.0.1
- imported 1 objects
The returned information of the tool inserts a record into the table. We will verify it in the database:
- [root@localhost bin]# ./mongo
- MongoDB shell version: 1.8.1
- connecting to: test
- > use foo
- switched to db foo
- > db.t1.find();
- { "_id" : ObjectId("4f937a56450beadc560feaa9"), "age" : 5 }
- { "_id" : ObjectId("4f937a56450beadc560feaa7"), "age" : 8 }
- >