mongodb 导入导出

(mongoexport导出工具

MongoDB提供了mongoexport工具,可以把一个collection导出成json格式或csv格式的文件。可以指定导出哪些数据项,也可以根据给定的条件导出数据。工具帮助信息如下:


[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]#

下面我们将以一个实际的例子说明,此工具的用法:

将foo库中的表t1导出成json格式:

[root@localhost bin]# ./mongoexport -d foo -c t1 -o /data/t1.json   
connected to: 127.0.0.1   
exported 1 records   
[root@localhost bin]#



导出成功后我们看一下/data/t1.json文件的样式,是否是我们所希望的:

[root@localhost data]# more t1.json   
{ "_id" : { "$oid" : "4f927e2385b7a6814a0540a0" }, "age" : 2 }   
[root@localhost data]#



通过以上说明导出成功,但有一个问题,要是异构数据库的迁移怎么办呢?例如我们要将MongoDB的数据导入到MySQL该怎么办呢?MongoDB提供了一种csv的导出格式,就可以解决异构数据库迁移的问题了. 下面将foo库的t2表的age和name列导出, 具体如下:

[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]#

查看/data/t2.csv的导出结果:

[root@localhost data]# more t2.csv   
age,name   
1,"wwl"   
[root@localhost data]#



mongoimport导入工具

MongoDB提供了mongoimport工具,可以把一个特定格式文件中的内容导入到某张collection中。工具帮助信息如下:

[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.



下面我们将以一人实际的例子说明,此工具的用法:
先看一下foo库中的t1表数据:
> db.t1.find();   
{ "_id" : ObjectId("4f937a56450beadc560feaa9"), "age" : 5 }   
>



t1其中有一条age=5的记录, 我们再看一下json文件中的数据是什么样子的:

[root@localhost data]# more t1.json   
{ "_id" : { "$oid" : "4f937a56450beadc560feaa7" }, "age" : 8 }   
[root@localhost data]#



可以看到t1.json文件中有一条age=8的数据,下面我们将用mongoimport工具将json文件中的记录导入到t1表中:

[root@localhost bin]# ./mongoimport -d foo -c t1 /data/t1.json   
connected to: 127.0.0.1   
imported 1 objects



工具返回信息说明向表中插入了一条记录. 我们进库里实际验证一下:

[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 }   
>





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