Linux Ask! is a Q & A web site specific for Linux related questions. Questions are collected, answered and audited by experienced Linux users.
Repair and compact database in MongoDB
Answer:
To repair and compact a database in MongoDB, you can use the following command in the mongodb Interactive shell.
1. Select the database
use test
2. Repair the current database
db.repairDatabase()
Done.
Count the total number of objects in the collection in MongoDB
Answer:
In MongoDB, to count the total number of objects in the collection, you can use the following statement in the mongodb Interactive shell.
db.test.count()
The above statement will return the total number of objects in the collection "test"
Creates an index in MongoDB
Answer:
In an given collection, if you want to add an index on a specify field, you can do the following in the mongodb Interactive shell.
db.test.ensureIndex( { name : 1 } )
The key "name" from now on will have index enabled.
How to add a directory into the PATH environment variable?
Answer:
To add a new directory into the PATH environment variable, you can use the following command.
# export PATH=$PATH:/opt/myprogram/bin
If you want to have this path being set automatically, then follow this article.
Show the storage used by a database in MySQL
Answer:
In previous article, we have already discussed how to list the database size in your MySQL server.
But if you want to have a more detail view on an individual database, you can try the following (crazy) SQL.
SELECT s.schema_name,
CONCAT(IFNULL(ROUND((SUM(t.data_length)+SUM(t.index_length))
/1024/1024,2),0.00),"Mb") total_size,
CONCAT(IFNULL(ROUND(((SUM(t.data_length)+SUM(t.index_length))-SUM(t.data_free))/1024/1024,2),0.00),"Mb")
data_used,
CONCAT(IFNULL(ROUND(SUM(data_free)/1024/1024,2),0.00),"Mb") data_free,
IFNULL(ROUND((((SUM(t.data_length)+SUM(t.index_length))-SUM(t.data_free))
/((SUM(t.data_length)+SUM(t.index_length)))*100),2),0) pct_used,
COUNT(table_name) total_tables
FROM INFORMATION_SCHEMA.SCHEMATA s
LEFT JOIN INFORMATION_SCHEMA.TABLES t ON s.schema_name = t.table_schema
WHERE s.schema_name = "mydatabase"
GROUP BY s.schema_name
ORDER BY pct_used DESC\GIt will give you something like the following..
schema_name: mydatabase
total_size: 165.09Mb
data_used: 12.09Mb
data_free: 153.00Mb
pct_used: 7.33
total_tables: 133