Get mysql info
$ brew info mysql
Install Mysql
$ brew install mysql
Start mysql server first:
$ brew services start mysql ==> Successfully started `mysql` (label: homebrew.mxcl.mysql)
Goto mysql console by:
$ mysql -uroot
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Category: database
Mongodb how to Import / Export in Linux/Mac
For Importing a mongodb use the following command
$ mongodump --db database_name
This will dump the json/bson files into dump/db_name folder
Or specify a directory with -o option
$ mongodump --db database_name -o path_to_folder
By specifying username and password
$ mongodump --db database_name -o /path/to/folder/ --username=my_user --password="my_password"
For Exporting a mongodb use the following command
$ mongorestore --db database_name path_to_the_json_bson_files
path_to_the_json_bson_files => That we already imported and stored before.
-
How to import only one document from a database and export into another database:
Import one document
$ mongodump --db=db_name --collection=collection_name --out=path_to_folder_to_import $ mongorestore --db=new_db_name --collection=collection_name path_to_folder_to_import/db_name/collection_name.bson
PostgreSQL 9.3 : Installation on ubuntu 14.04
Hi guys, I just started installing postgres on my ubuntu VM. I referred some docs, and followed this one: https://www.digitalocean.com/community/tutorials/how-to-install-and-use-postgresql-on-ubuntu-14-04
Its pretty much explained in this page. But just explaining here the important things.
You can install postgres by ubuntu’s own apt packaging system. Update local apt repository.
$ sudo apt-get update $ sudo apt-get install postgresql postgresql-contrib
Postgres uses role based access for the unix users. After the installation a default role called ‘postgres’ will be created. You can login to postgres account and start using or creating new roles with Postgres.
Sign in as postgres user
$ sudo -i -u postgres
Access the postgres console by
$ psql
But i cannot enter into the console and I got the following error:
postgres@8930a29k5d05:/home/rails/my_project$ psql
psql: could not connect to server: No such file or directory
Is the server running locally and accepting
connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
What could be the reason for this error?
So just gone through Postgres doc (http://www.postgresql.org/docs/9.3/static/server-start.html). You can see the same error under the section 17.3.2. Client Connection Problems. But the solution is not mentioned.
Original Reason: PostgreSQL Server was not running after the installation.
I tried rebooting the system and via init script the server should run automatically. But the server is not running again. I understood that something prevents postgres from running the server. What is it?
Just check your postgres server is running or not
$ sudo -aux | grep post postgres@8930a29k5d05:/home/rails/my_project$ ps -aux | grep postgres root 136 0.0 0.2 47124 3056 ? S 06:10 0:00 sudo -u postgres -s postgres 137 0.0 0.3 18164 3220 ? S 06:10 0:00 /bin/bash postgres 140 0.0 0.2 15572 2192 ? R+ 06:10 0:00 ps -aux postgres 141 0.0 0.0 4892 336 ? R+ 06:10 0:00 grep post
The server is not running.
Run the server manually by
root@8930a29k5d05:/home/rails/my_project# /etc/init.d/postgresql start
* Starting PostgreSQL 9.3 database server
[ OK ]
root@8930a29k5d05:/home/rails/my_project# ps aux | grep postgres
postgres 158 0.1 2.0 244928 20752 ? S 06:28 0:00 /usr/lib/postgresql/9.3/bin/postgres -D /var/lib/postgresql/9.3/main -c config_file=/etc/postgresql/9.3/main/postgresql.conf
postgres 160 0.0 0.3 244928 3272 ? Ss 06:28 0:00 postgres: checkpointer process
postgres 161 0.0 0.4 244928 4176 ? Ss 06:28 0:00 postgres: writer process
postgres 162 0.0 0.3 244928 3272 ? Ss 06:28 0:00 postgres: wal writer process
postgres 163 0.0 0.5 245652 6000 ? Ss 06:28 0:00 postgres: autovacuum launcher process
postgres 164 0.0 0.3 100604 3336 ? Ss 06:28 0:00 postgres: stats collector process
root 178 0.0 0.0 8868 884 ? S+ 06:28 0:00 grep --color=auto post
root@8930a29k5d05:/home/rails/my_project#
Now the server starts running. If still not works, then try to reconfigure your locales as mentioned here
$ dpkg-reconfigure locales
It is strange that, after installing such a popular database software, it doesn’t provide any information regarding the failure of its own server. It should give the developers some clue so that they can save their precious time.
The reason of this failure, what I concluded is
1. After installation we have to run the server manually
OR
2. I tried resetting the locales (So if no locales set in the machine may prevented the postgres from starting automatically?)
How to create a migration file dynamically by meta programming in rails 4.0
If you want to add a migration file from lib file or somewhere from your ruby file and execute it, use the dynamic method which can create a class or method dynamically. The following code snippet is not complete. But gives a better idea to create migration file dynamically. Use a bit of metaprogramming.
def create_columns(tb_with_cols)
.........
.........
columns.each { |column| add_columns << "\tadd_column(':#{tb_name}', :#{column})\n" }
columns
end
def migration_file_content(tb_with_cols)
<<-RUBY
class AddMissingColumnsToTable < ActiveRecord::Migration
def change_table
#{create_columns(tb_with_cols)}
end
end
RUBY
end
def write_content_to_file(path, content)
File.open(path, 'w+') do |f|
f.write(content)
end
end
Just call the method ‘migration_file_content’ in your code. Pass the parameter tb_with_cols as a Hash whose key is the table_name and value is the columns that should be added to that table like:
tb_with_cols = {:users => {:name => :string, :age => :integer, :address => :text} }
After that just call the method ‘write_content_to_file’ with your new migration file path and the content from our ‘migration_file_content’ method. 🙂
How to reinstall mongodb in ubuntu linux
Before reinstalling mongodb, in your linux system check whats installed in the system
$ sudo dpkg -l | grep mongo
ii mongodb-org 2.6.3 amd64 MongoDB open source document-oriented database system (metapackage)
ii mongodb-org-mongos 2.6.3 amd64 MongoDB sharded cluster query router
ii mongodb-org-server 2.6.3 amd64 MongoDB database server
ii mongodb-org-shell 2.6.3 amd64 MongoDB shell client
ii mongodb-org-tools 2.6.3 amd64 MongoDB tools
Remove all
$ sudo apt-get remove mongodb*
Install mongodb again, check mongodb org
$ sudo apt-get install -y mongodb-org
For particular version
$ sudo apt-get install -y mongodb-org=2.6.5 mongodb-org-server=2.6.5 mongodb-org-shell=2.6.5 mongodb-org-mongos=2.6.5 mongodb-org-tools=2.6.5
check whats newly installed
$ sudo dpkg -l | grep mongo
ii mongodb-org 2.6.8 amd64 MongoDB open source document-oriented database system (metapackage)
ii mongodb-org-mongos 2.6.8 amd64 MongoDB sharded cluster query router
ii mongodb-org-server 2.6.8 amd64 MongoDB database server
ii mongodb-org-shell 2.6.8 amd64 MongoDB shell client
ii mongodb-org-tools 2.6.8 amd64 MongoDB tools
check mongodb server status
$ sudo service mongod status
Start mongodb server
$ sudo service mongod start
Start mongo shell
$ mongo
check mongodb log file here
$ tail -n 200 /var/log/mongodb/mongod.log
How to reset the mysql password in redhat
Go to the mysql console and follow these steps
> use mysql;
> update user set password=PASSWORD("mynewpassword") where User='root';
> flush privileges;
> quit
ThinkingSphinx::SphinxError (undefined method `next_result’ for Mysql2 (rails 3)
I got this error after my thinking sphinx updation to the newest version of ‘3.0.5’. The error shows in the exact line of the code Model.search in my Rails controller. I updated my mysql2 version to ‘0.3.13’, and the issue is solved.
So in you Gemfile update the mysql2 version:
gem 'mysql2', '0.3.13'
And do
$ bundle install
