I have db named "mydb". Now How can I create a new db with name "mydb_test" with only schema of "mydb"
Tried the following link PostgreSQL how to create a copy of a database or schema?
As mentioned over there I tried the following command,
createdb -T olddb newdb
This copies including the data into newdb
If I try the second option mentioned in the above link I get following error,
# pg_dump -Cs -U postgres my_test_db > dump_schema_file
# psql -U postgres naggappan_my_test_db < dump_schema_file
psql: FATAL: database "naggappan_my_test_db" does not exist
How can I take only schema
You may create a new dump without data of required schema and then restore from it into a new DB:
# pg_dump --dbname=source_db_name --username=postgres --encoding=UTF8 --schema=db_schema --schema-only --file=path_to_filename.dump
# psql --dbname=target_db_name --username=postgres --file=path_to_filename.dump
If you have an existing dump with schema and/or data in binary format, you can restore only the schema from it using pg_restore:
# pg_restore --dbname=target_db_name --username=postgres --schema-only path_to_filename.dump
Related
i tried to create multiple rails app . I just deleted the file doing rm -rf . Now when im trying to create a new rails app with the same and do db:create , it tells me that ex: "blog_development" already exist . How can i delete the database that i created that i just deleted the directory but didn't drop the database ? .
I tried this in other rails app directory ActiveRecord::Migration.drop_table(:table_name) but it says the blog_development does not exist
You can do it in your DB console. For example, if you're using mysql:
Login to Mysql: mysql -u <username> -p
Delete the DB: DROP DATABASE <db_name>
Or you can just skip creating the database in your new app and just go straight to rake db:migrate
Step1 Capture backup from Heroku
Step2 Download latest.dump from Heroku with Postgres 10.2 version
Step3 Exporting Heroku Dump in my Local Postgres 9.6.
Result: its import all data but not creating sequences in by Database which producing error on each creation query.
You can export a sequence using the following command
pg_dump -t your_sequence_name
If you're not sure how your sequences are named, try this command using psql
\d your_table_name
You might also want to take a look at pg_dumpall
pg_dumpall > your_db.out
I am aware of the heroku pg:push command which pushes an entire database up to Heroku.
Now that I am launching my product, I would like to be able to push up only a specific table that contains information collected locally without overwriting existing tables (such as users).
Is there a command that enables me to only push specific tables to heroku?
My suggestion is to use PostgreSQL dump/restore capabilities directly using the pg_dump and psql commands.
With pg_dump you can dump a specific table from your local database
$ pg_dump --data-only --table=products sourcedb > products.sql
Then grab the Heroku PostgreSQL connection string from the configs
$ heroku config | grep HEROKU_POSTGRESQL
# example
# postgres://user3123:passkja83kd8#ec2-117-21-174-214.compute-1.amazonaws.com:6212/db982398
and restore the table in the remote database, using the information retrieved from Heroku.
$ psql -h ec2-117-21-174-214.compute-1.amazonaws.com -p 6212 -U user3123 db982398 < products.sql
You will need to customize the -p, -h and -U parameters, as well as the database name. The password will be prompted by psql.
You can also use the pg_restore to filter a dump and restore the table, but I personally prefer psql.
Note that Heroku is recommending the use of PostgreSQL tools in several documentations, such as Importing and Exporting for large data, or whenever the provided CLI commands don't cover specific cases like the one in this question.
I wrote script which extracts DB url from heroku. Then it dumps single tables from production and restores them on development/localhost. Run it like this:
rake production_to_development:run\['users;news;third_table',my-sushi-app\]
Code:
namespace :production_to_development do
task :run, [:tables, :app] => [:environment] do |t, args|
tables = args["tables"].split(';')
database_url = nil
Bundler.with_clean_env { database_url = `heroku config:get DATABASE_URL --app=#{args["app"]}` }
require 'addressable/uri'
uri = Addressable::URI.parse(database_url)
remote_database = uri.path[1,uri.path.length-2] # there is \n at the end of the path!
tables.each do |table|
backup_file = "tmp/#{table}.backup"
#bin_dir = "/Applications/Postgres.app/Contents/Versions/latest/bin"
bin_dir = ""
dump_command = "PGPASSWORD=#{uri.password} #{bin_dir}/pg_dump --file \"#{backup_file}\" --host \"#{uri.host}\" --port \"#{uri.port}\" --username \"#{uri.user}\" --no-password --verbose --format=c --blobs --table \"public.#{table}\" \"#{remote_database}\""
`#{dump_command}`
`psql -U 'root' -d my_table -c 'drop table if exists #{table}'`
`pg_restore -d my_table --no-owner #{backup_file}`
end
end
end
If I understand correctly, you just need a single database table with its locally created data pushed to your Rails production app. Maybe this is a simplistic approach, but you could create a migration for your table and then populate using db/seeds.rb.
After you've populated the seeds.rb file and pushed your repo to heroku:
heroku run rake db:migrate
heroku run rake db:seed
Also, if your local table has a ton of data and you're using Rails 4, check out the seed dump gem: https://github.com/rroblak/seed_dump. This will take your existing db data and map it to the seed format.
Can I add the migration file, but tell rails not to run it locally? I need the file for others to setup the application locally.
If you have a file:
db/migrate/20121010100909_modify_table_x.rb
You can go into your database and run the following SQL.
MySQL:
INSERT INTO 'schema_migrations' VALUES ('20121010100909');
PostgreSQL:
INSERT INTO schema_migrations VALUES ('20121010100909');
And it will then ignore that migration.
Edit - How to "go into your database"
Using the parameters from config/database.yml in Rails, connect to the database you are using.
You will need to use the command-line tool of whatever database software you're using. E.g.
For PostgreSQL:
psql -d <database_name> -U <username>
For MySQL:
mysql -u <username> <databasename>#localhost -p
Type in your password if required.
Then type in and execute the SQL above.
You could insert the proper timestamp into the schema_migrations table locally.
When running rake db:schema:dump on an app that uses a postgres schema (i.e. schema_name.users), it looks like it's only dumping tables for the first schema in the db user's search path. Is there a way to include tables from more than one schema?
To state the problem differently:
createdb myapp
psql myapp -U postgres -c "create table stuff"
#=> creates table "stuff" in the public schema
psql myapp -U postgres -c "create schema specific_thing"
psql myapp -U postgres -c 'create table "specific_thing".users(id int)'
createuser -U postgres -S -D -R special_user
psql myapp -U postgres -c "grant all on schema specific_thing to special_user"
psql myapp -U postgres -c "ALTER USER special_user SET search_path TO specific_thing,public"
In database.yml:
...
development:
adapter: postgresql
database: stuff
username: special_user
password:
host: localhost
...
Running: rake db:schema:dump
Only dumps the users talbe from the specific_thing schema and ignores everything in the public schema.
So here's what I found. I don't have the code in front of me so I can't point to anything specifically, but there is some code in PostgresAdapter that identifies what the adapter considers as its available 'tables'. The adapter assumes it's always going to deal with the 'public' schema (public is actually hardcoded in the query that gets a list of tables), so my solution to the problem involved subclassing PostgresAdapter to have a different concept of what it's 'tables' are. This got me most of the way there. There were some other obstacles to overcome but everything was much more clear after fitting this piece into the puzzle. Definitely involved spending some time in the Rails source though.