What options do I have to migrate data to hosted with Heroku Postgres Database?
I have Django app and my client is migrating is moving from his existing software will most likely produce data in excel format. I will figure out the data model and data conversion I just need to know what tools to use to do the actual update of the DB.
Your Question is probably too broad for this site. But briefly, for Postgres in general…
INSERT
The usual way to put data into a SQL database is the INSERT command.
COPY FROM
To add data in bulk rather than one record at a time, call COPY FROM. You specify a file to be imported.
Related
currently I am using PostgreSQL database in my project but I also want to use SQLite for localhost, so I want to run migrate command but there are errors because in SQLite array field is not used so I want to convert array field to JSONfield and makemigrations but in migrations old migrations also present. S I want to write custom logic in migrations. So, it use old migrations when database is PostgreSQL and new migrations when it is sqlite3.
I don't want create new migrations and migration table every time I switch databases.
SQLite is more of a flat file system. I think the original idea is that you can store a small amount of data on a device and update the main database, or fetch info from a database, when the device is 'idle' as a background process. I know there may be some people putting this comment down but essentially SQLite is 'Light' and a flat file. Those considerations should be taken into account. btw I see that there is MYSQL for Andriod but I have not tried it out.
i'm looking for a "best-practice" guide/solution to the following situation.
I have a Django project with a MySql DB which i created and manage. I have to import data, every 5 minutes, from a second (external, not managed by me) db in order to do some actions. I have read rights for the external db and all the necessary information.
I have read the django docs regarding the usage of multiple database: register the db in settings.py, migrate using the --database flag, query/access data by routing to the db (short version) and multiple question on this matter on stackoverflow.
So my plan is:
Register the second database in settings.py, use inspectdb to add to the model, migrate, define a method which reads data from the external db and add it to the internal (own) db.
However I do have some questions:
Do i have to register the external db if i don't manage it?
(Most probably yes in order to use ORM or the cursors to access the data)
How can i migrate the model if I don't manage the DB and don't have write permissions? I also don't need all the tables (around 250, but only 5 needed).
(is fake migration an option worth considering? I would use inspectdb and migrate only the necessary tables.)
Because I only need to retrieve data from the external db and not to write back, would it suffice to have a method that constantly gets the latest data like the second solution suggested in this answer
Any thoughts/ideas/suggestions are welcomed!
I would not use Django's ORM for it, but rather just access the DB with psycopg2 and SQL, get the columns you care about into dicts, and work with those. Otherwise any minor change to that external DB's tables may break your Django app, because the models don't match anymore. That could create more headaches than an ORM is worth.
I migrated a database that was manipulated via SQL to use Django's migration module: https://docs.djangoproject.com/en/3.0/topics/migrations/.
Initially I thought of using migrations only for changes in the model such as changes in columns or new tables, performing deletes, inserts and updates through SQL, as they are constant and writing a migration for each case would be a little impractical.
Could using the migration module without using data migrations cause me some kind of problem or inconsistency in the future?
You can think about data migration if you made a change that required also a manual fix on the data.
Maybe you decided to normalize something in the database, e.g. to split a name column to the first name and the last name. If you have only one instance of the application with one database and you are the only developer then you will also not write a data migration, but if you want to change it on a live production site with 24 x 7 hours traffic or you cooperate with other developers then you probably prepare a data migration for their databases or you will thoroughly test the migration on a copy of live data that the update will work on the production site correctly without issues and with minimal shutdown. If you don't write a data migration and you had no problem immediately then it is OK and will be not worse then a possible ill-conceived data migration.
I am recreating a web app in Django that was running in a server but it was terminated, fortunately, I did a backup of all the code. My problem comes with the database because but I do not know how to transfer all the data from the old db.sqlite3 Django database web app into the new one.
I found a similar question as mine Django: transfer data from one database to another but the user wanted to transfer data from specific columns because their models.pyfrom the old and new databases were slightly different. In my case, my models.py from the old and new databases are the same.
Alternatives
I am using the DB Browser for SQLite to explore the content of the old database and I could add manually each row into the Django administration but this will take me too much time.
I could copy the old db.sqlite and replace it in the new web app because the models.py file remains the same but this solution is not appropriate IMO, this solution is rude and I think it goes against the good practices of Software.
How should I proceed for transferring data from the old database to the new one?
This seems like a one time copy of one db to another. I don't see how this goes against good software practice unless you have to be copying this db frequently. I've done it before when migrating servers and it doesn't cause any issues assuming the two instances of the application are the same build.
I was able to do some minor tricks in order to solve my problem because there is not a straightforward functionality that allows you to transfer all your data from two sqlite databases in Django. Here is the trick I did:
Download the sqlite db browser to explore and export the contents of your old database in a .csv file. Open you database with sqlite db browser and hit on the tables option and you will see all your tables, then do a right click on any of those and hit the export as a csv file option to generate the csv file (name_of_your_csv_file.csv). The other alternative is to use the sqlite3.exe to open your database in cmd or powershell and then doing the export with:
.tables #this lets you explore your available tables
headers on
mode csv
output name_of_your_csv_file.csv
2.There are two choices up to this point: You can either insert all the records at once to your new database or you can drop your existing tables from the new database and then recreate them and import the .csv file. I went for the drop option because there were more than 100 records to migrate.
# sqlite3
# check the structure of your table so you can re-create it
.schema <table_name>
#the result might be something like CREATE TABLE IF NOT EXISTS "web_app_navigator_table" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "ticket" varchar(120) NOT NULL);
#drop the table
drop table web_app_navigator_table
#re-create the table
create table web_app_navigator_table(id integer not null primary key autoincrement, ticket varchar(120) not null);
#do the import of the csv file
.import C:/Users/a/PycharmProjects/apps/navigator/name_of_your_csv_file.csv table_name_goes_here
You might see an error such as csv:1: INSERT failed datatype mismatch but this indicates that the first row of your csv file was not inserted because it contains the headers of the exported data from your old database.
I'm pretty new to Django and it's deployment on Heroku.
I've got a Postgres database up and running on the app server. My app requirements need me to add a new column to my existing database which has a sizable amount of data in it, which I can't lose.
Looking around, I found a solution described by Mike Ball here.
I have the following queries though:
What exactly is South? (I read the docs but didn't get a clear idea)
Will it help me save and move my existing data from my current database?
As a complete newbie, is the above link an easy way to move the data?
Also, in general, if you could hook me up with a good guide for general DBMS concepts, I'd be very grateful.
Thanks!
What exactly is South? (I read the docs but didn't get a clear idea)
south migrates your database schema as it changes in time. the schema has to start with a django models.py file. If you use 'manage.py syncdb ...' to create your database then you can probably use south.
Will it help me save and move my existing data from my current database?
As long as you used syncdb to create your database using a models.py file in django, then south can change that database and add the new column. basically, south records the changes you make to the models.py file in migration files, then you can apply those migration files to your database which update it non-destructively.
As a complete newbie, is the above link an easy way to move the data?
south doesn't move your data. it allows you to add the new columns to your existing database without destroying the database. to move your data you will need to backup the data to a file, then copy the file to another machine, then restore the backup. That's not what south does.