Can I replicate a schema using flyway from one environment to another.
Is it possible by one by one table or whole schema to replicate from Dev to Prod?
You could certainly share a set of migrations to be applied across multiple databases.
For example, you could have a structure:
db/migration/
--V2_base_schema.sql
--V3_base_data.sql
--V4_change_table.sql
--R__function.sql
as a resource bundle and provide the applicable runtime parameters to each environment in order to have the same migrations carried out on each database. Each database maintaining it's own schema_version, of course.
If you are asking if Flyway is the tool to somehow dump and restore, there is no such functionality - look to your databases native tools for that (eg pg_dump / pg_restore for PostgreSQL).
Related
Is it possible to use a different migration framework for your relational database with hasura?
I am seeing hasura has the ability to manage migrations as noted in the documentation here.
We are using liquibase as the migration framework for all of our other projects and want to use hasura, but keep our existing migration framework (liquibase).
In the setup documentation already linked above, there's a prompt that asks if you want to initialize the project with metadata and migrations. Is it as simple as saying no here?:
? Initialize project with metadata & migrations from https://docs-demo.hasura.app ? Yes
Can this be done or do you have to use the hasura migrations if you want to use hasura?
Yes, you can manage your database migrations however you want to, and you have no obligation to use Hasura. Hasura's migrations are just a collection of .sql files that can be applied/revoked sequentially.
What is critically important is that you keep Hasura's metadata in sync with the database state.
For example, if you're tracking a database column in Hasura, and you use a SQL client to drop that column in your DB, Hasura's metadata (which describes the tables, columns, etc. that are exposed through the API) will be inconsistent with the database state. The proper way to manage a task like that is to either (1) use the Hasura console UI, (2) use the Hasura metadata HTTP API, or (3) manually edit and apply metadata with the Hasura CLI.
The task of keeping Hasura metadata in sync with DB state becomes non-trivial very quickly as you start to make use of features like "actions" and "events". You should run through some real-life migration scenarios with your current set up to get a sense of the challenges.
We have not used Flyway from the beginning of our project. We are at an advanced state of development. An expert review has suggested to use Flyway in our project.
The problem is that we have moved part of our services (microservices) into another testing environment as well.
What is the best way to properly implement Flyway? The requirements are:
In Development environment, no need to alter the schema which is already existing. But all new scripts should be done using Flyway.
In Testing environment, no need to alter the schema which is already existing. But what is not available in testing environment should be created automatically using Flyway when we do migrate project from Dev to test.
When we do migration to a totally new envrionment (UAT, Production etc) the entire schema should be created automatically using Flyway.
From the documentation, what I understood is:
Take a backup of the development schema (both DDL and DML) as SQL script files, give a file name like V1_0_1__initial.sql.
Clean the development database using "flyway clean".
Baseline the Development database "flyway baseline -baselineversion=1.0.0"
Now, execute "flyway migrate" which will apply the SQL script file V1_0_1__initial.sql.
Any new scripts should be written with higher version numbers (like V2_0_1__account_table.sql)
Is this the correct way or is there any better way to do this?
The problem is that I have a test database where we have different set of data (Data in Dev and test are different and I would like to keep the data as it is in both the environments). If so, is it good to separate the DDL and DML in different script files when we take it from the Dev environment and apply them separately in each environment? The DML can be added manually as required; but bit confused if I am doing the right thing.
Thanks in advance.
So, there are actually two questions here. Data management and Flyway management.
In terms of data management, yes, that should be a separate thing. Data grows and grows. Trying to manage data, beyond simple lookup tables, from source control quickly becomes very problematic. Not to mention that you want different data in different environments. This also makes automating deployments much more difficult (branching would be your friend if you insist on going this route, one branch for each data set, then deploy appropriately).
You can implement Flyway on an existing project, yes. The key is establishing the baseline. You don't have to do all the steps you outlined above. Let's say you have an existing database. You have to get the script that defines that database. That single script should include all appropriate DDL (and, if you want, DML). Name it following the Flyway standards. Something like V1.0__Baseline.sql.
With that in place, all you must do is run:
flyway baseline
That will establish your existing code base as the start point. From there, you just have to create scripts following the naming standard: V1.1xxx V2.0xxx V53000.1xxx. And run
flyway migrate
To deploy appropriate changes.
The only caveat to this is that, as the documentation states, you must ensure that all your databases match this V1.0 that you're creating and marking as the baseline. Any deviation will cause errors as you introduce new changes and migrate them into place. As long as you've got matching baseline points, you should be able to proceed with different data in different environments with no issues.
This is my how-to instruction on integration flyway with prod DB: https://delicious-snipe-938.notion.site/How-to-integrate-Flyway-with-existing-MySQL-DB-in-Prod-PostgreSQL-is-similar-1eabafa8a0e844e88205c2f32513bbbe.
I have delivered a Product to the customer. Now I have upgraded the Product, which includes changes to the database.
Customer wants to upgrade the Product. Now will Flyway help in the migration of Customer data from older version to newer version. Please let me know, if this is a valid use case. The flyway documentation talks about its use during development only.
Flyway allows you to change your database by running a set of scripts in a defined order. These scripts are called 'migrations' as they allow you to 'migrate' your database from one version to another.
The idea is you can start with an an empty database and each migration script will successively bring that database up from empty up to the current version. However, it's also possible to start with an existing database by creating a 'baseline' migration.
As SudhirR said, Flyway's primary use case is to define schema changes. However, it's perfectly possible to change data also. Since Flyway is just running plain SQL, in principle almost anything you can do in a SQL script you can also do in a Flyway migration.
In the case you described it should be possible to use Flyway to migrate the customer database. The steps you could take are:
Generate a sql script that includes the entire DDL (including indexes, triggers, procedures, ...) of the production database. To do this you will need to add insert statements for all the reference data present in the database.
Save this script in your Flyway project as something like 'V1__base_version.sql'
Run the flyway baseline command against your production database
This will set up your production database for use with Flyway
Add a new migration script to migrate your customer's data to the new version
e.g. create new table, copy data from old table to new table, delete old table
Run flyway migrate to upgrade production
These steps are adapted from the Flyway documentation page here.
Of course you should read the Flyway docs and manually test on a throwaway DB before you run anything against production. However I think in principle Flyway could be a good fit for your use case.
Flyway should be used for schema migrations and any reference data (basic data that is required by the system/application in order to function properly).
Putting client specific data migrations would not be a use case. However, if you can represent the data migration "generically" by not using IDs and instead use names or types than it could be a candidate. Meaning if you could write a migration in a way that could be applied to all clients, then that would be the use case to put it in as a flyway migration.
Otherwise data migrations would be applied in some other way outside of the process like requesting special access to the database or having some team that manages the database to apply the scripts.
If you are doing custom data modifications quite often then I'd say something is wrong in some other area of the SDLC and you may need to increase testing so that bugs don't mess up the data in the first place.
My current project has a few Flyway migrations in place that are used to import initial data into a database. This data is convenient especially for developers to be able to quickly setup the project. Production data is imported through some batch jobs and has a newer version.
Some of these migrations are quite big (~20MB) and so everytime the application starts, Flyway takes some time to calculate the checksum of the migrations. This also is a problem for integration tests as they also take longer because of this.
I consider this approach to be a misuse of Flyway, I think migration tools should be used mainly for structural data.
I want to remove those files from our application and rather use a configuration management tool (e.g. Vagrant, Puppet, Chef) to import test data on developer environments. However, I can't just delete the migration files from the application as Flyway will complain that a migration has been recorded in the database but is not present in the application migrations.
My first thinking was to create a new migration with a high-priority version number that will
Delete the test data
Delete the migration from the schema_version table
and then remove the migration scripts. This however does not work, Flyway still complains that the removed migration script is missing.
Is there a restriction that you cannot interact with the schema_version table in migrations?
What other options do I have? If at all possible I want to do this using Flyway and not manually.
Repair is your best bet. Empty those data migrations and run the repair command to have their checksums recalculated based on the empty files.
I think the documentation (http://flywaydb.org/getstarted/existingDatabaseSetup.html) is not clear enough and would like the description to be illustrated with an example. I have one for you:
Let's say we have two different versions (1 and 2) of the production database whose schema version is implicit but deterministic by querying the existing tables. How will we then achieve what is described in the documentation?
In my example the two versions both have a script attached:
Version 1: Create table A
Version 2: Create table B
I have created java migration files matching the scripts for versions 1 and 2 but since the flyway metadata is missing I need to query the database whether the scripts have been run and skip them in that case. The problem is that the application crashes since Flyway has not been initialised.
I don't want to initialise Flyway from the commandline since I want this to be done automatically upon deployment (Flyway in embedded mode). From what I've seen this only works with empty databases.
Is there a simple solution to this problem?
For single PROD databases, you can use flyway.initOnMigrate
In your case you would have to wrap Flyway and recreate this manually by inspecting your tables and calling either init with flyway.initialVersion=1 or with flyway.initialVersion=2, followed by a call to migrate.