I have installed Flyway Software and trying to deploy code. I have a Scenario
I created a file V1_01_CREATE_TABLE.SQL to create a table.
Created a file V1_01_CREATE_PACKAGE.SQL - This package will hold code to insert a row into one of the columns in table created in step 1.
Created a file V1_01_02_ALTER_TABLE.SQL - This SQL will rename the column which was being referred in step2.
This will invalidate the package if I run 1, 2 & 3. How does FLYWAY handle such a situation? Does it understand object dependency?
As explained in the manual, Flyway simply passes your SQL scripts to the database to be executed, and records the success or failure of their execution.
Flyway has no interest or understanding of the content of your scripts. Flyway never looks at the content of those scripts. In that sense, there is no “intelligence” in Flyway.
Flyway is like the postal worker delivering your letters without opening the envelope. You are the author, and you take full responsibility for the logic and correctness of the SQL scripts. You are responsible for following the naming conventions so your scripts run in the correct order.
After initially creating its metadata table, Flyway makes very limited use of JDBC and SQL. Flyway does little more than make a connection to the database server, determine which of the scripts have yet to be run, and say to the database “Here, run this script, and this script, and then run this script.” while recording the success or failure of each run.
You should name your scripts in order they needs to be executed
V1.0.0_CREATE_TABLE.SQL
V1.0.1_CREATE_PACKAGE.SQL
V1.0.2_ALTER_TABLE.SQL
This will execute scripts in migrated
Related
I use flyway 8.5.0 and I want that my beforeMigrate or my afterMigrate sql is reported in the history table. Is this feaseable? or is there any config to setup this?
Then an other question: my repetable only runs when they change (checksum) but for my understanding the repetible sql should run every time. not so?
The beforeMigrate and afterMigrate SQL wont appear in your history table. If you look at the tutorial example for callbacks you can see that beforeMigrate can be called before the schema history table is created which would cause issues if it was trying to add itself to it. Additionally, I'm assuming these will be mostly static executions and would not really be part of the version history.
https://flywaydb.org/documentation/tutorials/callbacks
For repeatable, no they are only applied when the checksum has changed.
Repeatable migrations are very useful for managing database objects whose definition can then simply be maintained in a single file in version control. Instead of being run just once, they are (re-)applied every time their checksum changes.
https://flywaydb.org/documentation/tutorials/repeatable
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.
So while building a new database using our database migration scripts written in a springboot flyway project, we realized we made some mistakes.
Some old scripts need to be changed to ensure that we do not face these issues when we make a new database schema again. These issues are mostly related - an info table was not populated with entries in the project and there are scripts that refer to the data in the migration project -- this data does not exist because we never included a script to include data.
How can we correct this project - the only way I can think of is to correct scripts such that all inserts are replaced by - insert if not exists or replace create statements by create if not exists.
and then delete all entries in schema version and re-run this on all the database which are using this schema.
I cannot go back and correct my script because then the migration project will fail because of checksum issues.
You are rigth, if this project and the scripts are running in some existing projects you can not modify them because the checksum would fail.
Then the cleanest way I can think would be add a file called "DB-GENERAL-FIXES" or something like that, where you can add all SQL validations to restore the DB to a stable status. For the new implementations will be extra work first build it wrongly and then clean it, but if you are sharing the same code in production right now...is the best option
scenario: I have two databases.
The first database is a blank database used for testing. I essentially run flyway:migrate and build the database with complete schema and run my integration tests against that blank database. Any data that the integration tests need are inserted before the tests are run. Finally, the database is tore down by using flyway:clean to make sure the next build that comes through has a clean db to work with.
The second database has data in it.
Problem: The build fails in the integration phase because I have migration scripts that depends on data which database 1 doesn't have. Basically I'm inserting data based on certain data existing in the db.
Is the best common practice for flyway to only have ddl change type migration scripts and no data insert/update scripts?
Consider adding your reference data behind an IF statement in an afterMigrate callback:
http://flywaydb.org/documentation/callbacks.html
In the best case you add it as a migration and change it in the future via migrations. Including production. Things can be more complicated if that data can be changed on real environments by other means. In such case I would personally prefer to have a (shared) test fixture to insert the sample data.
I looked at the Flyway samples and documentation and tried to understand if it is useful in my environment.
The following conceptual detail is unclear to me: How does Flyway manage the changes between database versions? It obviously does NOT compare database life-instances (see answer here:Can Flyway find out and generate migration files from datamodel?)
In detail my setup looks like this:
I create SQL create and insert scripts when coding (automatically and manually). This means every version of my database is represented by a number of insert/create statements.
In my world I execute these scripts through a database tool (sqlplus from Oracle). Each run would setup the database _from_scratch_ (!).
Can I put these very same scripts 1 to 1 inside the "migration" path of Flyway? What happens if the target database is way older than the last "migration step" I did (or flyway did not yet exist when it was installed)?
Update:
I got some input from another Flyway user:
It seems like each "migration" (version of the database) has to be hand-written SQL/Java code and contains only "updates" from the previous "migration" of database.
If this is true, I wonder how this can be used with traditional coding technics: in my world SQL statements are generated automatically and contain all database init/create statements, not just "updates" to some previous version. If my SQL code generator could do that, then I wouldn't even need a tool like Flyway :-).
Your question about "how to handle a DB that has a longer history than there are migration scripts?" You need to create a V1_ migration/sql script that matches/recreates your latest DB schema. Something that can take a blank DB to what you have today. Create/generate that sql script using your existing DB tools and then put it in flyways migration directory. (And test V1 by using flyway against a clean DB and see if you get what you expect.) http://flywaydb.org/documentation/existing.html
After that point in time, all later versions must be added in as you work. When you decide you need a new table, in your dev environment, write a new V*_.sql that modifies your schema to the way you need it.
This blog goes over this situation for a Spring/SQL application. https://blog.synyx.de/2012/10/database-migration-using-flyway-and-spring-and-existing-data/