google-nomulus/db/README.md
gbrodman d88e6f54b9 Edit a couple of nits in the db README (#291)
* Edit a couple of nits in the db README

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## Summary
This project contains Nomulus's Cloud SQL schema and schema-deployment
utilities.
### Schema DDL Scripts
Currently we use Flyway for schema deployment. Versioned incremental update
scripts are organized in the src/main/resources/sql/flyway folder. A Flyway
'migration' task examines the target database instance, and makes sure that only
changes not yet deployed are pushed.
Below are the steps to submit a schema change:
* Define the incremental DDL script that would update the existing schema to
the new one.
* Add the script to the src/main/resource/flyway folder. Its name should
follow the V{id}__{description text}.sql, where {id} is a number that is
higher than all existing scripts in that folder. Also note that it is a
**double** underscore in the naming pattern.
* Run the `:db:test` task from the Gradle root project. The SchemaTest will
fail because the new schema does not match the golden file.
* Copy db/build/resources/test/testcontainer/mount/dump.txt to the golden file
(db/src/main/resources/sql/schema/nomulus.golden.sql). Diff it against the
old version and verify that all changes are expected.
* Rerun the `:db:test` task. This time all tests should pass.
Relevant files (under db/src/main/resources/sql/schema/):
* nomulus.golden.sql is the schema dump (pg_dump for postgres) of the final
schema pushed by Flyway. This is mostly for informational, although it may
be used in tests.
* db-schema.sql.generated is the schema generated from ORM classes by the
GenerateSqlSchema command in Nomulus tool. This reflects the ORM-layer's
view of the schema.
The generated schema and the golden one may diverge during schema changes. For
example, when adding a new column to a table, we would deploy the change before
adding it to the relevant ORM class. Therefore, for a short time the golden file
will contain the new column while the generated one does not.
### Non-production Schema Push
To manage schema in a non-production environment, use the 'flywayMigration'
task. You will need Cloud SDK and login once.
```shell
# One time login
gcloud auth login
# Deploy the current schema to alpha
gradlew :db:flywayMigrate -PdbServer=alpha
# Delete the entire schema in alpha
gradlew :db:flywayClean -PdbServer=alpha
```
The flywayMigrate task is idempotent. Repeated runs will not introduce problems.
The Flyway tasks may also be used to deploy to local instances, e.g, your own
test instance. E.g.,
```shell
# Deploy to a local instance at standard port as the super user.
gradlew :db:flywayMigrate -PdbServer=192.168.9.2 -PdbPassword=domain-registry
# Full specification of all parameters
gradlew :db:flywayMigrate -PdbServer=192.168.9.2:5432 -PdbUser=postgres \
-PdbPassword=domain-registry
```
### Production Schema Deployment
Schema deployment to production and sandbox is under development.