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When using AWS Aurora, a nullable column can be added to existing large (100k rows+?) tables without causing downtime. However, the migration may still timeout in GoCD - so please coordinate the release with DevOps.
- Make a new field addition in model with null=True.
- Generate the model-change migrations locally.
- Create a pull request containing the model change and newly-generated migrations.
- Merge the migration pull request.
- The release process will run the migration and add the nullable column to table.
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On AWS Aurora, indexes can be build on large tables without causing downtime, but this requires devops coordination as the migration may timeout in GoCD.
- Add the new index on model fields.
- Generate the model-change migrations locally.
- Make pull request containing the model change and newly-generated migrations.
- Merge the migration pull request.
- Release will run the migration and add the index to table.
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Checklist for adding indexes
- How long will it take? How big is the table?
- What is the read/write ratio on the table? What is the impact to writes?
- Should we alter an existing index rather than add a new one (left most columns, etc)
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