SchemaBridge.EF

SchemaBridge.EF is a lightweight helper library designed to simplify and standardize data migration when splitting a monolithic database into multiple databases or microservices.

It focuses on controlled, resumable, and verifiable data transfer between databases with identical or similar schemas, potentially using different database engines.

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Motivation

When migrating from a monolith to a microservice architecture, it is often necessary to extract parts of an existing database into new services.

Writing one-off migration scripts for each case is time-consuming and error-prone. SchemaBridge.EF provides a structured pipeline and reusable abstractions to speed up and standardize this process.

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Core Idea

With SchemaBridge.EF, you only need to implement:

• Table transporters — responsible for transferring table data
• Optional cache transporters — to track updates and deletions during migration
• Table checkers — to verify data integrity after transfer

The library handles discovery, execution order, batching, retries, and logging.

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Transfer Pipeline

The default transfer pipeline is executed in the following order:

1. Table transfer
2. Updated cache transfer (optional)
3. Removed cache transfer (optional)
4. Post-transfer checks

Each stage is automatically discovered and executed using reflection.

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Cache Tables (Updated / Removed)

During long-running migrations, data in the source database may continue to change. To avoid losing updates or deletions, SchemaBridge.EF supports cache-based tracking.

There are two cache types:

• Updated cache — tracks modified records
• Removed cache — tracks deleted records

These cache tables are optional.

If you do not need to track concurrent changes during migration, you may safely skip cache transporters entirely.

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Prerequisites Before Transfer

Before starting the transfer process, you should:

1. Create cache tables in the source database (if using cache transporters)
2. Add triggers that track updated and removed records
3. Disable auto-increment / identity generation on primary keys in the target database

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After Transfer

Once the migration is complete:

• Re-enable auto-increment / identity generation on primary keys in the target database
• Remove or disable cache triggers if they are no longer needed

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Interfaces

All required abstractions are defined in the SchemaBridge.EF.Interfaces namespace.

You implement these interfaces to describe how your data should be transferred and validated.

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Example

The project contains a full integration test demonstrating the complete transfer pipeline, including table transport, cache handling, and validation.

See: TransferServiceTests

This test uses in-memory databases and can be used as a reference implementation.

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Summary

SchemaBridge.EF helps you:

• Migrate data safely from monoliths to microservices
• Track updates and deletions during migration
• Validate transferred data
• Avoid writing fragile one-off scripts

The library is intentionally minimal and focused on migration logic only.