NoSQL document oriented data access for .net systems with postgresql and marten
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The document discusses limitations of relational databases for domain-driven design (DDD) and presents document-oriented databases as a solution, specifically utilizing PostgreSQL with Marten as a document DB for .NET. It highlights the advantages of document models in handling complex object graphs and ensuring a focus on behavior and logic, enhancing the development process. The presentation concludes that combining SQL and NoSQL in PostgreSQL offers the best of both worlds, allowing for rich domain models in a single database environment.
![How document-oriented DBs come into play
● Single document per [whole] aggregate
● Can store complex object graphs
● Can store arrays, collections, nested objects
● No need for ORM
● No limitations for creating rich domain models
● Dev team focus is in on behavior and logic
● Models are easy to unit test
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NoSQL document oriented data access for .net systems with postgresql and marten
- 1. Document-oriented data access for domain-driven .NET systems with PostgreSQL & Marten Bojan Veljanovski, CTO at HASELT October, 2017 @ Macedonian .NET User Group 1
- 2. What we are going to talk about? ● Limitations in relational-only DBs for storing true domain aggregates ● How document-oriented DBs come into play ● Marten as document DB for .NET with PostgreSQL ● SQL + NoSQL => best of both worlds 2
- 3. Setting context ● How I got interested in document-oriented DBs? Why it makes so much sense? ● Why PostgreSQL? Why not MongoDb, CouchDb, RavenDb? What about SQL Server, MySQL? ● Who else uses this approach? 3
- 5. DDD Aggregate Cluster of domain objects that can be treated as a single unit. ● Consists of ○ Aggregate Root (or Root Entity) ○ Entities ○ Value Objects ○ Services ○ Repositories 5
- 6. Basic characteristics of an Aggregate Root ● Global identity ● Ensures invariants within aggregate ● Guarantees consistency ● Can reference other ARs only by identity ● Cannot reference non ARs ● Transactional consistency ● Stored and loaded in DB as a whole. 6
- 8. Sample domain model in code Let’s see the sample codebase in Visual Studio. 8
- 9. Limitations when working with domain models in relational-only DBs... ● Cannot store an array of values ○ Needs new table with 1-m relation ● ...an array of objects ○ Needs new table with 1-m relation ● …a nested object ○ Needs new table with 1-1 relation ● …an AR in a single table ○ AR is spanned across many tables, and needs joinsThese limitations often lead to... 9
- 10. These limitations often lead to... ● Complex O/R mapping code ● Sacrificing encapsulation for easier O/R mapping ● Leak of domain logic to upper layers ● Anemic domain models - only data, no behavior ● Dev teams focusing on data-relations instead of system behavior ● Implicit “SELECT N+1” problems ● Unit tests full with mocks & stubs 10
- 11. Moving out of the relational-only mindset From thinking in terms of relations and data To thinking in terms of behavior and data 11
- 13. How document-oriented DBs come into play ● Single document per [whole] aggregate ● Can store complex object graphs ● Can store arrays, collections, nested objects ● No need for ORM ● No limitations for creating rich domain models ● Dev team focus is in on behavior and logic ● Models are easy to unit test 13
- 15. Introducing PostgreSQL ● Object-relational database ● ACID ● Transactional ● Highly Extendable ● Open Source ● Free 15
- 16. PostgreSQL NoSQL data types ● Key/Value store ○ hstore ● Document store ○ json and jsonb ● Spatial and Geographic objects ○ postgis 16
- 17. PostgreSQL as document store: Creating table with JSONB column 17
- 21. Indexing documents Various indexes are supported. 21
- 22. Marten as Document DB for .NET with PostgreSQL 22
- 23. Introducing Marten ● OSS .NET library that provides polyglot persistence ● Document store ● Event store ● Uses PostgreSQL’s powerful JSON support ● Initial pre-alpha release on 08.12.2015 ● Current version 2.3.2 ● Community chat: gitter.im/JasperFx/marten 23
- 26. How our data looks like? -> User 26
- 27. Loading document by Id 27
- 28. Querying documents with LINQ 28
- 31. Querying with plain SQL through Dapper (yes, querying NoSQL documents with plain-old SQL) 31
- 32. Adding Foreign Key to Order document 32
- 33. How our data looks like with FK? -> Order 33
- 34. Querying multiple documents by using SQL JOIN 34
- 35. Other notable features in Marten as Document Db ● Foreign Keys ● Indexes ● Duplicate columns ● Batched queries ● Compiled queries ● Bulk insert ● Multitenancy ● Optimistic Concurrency 35
- 36. Closing 36
- 37. Summary ● Relational-only DBs limit the ability to craft good domain models ● Document DBs are natural fit for DDD Aggregates ● SQL + NoSQL in Postgres = best of both worlds in a single DB provider ● Marten helps .NET devs leverage PostgreSQL as polyglot database ● Polyglot data access mindset - there is no single approach 37
- 38. Resources ● Marten ○ https://jasperfx.github.io/marten ○ https://gitter.im/JasperFx/marten ● PostgreSQL JSON Functions and Operators ○ https://www.postgresql.org ● This presentation’s code samples ○ https://github.com/bojanv91/MartenPostgreSamples ● Other useful articles ○ https://martinfowler.com/bliki/AggregateOrientedDatabase.html 38