Selfelected

A talk about pros and cons with O/RM

These are my pages from my talk about pros and cons with “fat” O/RM today.
As zip.

# O/RM

myname@omegapoint.se Göteborgs-kontoret

https://selfelected.com/
https://ideas.selfelected.com/
https://github.com/LosManos

# O/RM

myname@omegapoint.se Göteborgs-kontoret


Resultat: Ifrågasätt

# O/RM

myname@omegapoint.se Göteborgs-kontoret

Föredraget förutsätter en vag förståelse av ORM.
Fet orm (EF/Hibernate/cache). Micro-orm. (mappning av data och datatyper)
Att det är en översättning från RDb:ns mängdbaserade struktur till det imperativa språkets list-baserade; och tvärtom.

# O/RM

myname@omegapoint.se Göteborgs-kontoret

3 skäl
* Typsäkerhet
* Höger-vänster
* Refaktorering

# O/RM

myname@omegapoint.se Göteborgs-kontoret

Ökad komplexitet

Utsuddade gränser

Choke point

# O/RM

myname@omegapoint.se Göteborgs-kontoret

3 skäl
Typsäkerhet
ändras inte så ofta det så när det väl är mappat
Höger-vänster
ändras ofta i början men tenderar att stabiliseras
Refaktorering
man kan bara automatrefaktorera namn och typer. strukturer är manuellt arbete

# O/RM

myname@omegapoint.se Göteborgs-kontoret

https://www.selfelected.com/the-tree-reasons-to-use-an-o-rm/
https://dapper-tutorial.net/dapper

The three reasons to use an O/RM

1. Type security
2. Data copying Entity/Recordset
3. Faster turn around with a moving schema

If these 3 issues aren’t a problem in you case, be reluctant to use an O/RM as an O/RM brings a bunch of other problems.

Type security

When you get the Customer.Verified out of a database the code already knows it is a boolean. No explicit type casting or declaring is needed as it is done elswhere, once and for all.

Now this isn’t totally true but depends on whether LINQ or HQL (or for another O/RM) you are using. But basically it is true, because of solid Right-left copying

Right-left data copying

Copying data from a recordset to the Entity is done by the OR/M and configured once and for all. Unlike a programmer it won’t forget to copy a field in an obscure corner in your code base.

It isn’t hard to write a data copying function for this simple case and dragging a whole OR/M into the project is a lot of dependencies for little use.

Turn around

When the scheme is changing fast, like in the beginning of a project, or when prototyping, an O/RM is of great help to change in one place and let the coding tools and compiler do the rest of the changes in the project.

Schemes tend to solidify after a while and only change in small increments so speeding up the first 3 months for having a rucksack the coming 6 years might not be the best solution.