5 ms·

It seems to me that in discussions of NoSQL vs relational databases, one of the main arguments that comes up regarding ease of design and maintenance is "you ca

It seems to me that in discussions of NoSQL vs relational databases, one of the main arguments that comes up regarding ease of design and maintenance is "you can just use an ORM". But I see major disadvantage after major disadvantage of using an ORM, and there seems to be some overlap with the disadvantages of NoSQL (by which I am primarily referring to document-oriented databases). I really can't tell, once you factor these disadvantages in, what comes out on top.

nbouscal 13y ago
I don't think one is inherently superior to the other, it just depends on the data. If you have highly structured data for which integrity is mission-critical, you want to be using a RDBMS. If you have unstructured data for which throughput is mission-critical, you'll probably benefit from using a NoSQL system.
andrewflnr 13y ago
I'm sure someone has tried, but has anyone done a good job on an ORM that actually lets you select which columns to load and only selects those?
- fatalmind 13y ago
  here you go: http://use-the-index-luke.com/sql/join/hash-join-partial-objects#orm-partial-objects http://use-the-index-luke.com/sql/join/hash-join-partial-obj... It's really a PIA. Recently, I've learned about http://jooq.org/ http://jooq.org/ — not having checked in detail yet, it might be easier there.
- riffraff 13y ago
  Don't most ORM allow that? i.e. rails' ActiveRecord allows you to select columns easily in most cases: User.where(..) # all fields User.where(..).select(:name, :id) # only two of them joe.boards.select(:title) # only one in join joe.boards.pluck(:title) # only column value instead of full objects with one attribute set Though I recall it's involved for #belongs_to relations. You should also be able to setup the select as a default per-class, other than per query. I suspect, I likely didn't understand your question, could you expand it?
  - andrewflnr 13y ago
    It's possible I'm just ignorant of the capabilities of most ORMs. My only real experience is with the Django ORM. AFAIK, if you select an object, it wants to make sure all the members of the object are populated. My apologies if it was a dumb question. :)
    - byroot 13y ago
      By default yes, but like most ORMs you can ask to populate only some members: https://docs.djangoproject.com/en/dev/ref/models/querysets/#only https://docs.djangoproject.com/en/dev/ref/models/querysets/#...
    - meric 13y ago
      Django has it too. https://docs.djangoproject.com/en/dev/ref/models/querysets/#defer https://docs.djangoproject.com/en/dev/ref/models/querysets/#...
- barrydahlberg 13y ago
  .NETs Entity Framework lets you do this using the fantastic LINQ syntax. Commonly you will say which objects to select, then give a projection into a new anonymous type with only the columns you want.
  - wtetzner 13y ago
    It would be much nicer to use if C# had structural typing for the anonymous types, so you could usefully return them.
- acdha 13y ago
  Django offer a couple of options: .only(… field list…) .defer(… fields to fetch on demand…) https://docs.djangoproject.com/en/dev/ref/models/querysets/#only https://docs.djangoproject.com/en/dev/ref/models/querysets/#...
- aidos 13y ago
  SQL alchemy - it does everything the right way. http://www.sqlalchemy.org/ http://www.sqlalchemy.org/
bcoates 13y ago
The ORM I really want just takes my SQL and a connection to my database at compile or load time, and wires it up to the type system of the language I'm using. All the ones I've tried just seem to embrace the awfulness of the low-level database access APIs and are just trying to replace the good-enough DSL that is SQL with something worse.
- tmcneal 13y ago
  The closest I've seen an ORM come to this is Squeryl: http://squeryl.org http://squeryl.org
  - oacgnol 13y ago
    Which has been superseded by Slick (http://slick.typesafe.com/ http://slick.typesafe.com/) and does exactly as the parent says.
- johnpmayer 13y ago
  http://www.haskell.org/haskellwiki/MetaHDBC http://www.haskell.org/haskellwiki/MetaHDBC Does exactly that. Runs your SQL against the database at compile time to get type information, which it injects into the program AST.
- kingkilr 13y ago
  It's 100% possible to use SQLAlchemy to do that in Python.
- pdpi 13y ago
  In that regard, while not actually an ORM per se, one of the best experiences I've ever had with SQL integration in a language was SAP's ABAP, where column types and data types are (almost?) the exact same thing.
- stonemetal 13y ago
  If you are in C# land Dapper does a good job of letting you write SQL and handle the messy put result sets in to objects part of the equation.
VeejayRampay 13y ago
ORMs are just like databases really. There's a good way and there's a bad way. It's not the ORM that causes problems, it's all about the mindset of thinking that you don't have to worry about anything because the ORM will have your back anyway. I use ActiveRecord in Rails every day and there's a lot of things it just does right. It abstracts certain things I wouldn't want to constantly have to worry about and gives me a fine-grained enough layer of control over the queries that I can actually get all the expressiveness and power I need from the records. Like they say, don't throw the baby with the bath water my friend.

nbouscal 13y ago

I don't think one is inherently superior to the other, it just depends on the data. If you have highly structured data for which integrity is mission-critical, you want to be using a RDBMS. If you have unstructured data for which throughput is mission-critical, you'll probably benefit from using a NoSQL system.

andrewflnr 13y ago

I'm sure someone has tried, but has anyone done a good job on an ORM that actually lets you select which columns to load and only selects those?

fatalmind 13y ago
here you go: http://use-the-index-luke.com/sql/join/hash-join-partial-objects#orm-partial-objects http://use-the-index-luke.com/sql/join/hash-join-partial-obj... It's really a PIA. Recently, I've learned about http://jooq.org/ http://jooq.org/ — not having checked in detail yet, it might be easier there.
riffraff 13y ago
Don't most ORM allow that? i.e. rails' ActiveRecord allows you to select columns easily in most cases: User.where(..) # all fields User.where(..).select(:name, :id) # only two of them joe.boards.select(:title) # only one in join joe.boards.pluck(:title) # only column value instead of full objects with one attribute set Though I recall it's involved for #belongs_to relations. You should also be able to setup the select as a default per-class, other than per query. I suspect, I likely didn't understand your question, could you expand it?
- andrewflnr 13y ago
  It's possible I'm just ignorant of the capabilities of most ORMs. My only real experience is with the Django ORM. AFAIK, if you select an object, it wants to make sure all the members of the object are populated. My apologies if it was a dumb question. :)
  - byroot 13y ago
    By default yes, but like most ORMs you can ask to populate only some members: https://docs.djangoproject.com/en/dev/ref/models/querysets/#only https://docs.djangoproject.com/en/dev/ref/models/querysets/#...
  - meric 13y ago
    Django has it too. https://docs.djangoproject.com/en/dev/ref/models/querysets/#defer https://docs.djangoproject.com/en/dev/ref/models/querysets/#...
barrydahlberg 13y ago
.NETs Entity Framework lets you do this using the fantastic LINQ syntax. Commonly you will say which objects to select, then give a projection into a new anonymous type with only the columns you want.
- wtetzner 13y ago
  It would be much nicer to use if C# had structural typing for the anonymous types, so you could usefully return them.
acdha 13y ago
Django offer a couple of options: .only(… field list…) .defer(… fields to fetch on demand…) https://docs.djangoproject.com/en/dev/ref/models/querysets/#only https://docs.djangoproject.com/en/dev/ref/models/querysets/#...
aidos 13y ago
SQL alchemy - it does everything the right way. http://www.sqlalchemy.org/ http://www.sqlalchemy.org/

bcoates 13y ago

The ORM I really want just takes my SQL and a connection to my database at compile or load time, and wires it up to the type system of the language I'm using. All the ones I've tried just seem to embrace the awfulness of the low-level database access APIs and are just trying to replace the good-enough DSL that is SQL with something worse.

tmcneal 13y ago
The closest I've seen an ORM come to this is Squeryl: http://squeryl.org http://squeryl.org
- oacgnol 13y ago
  Which has been superseded by Slick (http://slick.typesafe.com/ http://slick.typesafe.com/) and does exactly as the parent says.
johnpmayer 13y ago
http://www.haskell.org/haskellwiki/MetaHDBC http://www.haskell.org/haskellwiki/MetaHDBC Does exactly that. Runs your SQL against the database at compile time to get type information, which it injects into the program AST.
kingkilr 13y ago
It's 100% possible to use SQLAlchemy to do that in Python.
pdpi 13y ago
In that regard, while not actually an ORM per se, one of the best experiences I've ever had with SQL integration in a language was SAP's ABAP, where column types and data types are (almost?) the exact same thing.
stonemetal 13y ago
If you are in C# land Dapper does a good job of letting you write SQL and handle the messy put result sets in to objects part of the equation.

VeejayRampay 13y ago

ORMs are just like databases really. There's a good way and there's a bad way. It's not the ORM that causes problems, it's all about the mindset of thinking that you don't have to worry about anything because the ORM will have your back anyway. I use ActiveRecord in Rails every day and there's a lot of things it just does right. It abstracts certain things I wouldn't want to constantly have to worry about and gives me a fine-grained enough layer of control over the queries that I can actually get all the expressiveness and power I need from the records. Like they say, don't throw the baby with the bath water my friend.