Suggestion for Rails 4

When I began learning rails I found it frustrating that array and active record relation objects could not be queried in the same fashion as database tables. Before too much confusion let me explain.

When I want something from a database table I simply write something like: Product.where(:color=>‘black’) NOW, if I put a .to_sql after that statement I see something like “SELECT “styles”.* FROM “styles” WHERE “styles”.“color” = ‘black’”

So clearly, rails is magically converting that friendly statement into something more meaningful to the backend. That’s fantastic and makes my life wonderful.

So here’s my problem… after running the query I am returned an active record relation, which let’s say is called @products. Now, let’s say I want to further break that list of products into products that are big and small. This would require one of two things… either I must hit the database twice being more selective, or I must iterate over @products using a block and such ruby magic as collect/map/select/etc…

To me neither of the above is a great option, and I must admit while learning ruby on rails this was one of the biggest stumbling blocks for me, and one that has produced a massive amount of stackoverflow headaches for many others.

My suggestion to rails developers is to make rails more accessible to beginners by allowing programmers to apply the same simplicity of writing an active record query to querying an active record relation object or array of model objects.

For example, I want to now take @products and say:

@products.where(:size=>“small”) and have this converted automagically by rails to the appropriate statement @products.select{|product| product.size == ‘small’}

I suppose this could work if rails were to query the object type first before performing the query. Is the object type an array or active record relation, and is it in the expected format (collection of appropriate objects)? If it is, then treat it as a virtual table and instead of performing an sql query, hit it with a select block, etc.

I know understanding the underlying ruby code is good, and at times would be preferable to using active record style commands… but for new users getting off the ground, I think having both options would be beneficial. Also, I feel it would be more consistency to the framework generally.

I have also posted this at reddit http://www.reddit.com/r/rails/comments/12kyho/suggestion_for_rails_4_what_are_pros_and_cons/

When I began learning rails I found it frustrating that array and active
record relation objects could not be queried in the same fashion as database
tables. Before too much confusion let me explain.

When I want something from a database table I simply write something like:
Product.where(:color=>'black') NOW, if I put a .to_sql after that statement
I see something like "SELECT \"styles\".* FROM \"styles\" WHERE
\"styles\".\"color\" = 'black'"

So clearly, rails is magically converting that friendly statement into
something more meaningful to the backend. That's fantastic and makes my life
wonderful.

So here's my problem.. after running the query I am returned an active
record relation, which let's say is called @products. Now, let's say I want
to further break that list of products into products that are big and small.
This would require one of two things.. either I must hit the database twice
being more selective, or I must iterate over @products using a block and
such ruby magic as collect/map/select/etc...

To me neither of the above is a great option, and I must admit while
learning ruby on rails this was one of the biggest stumbling blocks for me,
and one that has produced a massive amount of stackoverflow headaches for
many others.

My suggestion to rails developers is to make rails more accessible to
beginners by allowing programmers to apply the same simplicity of writing an
active record query to querying an active record relation object or array of
model objects.

For example, I want to now take @products and say:

@products.where(:size=>"small")

That should work, does it not for you?

Colin

and have this converted automagically by

Well, it does, but it hits the DB again.

Basically it just chains on to the previous db query, but still runs a new one… it doesn’t query the active record relation object. Also, you cannot query an array of objects… say @products = Product.all … then say @products.where(:color=>“black”) … You will get NoMethodError: undefined method `where’ for #Array:0x00000003918108

Basically it just chains on to the previous db query, but still runs a new
one.. it doesn't query the active record relation object. Also, you cannot
query an array of objects.. say @products = Product.all ... then say
@products.where(:color=>"black") .. You will get NoMethodError: undefined
method `where' for #<Array:0x00000003918108>

If you're running the code in the console, it hits the db immediately. But
if it's in the actual application, it won't hit the db until you need to
access the records
which usually happens when you call each or map or collect on the active
relation object. So given your code, if you want to get all black and
small objects, you can

@products = Product.where(color: 'black')
@products = @products.where(size: 'small')

these two lines will not actually create the product records and will not
yet hit the db until you want to iterate each of the products.

As for calling Product.all, I checked the api and it doesn't explicitly say
that #all returns an array. But if you know that beforehand, you shouldn't
have any issues
with chaining methods.

Jim, Thanks for that.

What I mean is I want small and large black products attached to two separate variables, say @blacksmall and @blacklarge… both separated out from @products which initially resulted from the Product.where(:color => 'black) query. I know it’s a stupid example, but I’m just wanting that functionality, and think it would be an improvement in rails to enable using active record queries on objects that are arrays of objects as they are represented in the table. If rails treats table rows as model objects why not treat a collection of model objects in the same way, allowing the same dsl for access/limiting what’s within the collection.

Thanks

Abram ha scritto:

Jim, Thanks for that.

What I mean is I want small and large black products attached to two
separate variables, say @blacksmall and @blacklarge.. both separated out
from @products which initially resulted from the Product.where(:color =>
'black) query. I know it's a stupid example, but I'm just wanting that
functionality, and think it would be an improvement in rails to enable
using active record queries on objects that are arrays of objects as
they are represented in the table. If rails treats table rows as model
objects why not treat a collection of model objects in the same way,
allowing the same dsl for access/limiting what's within the collection.

I'm not an expert of performances, but maybe databases like postgres or mysql are faster than other solutions to retrieve data from a complex query, so the solution to run a new query is better than filtering a ruby collection, which can be simple but can already be very very complex (think to db like openstreetmaps and you want to calculate a path...)

Jim, Thanks for that.

What I mean is I want small and large black products attached to two
separate variables, say @blacksmall and @blacklarge.. both separated out
from @products which initially resulted from the Product.where(:color =>
'black) query. I know it's a stupid example, but I'm just wanting that
functionality, and think it would be an improvement in rails to enable using
active record queries on objects that are arrays of objects as they are
represented in the table. If rails treats table rows as model objects why
not treat a collection of model objects in the same way, allowing the same
dsl for access/limiting what's within the collection.

Once you convert to an array then you have lost the knowledge about
the database. Just keep everthing as activerecord collections and all
will be well. Rails will defer running queries until it has to as far
as it can in order to keep everything reasonably efficient.

So
@products = Product.where :color => 'black'
@smallproducts = @products.where :size => 'small'
@largeproducts = @products.where :size => 'large'

What is the problem?

Colin

An interesting idea, but by the time you’ve written enough code to support things like joins you’ve basically recreated an RDBMS inside of ActiveRecord. The alternative would be to support only a subset, but that seems worse than no support at all…

–Matt Jones

Matt,

I appreciate your answer… a good explanation :slight_smile:

I’ll drop it now

Abram