Re: [Rails-core] Method to find inside of relation
On Nov 22, 2014, at 5:03 PM, Sunny Juneja jr.su...@gmail.com wrote:
Hey everyone,
I've obviously done a bad job of explaining this :). Let me try to elaborate.
Suppose I've ran xyz = Model.where(attribute: true)
A SQL query is created and executed. The results are saved to xyz as an
ActiveRecord_Relation. The query looks something like this:
SELECT models.* FROM models WHERE models.attribute = ’t'
This is a place that people frequently get confused - doing this only runs the
query in the REPL, where the result has `inspect` called on it for printing.
Try this in the REPL to see the difference:
xyz = Model.where(attribute: true); nil
This will set `xyz` but not trigger the query. Any subsequent code that
attempts to access elements of `xyz` will trigger the query - so `to_a`, or
`each`, etc.
Note that some methods will trigger a different query - for instance, calling
`xyz.first` will perform a query with `LIMIT 1` if the records haven’t been
loaded yet.
If I run xyz.find_by(attribute2: false), a nw SQL query is created and
executed and it will hit the database again. The query looks something like
this:
SELECT models.* FROM models WHERE models.attribute = 't' AND
models.attribute2 = 'f' LIMIT 1
On the other hand, the proposed find_in_relation is a method on an
ActiveRecord_Relation that doesn't hit the database and searches the relation
in memory.
If I type xyz.find_in_relation(attribute2: false), no new sql query is
created and it will not touch the database. The code would be equivalent to
running:
xyz.select { |x| x.attribute2 == false }
Ideally, find_in_relation would return another ActiveRecord_Relation.
`Relation` is intended to build queries. The results of in-memory filtering are
not going to make that possible, in general, short of flattening everything to
a giant `id IN (?)` clause.
The only use case I can see for something like this is when some of the
attributes you’re filtering by aren’t DB columns but instead are model methods.
For that case, `select` seems
to make the in-memory filtering aspect clearer.
—Matt Jones
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Re: [Rails-core] Method to find inside of relation
Hey everyone,
I've obviously done a bad job of explaining this :). Let me try to
elaborate.
Suppose I've ran xyz = Model.where(attribute: true)
A SQL query is created and executed. The results are saved to xyz as an
ActiveRecord_Relation. The query looks something like this:
SELECT models.* FROM models WHERE models.attribute = 't'
If I run xyz.find_by(attribute2: false), a new SQL query is created and
executed and it will hit the database again. The query looks something like
this:
SELECT models.* FROM models WHERE models.attribute = 't' AND
models.attribute2 = 'f' LIMIT 1
On the other hand, the proposed find_in_relation is a method on an
ActiveRecord_Relation that *doesn't hit the database* and searches the
relation in memory.
If I type xyz.find_in_relation(attribute2: false), no new sql query is
created and it will not touch the database. The code would be equivalent to
running:
xyz.select { |x| x.attribute2 == false }
Ideally, find_in_relation would return another ActiveRecord_Relation.
Sunny Juneja
On Sunday, November 16, 2014 6:32:15 AM UTC-8, Matt jones wrote:
On Nov 14, 2014, at 4:05 PM, Sunny Juneja jr.s...@gmail.com javascript:
wrote:
Hey, I ran into this problem fairly recently. I needed to get a large
number of records and search them over and over again on different
attributes. I found myself writing code that looked a lot like this.
records = Model.where(...)
records.select { |r| r.attribute1 == attribute1 r.attribute2 ==
attribute2 ... }
Although this is a simple case, I found myself rewriting this over and
over again.
Is there anything equivalent that might fit the form
records = Model.where(...)
records.find_in_relation(attribute1: attribute1, attribute2: attribute2,
attribute3, ...)
Was just wondering if there was a place for such syntactical sugar or a
desire to add some. If there is too simple a change to warrant, I
understand.
If attribute1, attribute2, etc are database columns then I think `where`
is the same as your `find_in_relation`…
records = Model.where(...)
records.where(attribute1: attribute1, attribute2: attribute2, attribute3,
…)
Can you explain further what `find_in_relation` is intended to do
differently?
—Matt Jones
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Re: [Rails-core] Method to find inside of relation
On Nov 14, 2014, at 4:05 PM, Sunny Juneja jr.su...@gmail.com wrote:
Hey, I ran into this problem fairly recently. I needed to get a large number
of records and search them over and over again on different attributes. I
found myself writing code that looked a lot like this.
records = Model.where(...)
records.select { |r| r.attribute1 == attribute1 r.attribute2 == attribute2
... }
Although this is a simple case, I found myself rewriting this over and over
again.
Is there anything equivalent that might fit the form
records = Model.where(...)
records.find_in_relation(attribute1: attribute1, attribute2: attribute2,
attribute3, ...)
Was just wondering if there was a place for such syntactical sugar or a
desire to add some. If there is too simple a change to warrant, I understand.
If attribute1, attribute2, etc are database columns then I think `where` is the
same as your `find_in_relation`…
records = Model.where(...)
records.where(attribute1: attribute1, attribute2: attribute2, attribute3, …)
Can you explain further what `find_in_relation` is intended to do differently?
—Matt Jones
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Re: [Rails-core] Method to find inside of relation
You should be able to use find_by and pass in a hash with attributes and
respective values to find a record.
Please take a look at the docs for find_by on the api guides.
Carlos Antonio da Silva - via celular
On Nov 14, 2014 7:44 PM, Sunny Juneja jr.su...@gmail.com wrote:
Hey, I ran into this problem fairly recently. I needed to get a large
number of records and search them over and over again on different
attributes. I found myself writing code that looked a lot like this.
records = Model.where(...)
records.select { |r| r.attribute1 == attribute1 r.attribute2 ==
attribute2 ... }
Although this is a simple case, I found myself rewriting this over and
over again.
Is there anything equivalent that might fit the form
records = Model.where(...)
records.find_in_relation(attribute1: attribute1, attribute2: attribute2,
attribute3, ...)
Was just wondering if there was a place for such syntactical sugar or a
desire to add some. If there is too simple a change to warrant, I
understand.
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Ruby on Rails: Core group.
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