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How many connections does rails open in a recursive function?

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I have a model that has a recursive link to itself, like a linked list. If I'm writing a function like the below (pardon my syntax, Ruby is not my language of choice) to follow the chain to the end. Assuming this is part of an Active Record model and next is a foreign key to the next node, what happens behind the scenes for this function? How many separate connections to my MySQL db is Active Record opening, and how long do they stick around for?

module LinkedList
 class Node < ActiveRecord::Base

 has_one :value
 has_one :next, foreign_key: 'id' class_name: 'Source::Incident'

 def fetch_all_nodes(current_node=nil, all_nodes=nil)

 current_node = current_node ? current_node : self
 all_nodes = all_nodes ? all_nodes : [self]

 if current_node.next
 all_nodes = fetch_all_nodes(current_node.next, all_nodes << current_node)

 all_nodes
 end
 end
end

ruby-on-rails

share|improve this question

edited Mar 22 at 1:01

Sam Mullin

asked Mar 21 at 22:47

Sam MullinSam Mullin

6115

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Can you add your basic model definition as well?
  
  – Garrett Motzner
  Mar 21 at 23:06
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Fleshed it out a bit - this is meant to be a simple hypothetical example so if more detail is needed please let me know!
  
  – Sam Mullin
  Mar 22 at 1:04
  

  
  
  
  

add a comment | 

0

I have a model that has a recursive link to itself, like a linked list. If I'm writing a function like the below (pardon my syntax, Ruby is not my language of choice) to follow the chain to the end. Assuming this is part of an Active Record model and next is a foreign key to the next node, what happens behind the scenes for this function? How many separate connections to my MySQL db is Active Record opening, and how long do they stick around for?

module LinkedList
 class Node < ActiveRecord::Base

 has_one :value
 has_one :next, foreign_key: 'id' class_name: 'Source::Incident'

 def fetch_all_nodes(current_node=nil, all_nodes=nil)

 current_node = current_node ? current_node : self
 all_nodes = all_nodes ? all_nodes : [self]

 if current_node.next
 all_nodes = fetch_all_nodes(current_node.next, all_nodes << current_node)

 all_nodes
 end
 end
end

ruby-on-rails

share|improve this question

edited Mar 22 at 1:01

Sam Mullin

asked Mar 21 at 22:47

Sam MullinSam Mullin

6115

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Can you add your basic model definition as well?
  
  – Garrett Motzner
  Mar 21 at 23:06
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Fleshed it out a bit - this is meant to be a simple hypothetical example so if more detail is needed please let me know!
  
  – Sam Mullin
  Mar 22 at 1:04
  

  
  
  
  

add a comment | 

I have a model that has a recursive link to itself, like a linked list. If I'm writing a function like the below (pardon my syntax, Ruby is not my language of choice) to follow the chain to the end. Assuming this is part of an Active Record model and next is a foreign key to the next node, what happens behind the scenes for this function? How many separate connections to my MySQL db is Active Record opening, and how long do they stick around for?

module LinkedList
 class Node < ActiveRecord::Base

 has_one :value
 has_one :next, foreign_key: 'id' class_name: 'Source::Incident'

 def fetch_all_nodes(current_node=nil, all_nodes=nil)

 current_node = current_node ? current_node : self
 all_nodes = all_nodes ? all_nodes : [self]

 if current_node.next
 all_nodes = fetch_all_nodes(current_node.next, all_nodes << current_node)

 all_nodes
 end
 end
end

ruby-on-rails

share|improve this question

edited Mar 22 at 1:01

Sam Mullin

asked Mar 21 at 22:47

Sam MullinSam Mullin

6115

module LinkedList
 class Node < ActiveRecord::Base

 has_one :value
 has_one :next, foreign_key: 'id' class_name: 'Source::Incident'

 def fetch_all_nodes(current_node=nil, all_nodes=nil)

 current_node = current_node ? current_node : self
 all_nodes = all_nodes ? all_nodes : [self]

 if current_node.next
 all_nodes = fetch_all_nodes(current_node.next, all_nodes << current_node)

 all_nodes
 end
 end
end

share|improve this question

edited Mar 22 at 1:01

Sam Mullin

asked Mar 21 at 22:47

Sam MullinSam Mullin

6115

share|improve this question

edited Mar 22 at 1:01

Sam Mullin

asked Mar 21 at 22:47

Sam MullinSam Mullin

6115

asked Mar 21 at 22:47

Sam MullinSam Mullin

6115

asked Mar 21 at 22:47

Sam MullinSam Mullin

6115

2 Answers
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0

As written as a recursive function, you would have one call SQL call per node. Next is called, gets the related nodes, and caches the value. (You can reload it if needed). As far as I can tell this implementation ends up with a single object per database record. If you ended up looking up an object that you already had stored, that would cause more objects, and more database lookups, but Rails has a query cache, so that can reduce such lookups.

You could have all_nodes instead return a lazy enumerator, and then if you don't end up inspecting the entire tail, you'd only have one call per node visited, and you could handle potentially infinite (or even looping) lists.

share|improve this answer

answered Mar 22 at 2:08

Garrett MotznerGarrett Motzner

823315

add a comment | 

0

ActiveRecord uses ActiveRecord::ConnectionAdapters::ConnectionPool to connect to your datastore which has a default pool of 5 connections. So, at most, each instance of Rails/ActiveRecord will use a max number of database connections as the configured connection pool size.

share|improve this answer

answered Mar 22 at 3:02

Scott BartellScott Bartell

2,11621735

add a comment | 

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0

As written as a recursive function, you would have one call SQL call per node. Next is called, gets the related nodes, and caches the value. (You can reload it if needed). As far as I can tell this implementation ends up with a single object per database record. If you ended up looking up an object that you already had stored, that would cause more objects, and more database lookups, but Rails has a query cache, so that can reduce such lookups.

You could have all_nodes instead return a lazy enumerator, and then if you don't end up inspecting the entire tail, you'd only have one call per node visited, and you could handle potentially infinite (or even looping) lists.

share|improve this answer

answered Mar 22 at 2:08

Garrett MotznerGarrett Motzner

823315

add a comment | 

0

As written as a recursive function, you would have one call SQL call per node. Next is called, gets the related nodes, and caches the value. (You can reload it if needed). As far as I can tell this implementation ends up with a single object per database record. If you ended up looking up an object that you already had stored, that would cause more objects, and more database lookups, but Rails has a query cache, so that can reduce such lookups.

You could have all_nodes instead return a lazy enumerator, and then if you don't end up inspecting the entire tail, you'd only have one call per node visited, and you could handle potentially infinite (or even looping) lists.

share|improve this answer

answered Mar 22 at 2:08

Garrett MotznerGarrett Motzner

823315

add a comment | 

As written as a recursive function, you would have one call SQL call per node. Next is called, gets the related nodes, and caches the value. (You can reload it if needed). As far as I can tell this implementation ends up with a single object per database record. If you ended up looking up an object that you already had stored, that would cause more objects, and more database lookups, but Rails has a query cache, so that can reduce such lookups.

You could have all_nodes instead return a lazy enumerator, and then if you don't end up inspecting the entire tail, you'd only have one call per node visited, and you could handle potentially infinite (or even looping) lists.

share|improve this answer

answered Mar 22 at 2:08

Garrett MotznerGarrett Motzner

823315

share|improve this answer

answered Mar 22 at 2:08

Garrett MotznerGarrett Motzner

823315

answered Mar 22 at 2:08

Garrett MotznerGarrett Motzner

823315

answered Mar 22 at 2:08

Garrett MotznerGarrett Motzner

823315

0

ActiveRecord uses ActiveRecord::ConnectionAdapters::ConnectionPool to connect to your datastore which has a default pool of 5 connections. So, at most, each instance of Rails/ActiveRecord will use a max number of database connections as the configured connection pool size.

share|improve this answer

answered Mar 22 at 3:02

Scott BartellScott Bartell

2,11621735

add a comment | 

0

ActiveRecord uses ActiveRecord::ConnectionAdapters::ConnectionPool to connect to your datastore which has a default pool of 5 connections. So, at most, each instance of Rails/ActiveRecord will use a max number of database connections as the configured connection pool size.

share|improve this answer

answered Mar 22 at 3:02

Scott BartellScott Bartell

2,11621735

add a comment | 

ActiveRecord uses ActiveRecord::ConnectionAdapters::ConnectionPool to connect to your datastore which has a default pool of 5 connections. So, at most, each instance of Rails/ActiveRecord will use a max number of database connections as the configured connection pool size.

share|improve this answer

answered Mar 22 at 3:02

Scott BartellScott Bartell

2,11621735

share|improve this answer

answered Mar 22 at 3:02

Scott BartellScott Bartell

2,11621735

answered Mar 22 at 3:02

Scott BartellScott Bartell

2,11621735

answered Mar 22 at 3:02

Scott BartellScott Bartell

2,11621735