Rails sql issue with a simple where statement - sql

Question

I am trying to get a very simple statement working.
Node.where("nodeid = ?", nstart).select('id')
Results in
Parameters: {"utf8"=>"✓", "authenticity_token"=>"WpSpzLzaFUx8QgFbwEfygQUkkqvbUgZl8Hh0UxJvT8E=", "edge"=>{"kind"=>"IsA", "start_id"=>"blabla", "end_id"=>"bliblib", "property1"=>"bloblbo"}, "commit"=>"Create Edge"}
(0.0ms) begin transaction
Node Load (0.1ms) SELECT "nodes".* FROM "nodes" WHERE "nodes"."id" = ? LIMIT 1 [["id", 0]]
CACHE (0.0ms) SELECT "nodes".* FROM "nodes" WHERE "nodes"."id" = ? LIMIT 1 [["id", 0]]
(0.0ms) rollback transaction
It should be just a ´select nodes.id from nodes where nodeid = blabla´ The limit doesn't matter.
However if I add .first.
Node.where("nodeid = ?", nstart).select('id').first
I get
Parameters: {"utf8"=>"✓", "authenticity_token"=>"WpSpzLzaFUx8QgFbwEfygQUkkqvbUgZl8Hh0UxJvT8E=", "edge"=>{"kind"=>"IsA", "start_id"=>"blabla", "end_id"=>"bliblib", "property1"=>"bloblbo"}, "commit"=>"Create Edge"}
Node Load (0.1ms) SELECT "nodes"."id" FROM "nodes" WHERE (nodeid = 'blabla') ORDER BY "nodes"."id" ASC LIMIT 1
Node Load (0.1ms) SELECT "nodes"."id" FROM "nodes" WHERE (nodeid = 'bliblib') ORDER BY "nodes"."id" ASC LIMIT 1
(0.0ms) begin transaction
Node Load (0.1ms) SELECT "nodes".* FROM "nodes" WHERE "nodes"."id" = ? LIMIT 1 [["id", 0]]
CACHE (0.0ms) SELECT "nodes".* FROM "nodes" WHERE "nodes"."id" = ? LIMIT 1 [["id", 0]]
(0.1ms) rollback transaction
The first select now is what it should be but the follow up is again like before and seems to determine the eventual return value (because it doesn't work either). I just want the id when I only know the nodeid which basically is the name of the node.
What is going on in Rails here?

Answer 1

If you just want the id value you could do this
Node.where("nodeid = ?", nstart).limit(1).pluck(:id).first
This would return 1 integer with the value
EDIT:
ok scratch that, i guess you don't really need to use limit so a simple first would just do
Node.where("nodeid = ?", nstart).first[:id]
or
Node.where("nodeid = ?", nstart).first.id

Answer 2

You're making a query:
Node.where("nodeid = ?", nstart).select('id')
will return an array of objects (or empty array if there's no suitable records) *not array actually. Activerecord::Relation
If you use 'first' like Mohammad AbuShady told:
Node.where("nodeid = ?", nstart).select('id').first
you get an object (or nil if there's no record)
If you want an integer id value, you can get it from the object
Node.where("nodeid = ?", nstart).first.id
select('id') tells active record not to retrieve all the fields in the table, just 'id'