.hash_tree returning NoMethodError: undefined method `[]=' for nil:NilClass

[kurko]

I have a weird problem here. I added some nodes and suddenly I can't use Taxonomy.hash_tree anymore.

I thought, "ok, given I just started out, I'll just delete everything and start over", but then what if this issue happens when I go to production?

In fact, after starting over and recreating the nodes, I haven't got the error so far.

Do you have any idea what this could be?

Thanks!

Data

Here, everything's ok.

irb(main):003:0> Company.first.taxonomies.all
  Company Load (0.6ms)  SELECT "companies".* FROM "companies" LIMIT 1
  Taxonomy Load (0.3ms)  SELECT "taxonomies".* FROM "taxonomies" WHERE "taxonomies"."store_id" = 1
=> [#<Taxonomy id: 15, name: "a", parent_id: nil, store_id: 1, created_at: "2013-01-08 01:14:34", updated_at: "2013-01-08 01:14:34">, 
#<Taxonomy id: 16, name: "aa", parent_id: 15, store_id: 1, created_at: "2013-01-08 01:14:37", updated_at: "2013-01-08 01:14:37">, 
#<Taxonomy id: 17, name: "aaa", parent_id: 16, store_id: 1, created_at: "2013-01-08 01:14:40", updated_at: "2013-01-08 01:14:40">, 
#<Taxonomy id: 18, name: "b", parent_id: nil, store_id: 1, created_at: "2013-01-08 01:14:45", updated_at: "2013-01-08 01:14:45">, 
#<Taxonomy id: 19, name: "bb", parent_id: 18, store_id: 1, created_at: "2013-01-08 01:14:48", updated_at: "2013-01-08 01:14:48">, 
#<Taxonomy id: 20, name: "aaa2", parent_id: 16, store_id: 1, created_at: "2013-01-08 01:14:59", updated_at: "2013-01-08 01:14:59">, 
#<Taxonomy id: 21, name: "aaaa", parent_id: 20, store_id: 1, created_at: "2013-01-08 01:59:28", updated_at: "2013-01-08 01:59:28">, 
#<Taxonomy id: 22, name: "aaaa2", parent_id: 20, store_id: 1, created_at: "2013-01-08 01:59:34", updated_at: "2013-01-08 01:59:34">, 
#<Taxonomy id: 23, name: "aaa3", parent_id: 20, store_id: 1, created_at: "2013-01-08 01:59:38", updated_at: "2013-01-08 01:59:38">, 
#<Taxonomy id: 24, name: "a", parent_id: 9, store_id: 1, created_at: "2013-01-08 02:34:03", updated_at: "2013-01-08 02:34:03">, 
#<Taxonomy id: 25, name: "a", parent_id: 9, store_id: 1, created_at: "2013-01-08 02:34:08", updated_at: "2013-01-08 02:34:08">]

Problematic hash_tree

Here, the error.

irb(main):006:0> Company.first.taxonomies.hash_tree
  Company Load (0.7ms)  SELECT "companies".* FROM "companies" LIMIT 1
  Taxonomy Load (0.7ms)  SELECT "taxonomies".* FROM "taxonomies" INNER JOIN (
 SELECT descendant_id, MAX(generations) as depth
 FROM "taxonomy_hierarchies"
 GROUP BY descendant_id

 ) AS generation_depth
 ON "taxonomies".id = generation_depth.descendant_id WHERE "taxonomies"."store_id" = 1 ORDER BY generation_depth.depth
NoMethodError: undefined method `[]=' for nil:NilClass
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/bundler/gems/closure_tree-7bf33728b625/lib/closure_tree/acts_as_tree.rb:398:in `block in build_hash_tree'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/activerecord-3.2.9/lib/active_record/relation/delegation.rb:6:in `each'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/activerecord-3.2.9/lib/active_record/relation/delegation.rb:6:in `each'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/bundler/gems/closure_tree-7bf33728b625/lib/closure_tree/acts_as_tree.rb:393:in `build_hash_tree'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/bundler/gems/closure_tree-7bf33728b625/lib/closure_tree/acts_as_tree.rb:94:in `hash_tree'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/activerecord-3.2.9/lib/active_record/relation/delegation.rb:14:in `block in hash_tree'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/activerecord-3.2.9/lib/active_record/relation.rb:241:in `block in scoping'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/activerecord-3.2.9/lib/active_record/scoping.rb:98:in `with_scope'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/activerecord-3.2.9/lib/active_record/relation.rb:241:in `scoping'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/activerecord-3.2.9/lib/active_record/relation/delegation.rb:14:in `hash_tree'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/activerecord-3.2.9/lib/active_record/associations/collection_proxy.rb:100:in `method_missing'
        from (irb):6
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/railties-3.2.9/lib/rails/commands/console.rb:47:in `start'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/railties-3.2.9/lib/rails/commands/console.rb:8:in `start'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/zeus-0.12.0/lib/zeus/rails.rb:117:in `console'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/zeus-0.12.0/lib/zeus.rb:105:in `block in command'
... 8 levels...
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/zeus-0.12.0/lib/zeus.rb:61:in `go'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/zeus-0.12.0/lib/zeus.rb:67:in `block (3 levels) in go'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/zeus-0.12.0/lib/zeus.rb:67:in `fork'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/zeus-0.12.0/lib/zeus.rb:67:in `block (2 levels) in go'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/zeus-0.12.0/lib/zeus.rb:63:in `each'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/zeus-0.12.0/lib/zeus.rb:63:in `block in go'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/zeus-0.12.0/lib/zeus.rb:61:in `loop'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/zeus-0.12.0/lib/zeus.rb:61:in `go'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/zeus-0.12.0/lib/zeus.rb:67:in `block (3 levels) in go'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/zeus-0.12.0/lib/zeus.rb:67:in `fork'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/zeus-0.12.0/lib/zeus.rb:67:in `block (2 levels) in go'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/zeus-0.12.0/lib/zeus.rb:63:in `each'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/zeus-0.12.0/lib/zeus.rb:63:in `block in go'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/zeus-0.12.0/lib/zeus.rb:61:in `loop'
        from /Users/kurko/.rbenv/versions/1.9.3-p194-perf/lib/ruby/gems/1.9.1/gems/zeus-0.12.0/lib/zeus.rb:61:in `go'
        from -e:1:in `<main>'

[mceachen]

Do you have a db backup from when it was broken? If you can share the result of:

SELECT id, parent_id, name
FROM taxonomies

We can shove the data into a spec and try to reproduce the issue.

[mceachen]

ping

[kurko]

Hey @mceachen, pong

Sorry, it has been a busy week. I destroyed all records and started from scratch. I got no errors so far.

I will try reproducing the issue again in the next couple of days.

Thanks.

[mceachen]

OK, then, I don't think we can move forward here. Feel free to reopen this issue or open a new one if you find this happen again. With a data dump we'll be able to quickly get the to bottom of whatever happened.

If you've got a multithreaded app that's creating lots of hierarchies, I'm working on integrating monogamy with closure_tree to make sure the transaction boundaries are correct. You may have been bitten by duplicative rows, but I can't even guess without your data when it was broken.

[mceachen]

I looked at this more in the light of #146, and the issue here is that you are incanting hash_tree against a relation object from a non-closure-tree model. ActiveRecord added .hash_tree for any collection of your tree model, but .hash_tree can't span multiple roots.

If you don't mind multiple selects:

Company.first.taxonomies.map(&:hash_tree).reduce(&:merge)

[kurko]

👍 2 years later, but still relevant 😊

[mceachen]

did you try the .map.reduce?

[dhurba87]

@mceachen
.map.reduce works but the query is too much slow. :(
Updating version > 6.0 worked in my case.