Add topological sorting for dumped views using TSort

.github/workflows/ci.yml

@@ -30,12 +30,9 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ["2.7", "3.0", "3.1", "3.2"]
+        ruby: ["3.1", "3.2"]
         rails: ["6.1", "7.0"]
         continue-on-error: [false]
-        exclude:
-          - ruby: "3.2"
-            rails: "6.1"
 
     runs-on: ubuntu-latest
 

Gemfile

@@ -3,9 +3,9 @@ source "https://rubygems.org"
 # Specify your gem's dependencies in scenic.gemspec
 gemspec
 
-rails_version = ENV.fetch("RAILS_VERSION", "6.1")
+rails_version = ENV.fetch("RAILS_VERSION", "7.0")
 
-rails_constraint = if rails_version == "master"
+rails_constraint = if rails_version == "main"
   {github: "rails/rails"}
 else
   "~> #{rails_version}.0"

lib/scenic/schema_dumper.rb

@@ -3,6 +3,34 @@
 module Scenic
   # @api private
   module SchemaDumper
+    # A hash to do topological sort
+    class TSortableHash < Hash
+      include TSort
+
+      alias_method :tsort_each_node, :each_key
+      def tsort_each_child(node, &)
+        fetch(node).each(&)
+      end
+    end
+
+    # Query for the dependencies between views
+    DEPENDENT_SQL = <<~SQL.freeze
+      SELECT distinct dependent_ns.nspname AS dependent_schema
+      , dependent_view.relname AS dependent_view
+      , source_ns.nspname AS source_schema
+      , source_table.relname AS source_table
+      FROM pg_depend
+      JOIN pg_rewrite ON pg_depend.objid = pg_rewrite.oid
+      JOIN pg_class as dependent_view ON pg_rewrite.ev_class = dependent_view.oid
+      JOIN pg_class as source_table ON pg_depend.refobjid = source_table.oid
+      JOIN pg_namespace dependent_ns ON dependent_ns.oid = dependent_view.relnamespace
+      JOIN pg_namespace source_ns ON source_ns.oid = source_table.relnamespace
+      WHERE dependent_ns.nspname = ANY (current_schemas(false)) AND source_ns.nspname = ANY (current_schemas(false))
+      AND source_table.relname != dependent_view.relname
+      AND source_table.relkind IN ('m', 'v') AND dependent_view.relkind IN ('m', 'v')
+      ORDER BY dependent_view.relname;
+    SQL
+
     def tables(stream)
       super
       views(stream)
@@ -22,11 +50,47 @@ def views(stream)
     private
 
     def dumpable_views_in_database
-      @dumpable_views_in_database ||= Scenic.database.views.reject do |view|
-        ignored?(view.name)
+      @ordered_dumpable_views_in_database ||= begin
+        existing_views = Scenic.database.views.reject do |view|
+          ignored?(view.name)
+        end
+
+        tsorted_views(existing_views.map(&:name)).map do |view_name|
+          existing_views.find do |ev|
+            ev.name == view_name || ev.name == view_name.split(".").last
+          end
+        end.compact
       end
     end
 
+    # When dumping the views, their order must be topologically
+    # sorted to take into account dependencies
+    def tsorted_views(views_names)
+      views_hash = TSortableHash.new
+
+      ::Scenic.database.execute(DEPENDENT_SQL).each do |relation|
+        source_v = [
+          relation["source_schema"],
+          relation["source_table"]
+        ].compact.join(".")
+        dependent = [
+          relation["dependent_schema"],
+          relation["dependent_view"]
+        ].compact.join(".")
+        views_hash[dependent] ||= []
+        views_hash[source_v] ||= []
+        views_hash[dependent] << source_v
+        views_names.delete(relation["source_table"])
+        views_names.delete(relation["dependent_view"])
+      end
+
+      # after dependencies, there might be some views left
+      # that don't have any dependencies
+      views_names.sort.each { |v| views_hash[v] ||= [] }
+
+      views_hash.tsort
+    end
+
     unless ActiveRecord::SchemaDumper.private_instance_methods(false).include?(:ignored?)
       # This method will be present in Rails 4.2.0 and can be removed then.
       def ignored?(table_name)

scenic.gemspec

@@ -22,7 +22,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "database_cleaner"
   spec.add_development_dependency "rake"
   spec.add_development_dependency "rspec", ">= 3.3"
-  spec.add_development_dependency "pg", "~> 0.19"
+  spec.add_development_dependency "pg"
   spec.add_development_dependency "pry"
   spec.add_development_dependency "ammeter", ">= 1.1.3"
   spec.add_development_dependency "yard"

spec/scenic/schema_dumper_spec.rb

@@ -69,6 +69,22 @@ class SearchInAHaystack < ActiveRecord::Base
 
       Search.connection.drop_view :"scenic.searches"
     end
+
+    it "sorts dependency order when views exist in a non-public schema" do
+      Search.connection.execute("CREATE SCHEMA IF NOT EXISTS scenic; SET search_path TO public, scenic")
+      Search.connection.execute("CREATE VIEW scenic.apples AS SELECT 1;")
+      Search.connection.execute("CREATE VIEW scenic.bananas AS SELECT 2;")
+      Search.connection.execute("CREATE OR REPLACE VIEW scenic.apples AS SELECT * FROM scenic.bananas;")
+      stream = StringIO.new
+
+      ActiveRecord::SchemaDumper.dump(Search.connection, stream)
+      views = stream.string.lines.grep(/create_view/).map do |view_line|
+        view_line.match('create_view "(?<name>.*)"')[:name]
+      end
+      expect(views).to eq(%w[scenic.bananas scenic.apples])
+
+      Search.connection.execute("DROP SCHEMA IF EXISTS scenic CASCADE; SET search_path TO public")
+    end
   end
 
   it "handles active record table name prefixes and suffixes" do