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-rw-r--r--config/initializers/postgresql_cte.rb132
1 files changed, 132 insertions, 0 deletions
diff --git a/config/initializers/postgresql_cte.rb b/config/initializers/postgresql_cte.rb
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index 00000000000..7f0df8949db
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+++ b/config/initializers/postgresql_cte.rb
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+# Adds support for WITH statements when using PostgreSQL. The code here is taken
+# from https://github.com/shmay/ctes_in_my_pg which at the time of writing has
+# not been pushed to RubyGems. The license of this repository is as follows:
+#
+# The MIT License (MIT)
+#
+# Copyright (c) 2012 Dan McClain
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
+module ActiveRecord
+ class Relation
+ class Merger # :nodoc:
+ def normal_values
+ NORMAL_VALUES + [:with]
+ end
+ end
+ end
+end
+
+module ActiveRecord::Querying
+ delegate :with, to: :all
+end
+
+module ActiveRecord
+ class Relation
+ # WithChain objects act as placeholder for queries in which #with does not have any parameter.
+ # In this case, #with must be chained with #recursive to return a new relation.
+ class WithChain
+ def initialize(scope)
+ @scope = scope
+ end
+
+ # Returns a new relation expressing WITH RECURSIVE
+ def recursive(*args)
+ @scope.with_values += args
+ @scope.recursive_value = true
+ @scope
+ end
+ end
+
+ def with_values
+ @values[:with] || []
+ end
+
+ def with_values=(values)
+ raise ImmutableRelation if @loaded
+ @values[:with] = values
+ end
+
+ def recursive_value=(value)
+ raise ImmutableRelation if @loaded
+ @values[:recursive] = value
+ end
+
+ def recursive_value
+ @values[:recursive]
+ end
+
+ def with(opts = :chain, *rest)
+ if opts == :chain
+ WithChain.new(spawn)
+ elsif opts.blank?
+ self
+ else
+ spawn.with!(opts, *rest)
+ end
+ end
+
+ def with!(opts = :chain, *rest) # :nodoc:
+ if opts == :chain
+ WithChain.new(self)
+ else
+ self.with_values += [opts] + rest
+ self
+ end
+ end
+
+ def build_arel
+ arel = super()
+
+ build_with(arel) if @values[:with]
+
+ arel
+ end
+
+ def build_with(arel)
+ with_statements = with_values.flat_map do |with_value|
+ case with_value
+ when String
+ with_value
+ when Hash
+ with_value.map do |name, expression|
+ case expression
+ when String
+ select = Arel::Nodes::SqlLiteral.new "(#{expression})"
+ when ActiveRecord::Relation, Arel::SelectManager
+ select = Arel::Nodes::SqlLiteral.new "(#{expression.to_sql})"
+ end
+ Arel::Nodes::As.new Arel::Nodes::SqlLiteral.new("\"#{name}\""), select
+ end
+ when Arel::Nodes::As
+ with_value
+ end
+ end
+
+ unless with_statements.empty?
+ if recursive_value
+ arel.with :recursive, with_statements
+ else
+ arel.with with_statements
+ end
+ end
+ end
+ end
+end