Add preprocessor to remove \restrict and \unrestrict pragmas

those where introduced in newer versions of pg_dump and are not valid
SQL, so they need to be removed before the SQL file can be parsed.

newer versions of rails will handle this (see:
rails/rails#55510), but in order to keep this
library working with older versions of rails we need to remove those
ourselves.

Author: Jell

CHANGELOG.md

@@ -1,5 +1,8 @@
 ## [Unreleased]
 
+- Add preprocessors config that allows applying text transforms to the input before parsing
+- Add preprocessor to remove `\restrict` and `\unrestrict` pragmas that appeared in newer versions of pg_dump
+
 ## [0.5.0] - 2025-08-04
 
 - Upgrade pg_query to 6.1 to add support for latest mac OS version

README.md

@@ -9,6 +9,7 @@ Say good-bye to those pesky diffs you get between coworkers!
 
 By default, it will:
 
+* remove `\restrict` and `\unrestrict` pragmas
 * Inline primary key declarations
 * Inline SERIAL type declarations
 * Inline table constraints
@@ -27,6 +28,8 @@ As an example, the task will transform this raw `structure.sql`:
 <summary>Click to expand</summary>
 
 ```sql
+\restrict 1234
+
 --
 -- Name: pgcrypto; Type: EXTENSION; Schema: -; Owner: -
 --
@@ -261,6 +264,10 @@ If you want to configure which transforms to use, you can configure the library
 
 ```ruby
 Rails.application.configure do
+  config.activerecord_pg_format_db_structure.preprocessors = [
+    Preprocessors::RemoveRestrictPragmas
+  ]
+
   config.activerecord_pg_format_db_structure.transforms = [
     ActiveRecordPgFormatDbStructure::Transforms::RemoveCommentsOnExtensions,
     ActiveRecordPgFormatDbStructure::Transforms::RemoveDefaultsSetCommands,
@@ -271,7 +278,7 @@ Rails.application.configure do
     ActiveRecordPgFormatDbStructure::Transforms::InlineConstraints,
     ActiveRecordPgFormatDbStructure::Transforms::MoveIndicesAfterCreateTable,
     ActiveRecordPgFormatDbStructure::Transforms::GroupAlterTableStatements,
-    ActiveRecordPgFormatDbStructure::Transforms::SortTableColumns,
+    ActiveRecordPgFormatDbStructure::Transforms::SortTableColumns
   ]
 
   config.activerecord_pg_format_db_structure.deparser = ActiveRecordPgFormatDbStructure::Deparser
@@ -287,6 +294,13 @@ structure = File.read("db/structure.sql")
 formatted = ActiveRecordPgFormatDbStructure::Formatter.new.format(structure)
 File.write("db/structure.sql", formatted)
 ```
+## Preprocessors
+
+### RemoveRestrictPragmas
+
+Remove `\restrict` and `\unrestrict` pragmas that were added in newer
+versions of `pg_dump`, since they are not valid SQL syntax and
+therefore prevent parsing the file as SQL.
 
 ## Transformers
 

lib/activerecord-pg-format-db-structure.rb

@@ -4,6 +4,7 @@
 
 require_relative "activerecord-pg-format-db-structure/deparser"
 require_relative "activerecord-pg-format-db-structure/statement_appender"
+require_relative "activerecord-pg-format-db-structure/preprocessors/remove_restrict_pragmas"
 require_relative "activerecord-pg-format-db-structure/transforms/remove_comments_on_extensions"
 require_relative "activerecord-pg-format-db-structure/transforms/inline_serials"
 require_relative "activerecord-pg-format-db-structure/transforms/inline_primary_keys"
@@ -16,6 +17,10 @@
 require_relative "activerecord-pg-format-db-structure/transforms/sort_table_columns"
 
 module ActiveRecordPgFormatDbStructure
+  DEFAULT_PREPROCESSORS = [
+    Preprocessors::RemoveRestrictPragmas
+  ].freeze
+
   DEFAULT_TRANSFORMS = [
     Transforms::RemoveCommentsOnExtensions,
     Transforms::RemoveDefaultsSetCommands,

lib/activerecord-pg-format-db-structure/formatter.rb

@@ -6,19 +6,25 @@
 module ActiveRecordPgFormatDbStructure
   # Formats & normalizes in place the given SQL string
   class Formatter
-    attr_reader :transforms, :deparser, :statement_appender
+    attr_reader :preprocessors, :transforms, :deparser, :statement_appender
 
     def initialize(
+      preprocessors: DEFAULT_PREPROCESSORS,
       transforms: DEFAULT_TRANSFORMS,
       deparser: DEFAULT_DEPARSER,
       statement_appender: DEFAULT_STATEMENT_APPENDER
     )
+      @preprocessors = preprocessors
       @transforms = transforms
       @deparser = deparser
       @statement_appender = statement_appender
     end
 
     def format(source)
+      preprocessors.each do |preprocessor|
+        preprocessor.new(source).preprocess!
+      end
+
       raw_statements = PgQuery.parse(source).tree.stmts
 
       transforms.each do |transform|

lib/activerecord-pg-format-db-structure/preprocessors/base.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+require "pg_query"
+
+module ActiveRecordPgFormatDbStructure
+  module Preprocessors
+    # :nodoc:
+    class Base
+      attr_reader :source
+
+      def initialize(source)
+        @source = source
+      end
+    end
+  end
+end

lib/activerecord-pg-format-db-structure/preprocessors/remove_restrict_pragmas.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+require_relative "base"
+
+module ActiveRecordPgFormatDbStructure
+  module Preprocessors
+    # Inline non-foreign key constraints into table declaration
+    class RemoveRestrictPragmas < Base
+      def preprocess!
+        source.gsub!(/^(\\restrict .*)$/, '')
+        source.gsub!(/^(\\unrestrict .*)$/, '')
+      end
+    end
+  end
+end

lib/activerecord-pg-format-db-structure/railtie.rb

@@ -4,6 +4,7 @@ module ActiveRecordPgFormatDbStructure
   # Setup for Rails
   class Railtie < Rails::Railtie
     config.activerecord_pg_format_db_structure = ActiveSupport::OrderedOptions.new
+    config.activerecord_pg_format_db_structure.preprocessors = DEFAULT_PREPROCESSORS.dup
     config.activerecord_pg_format_db_structure.transforms = DEFAULT_TRANSFORMS.dup
     config.activerecord_pg_format_db_structure.deparser = DEFAULT_DEPARSER
     config.activerecord_pg_format_db_structure.statement_appender = DEFAULT_STATEMENT_APPENDER

spec/activerecord-pg-format-db-structure/formatter_spec.rb

@@ -2,7 +2,7 @@
 
 RSpec.describe ActiveRecordPgFormatDbStructure::Formatter do
   describe "#format" do
-    it "does a good job by default" do
+   it "does a good job by default" do
       formatter = described_class.new
 
       source = +<<~SQL
@@ -229,5 +229,40 @@
         ;
       SQL
     end
+
+    it "handles pg_dump's \restrict commands" do
+
+      formatter = described_class.new
+
+      source = +<<~SQL
+        \\restrict 1234
+
+        --
+        -- Name: comments; Type: TABLE; Schema: public; Owner: -
+        --
+
+        CREATE TABLE public.comments (
+            id bigserial PRIMARY KEY,
+            user_id bigint NOT NULL,
+            post_id bigint NOT NULL,
+            created_at timestamp(6) without time zone NOT NULL,
+            updated_at timestamp(6) without time zone NOT NULL
+        );
+
+        \\unrestrict 1234
+      SQL
+
+      expect(formatter.format(source)).to eq(<<~SQL)
+        -- Name: comments; Type: TABLE;
+
+        CREATE TABLE public.comments (
+            id bigserial PRIMARY KEY,
+            post_id bigint NOT NULL,
+            user_id bigint NOT NULL,
+            created_at timestamp(6) NOT NULL,
+            updated_at timestamp(6) NOT NULL
+        );
+      SQL
+    end
   end
 end

spec/activerecord-pg-format-db-structure/preprocessors/remove_restrict_pragmas_spec.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+RSpec.describe ActiveRecordPgFormatDbStructure::Preprocessors::RemoveRestrictPragmas do
+  describe "#preprocess!" do
+    it 'removes \restrict and \unrestrict pragmas' do
+
+      source = +<<~SQL
+        \\restrict 1234
+
+        CREATE TABLE public.comments (
+            id bigint NOT NULL,
+            user_id bigint NOT NULL,
+            post_id bigint NOT NULL,
+            created_at timestamp(6) without time zone NOT NULL,
+            updated_at timestamp(6) without time zone NOT NULL
+        );
+
+        \\unrestrict 1234
+      SQL
+
+      ActiveRecordPgFormatDbStructure::Preprocessors::RemoveRestrictPragmas.new(
+        source
+      ).preprocess!
+
+      expect(source).to eq(<<~SQL)
+
+
+        CREATE TABLE public.comments (
+            id bigint NOT NULL,
+            user_id bigint NOT NULL,
+            post_id bigint NOT NULL,
+            created_at timestamp(6) without time zone NOT NULL,
+            updated_at timestamp(6) without time zone NOT NULL
+        );
+
+
+      SQL
+    end
+  end
+end