feat: support sql dump

Add `ActiveRecord::CockroachDB::DatabaseTasks#structure_dump`
method. Which itself allows for the related rake tasks (ex:
`rake db:schema:dump`).

We are doing that using the `SHOW CREATE ...` family of queries
in cockroach and some local logic to sort out what is needed.
See https://www.cockroachlabs.com/docs/v23.1/show-create.html.

Most tests are grouped in one to avoid dumping many time. This
clutters a bit lisibility in case of failure, but this part of
the code should not change often, so we'd rather have velocity
rather than lisibility.

Fixes #2

Author: BuonOmo

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Ongoing
 
+- Add support for sql dump in rake tasks (#273).
 - Add support for table optimize hints (#266).
 
 ## 7.0.2 - 2023-05-23

lib/active_record/connection_adapters/cockroachdb/database_tasks.rb

@@ -5,7 +5,43 @@ module ConnectionAdapters
     module CockroachDB
       class DatabaseTasks < ActiveRecord::Tasks::PostgreSQLDatabaseTasks
         def structure_dump(filename, extra_flags=nil)
-          raise "db:structure:dump is unimplemented. See https://github.com/cockroachdb/activerecord-cockroachdb-adapter/issues/2"
+          if extra_flags
+            raise "No flag supported yet, please raise an issue if needed. " \
+              "https://github.com/cockroachdb/activerecord-cockroachdb-adapter/issues/new"
+          end
+
+          case ActiveRecord.dump_schemas
+          when :all, String
+            raise  "Custom schemas are not supported in CockroachDB. " \
+              "See https://github.com/cockroachdb/cockroach/issues/26443."
+          when :schema_search_path
+            if configuration_hash[:schema_search_path]
+              raise  "Custom schemas are not supported in CockroachDB. " \
+                "See https://github.com/cockroachdb/cockroach/issues/26443."
+            end
+          end
+
+          conn = ActiveRecord::Base.connection
+          File.open(filename, "w") do |file|
+            %w(SCHEMAS TYPES).each do |object_kind|
+              ActiveRecord::Base.connection.execute("SHOW CREATE ALL #{object_kind}").each_row { file.puts _1 }
+            end
+
+            ignore_tables = ActiveRecord::SchemaDumper.ignore_tables.to_set
+
+            conn.execute("SHOW CREATE ALL TABLES").each_row do |(sql)|
+              if sql.start_with?("CREATE")
+                table_name = sql[/CREATE TABLE (?:.*?\.)?\"?(.*?)[\" ]/, 1]
+                next if ignore_tables.member?(table_name)
+              elsif sql.start_with?("ALTER")
+                table_name = sql[/ALTER TABLE (?:.*?\.)?\"?(.*?)[\" ]/, 1]
+                ref_table_name = sql[/REFERENCES (?:.*?\.)?\"?(.*?)[\" ]/, 1]
+                next if ignore_tables.member?(table_name) || ignore_tables.member?(ref_table_name)
+              end
+
+              file.puts sql
+            end
+          end
         end
 
         def structure_load(filename, extra_flags=nil)

test/cases/tasks/cockroachdb_rake_test.rb

@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "active_record/tasks/database_tasks"
+require "active_record/connection_adapters/cockroachdb/database_tasks"
+
+module ActiveRecord
+  class CockroachDBStructureDumpTest < ActiveRecord::TestCase
+    def setup
+      @configuration = {
+        "adapter"  => "cockroachdb",
+        "database" => "my-app-db"
+      }
+      @filename = "/tmp/awesome-file.sql"
+      FileUtils.touch(@filename)
+    end
+
+    def teardown
+      FileUtils.rm_f(@filename)
+    end
+
+    def test_structure_dump
+      assert_equal "", File.read(@filename)
+      File.write(@filename, "NOT TODAY\n")
+
+      config = @configuration.dup
+      config["database"] = ARTest.config["connections"]["cockroachdb"]["arunit"]["database"]
+
+      begin
+        ActiveRecord::Base.connection.execute(<<~SQL)
+          CREATE TYPE IF NOT EXISTS status AS ENUM ('open', 'closed', 'inactive');
+        SQL
+        assert_called(
+          ActiveRecord::SchemaDumper,
+          :ignore_tables,
+          returns: ["accounts", "articles"]
+        ) do
+          ActiveRecord::Tasks::DatabaseTasks.structure_dump(config, @filename)
+
+          read = File.read(@filename)
+        end
+      ensure
+        ActiveRecord::Base.connection.execute(<<~SQL)
+          DROP TYPE IF EXISTS status;
+        SQL
+      end
+
+      read = File.read(@filename)
+      refute read.include?("NOT TODAY"), "The dump file previous content was not overwritten"
+      assert read.include?("CREATE SCHEMA public;"), "Schemas are not dumped"
+      assert read.include?("CREATE TYPE public.status AS ENUM ('open', 'closed', 'inactive');"), "Types are not dumped"
+      assert read.include?("CREATE TABLE public.schema_migrations"), "No dump done"
+      refute read.include?("CREATE TABLE public.articles ("), "\"articles\" table should be ignored"
+      refute read.include?("CREATE TABLE public.accounts ("), "\"accounts\" table should be ignored"
+    end
+  end
+end