FIX: Remove unsupported SQL from DB dump during restore

DB dumps might contain SQL that is unsupported in a usual Discourse DB. This removes those SQL statements during the restore of a backup to prevent errors.

lib/backup_restore/database_restorer.rb

@@ -104,15 +104,27 @@ module BackupRestore
         "CREATE SCHEMA", # PostgreSQL 11+
         "COMMENT ON SCHEMA", # PostgreSQL 11+
         "SET default_table_access_method", # PostgreSQL 12
+        "CREATE EXTENSION",
+        "COMMENT ON EXTENSION",
         "\\\\restrict",
         "\\\\unrestrict",
       ].join("|")
 
-      command = "sed -E '/^(#{unwanted_sql})/d' #{@db_dump_path}"
+      commands = [
+        "/^(#{unwanted_sql})/d;",
+        "/^CREATE FUNCTION discourse_functions/,/^\\$\\$;$/d",
+        "/^CREATE (SERVER|USER MAPPING|FOREIGN TABLE)/,/^ *\\);/d",
+      ]
+
       if BackupRestore.postgresql_major_version < 11
-        command = "#{command} | sed -E 's/^(CREATE TRIGGER.+EXECUTE) FUNCTION/\\1 PROCEDURE/'"
+        commands << "s/^(CREATE TRIGGER.+EXECUTE) FUNCTION/\\1 PROCEDURE/"
       end
-      command
+
+      <<~COMMAND
+        sed -E '
+          #{commands.join(";\n")}
+        ' #{@db_dump_path}
+      COMMAND
     end
 
     def restore_dump_command
@@ -165,6 +177,7 @@ module BackupRestore
               "SKIP_POST_DEPLOYMENT_MIGRATIONS" => "0",
               "SKIP_OPTIMIZE_ICONS" => "1",
               "DISABLE_TRANSLATION_OVERRIDES" => "1",
+              "SKIP_SEED_FU" => "1",
             },
             "rake",
             "db:migrate",

spec/fixtures/db/restore/unwanted.sql

@@ -0,0 +1,70 @@
+--
+-- PostgreSQL database dump
+--
+
+-- Dumped from database version 12.2 (Debian 12.2-2.pgdg100+1)
+-- Dumped by pg_dump version 12.2 (Debian 12.2-2.pgdg100+1)
+
+-- Started on 2020-06-15 08:06:34 UTC
+
+SET statement_timeout = 0;
+SET lock_timeout = 0;
+SET idle_in_transaction_session_timeout = 0;
+SET client_encoding = 'UTF8';
+SET standard_conforming_strings = on;
+SELECT pg_catalog.set_config('search_path', '', false);
+SET check_function_bodies = false;
+SET xmloption = content;
+SET client_min_messages = warning;
+SET row_security = off;
+
+
+    --
+-- TOC entry 198 (class 1259 OID 16585)
+-- Name: foo; Type: TABLE; Schema: public; Owner: -
+--
+
+CREATE TABLE public.foo (
+    id integer NOT NULL,
+    topic_id integer,
+    user_id integer
+);
+
+
+CREATE EXTENSION IF NOT EXISTS hstore WITH SCHEMA public;
+
+COMMENT ON EXTENSION hstore IS 'data type for storing sets of (key, value) pairs';
+
+CREATE EXTENSION IF NOT EXISTS postgres_fdw WITH SCHEMA public;
+
+COMMENT ON EXTENSION postgres_fdw IS 'foreign-data wrapper for remote PostgreSQL servers';
+
+CREATE FUNCTION discourse_functions.raise_topic_status_updates_readonly() RETURNS trigger
+  LANGUAGE plpgsql
+    AS $$
+BEGIN
+    RAISE EXCEPTION 'Discourse: topic_status_updates is read only';
+END
+$$;
+
+
+CREATE SERVER discourse_foo_fdw FOREIGN DATA WRAPPER postgres_fdw OPTIONS (
+    dbname 'discourse_foo',
+    host 'localhost',
+    port '5432'
+);
+
+CREATE USER MAPPING FOR discourse SERVER discourse_foo_fdw OPTIONS (
+    password '123',
+    "user" 'discourse'
+);
+
+CREATE FOREIGN TABLE public.foo_sso_records (
+    external_id character varying,
+    external_email character varying
+)
+SERVER discourse_foo_fdw
+OPTIONS (
+    schema_name 'public',
+    table_name 'single_sign_on_records'
+);

spec/lib/backup_restore/database_restorer_spec.rb

@@ -77,6 +77,10 @@ RSpec.describe BackupRestore::DatabaseRestorer do
         expect_restore_to_work("postgresql_15.14.sql")
       end
 
+      it "ignores unwanted SQL" do
+        expect_restore_to_work("unwanted.sql")
+      end
+
       it "detects error during restore" do
         expect { restore("error.sql", stub_migrate: false) }.to raise_error(
           BackupRestore::DatabaseRestoreError,
@@ -137,6 +141,21 @@ RSpec.describe BackupRestore::DatabaseRestorer do
           /^CREATE TRIGGER foo_user_id_readonly .+? EXECUTE FUNCTION discourse_functions.raise_foo_user_id_readonly/,
         )
       end
+
+      it "removes unwanted SQL" do
+        log = restore_and_log_output("unwanted.sql")
+
+        expect(log).to include("CREATE TABLE public.foo")
+        expect(log).not_to be_blank
+        expect(log).not_to include("CREATE EXTENSION")
+        expect(log).not_to include("COMMENT ON EXTENSION")
+        expect(log).not_to include(
+          "CREATE FUNCTION discourse_functions.raise_topic_status_updates_readonly",
+        )
+        expect(log).not_to include("CREATE SERVER")
+        expect(log).not_to include("CREATE USER")
+        expect(log).not_to include("CREATE FOREIGN TABLE")
+      end
     end
 
     describe "database connection" do