Add backup creation

docker/init-invidious-db.sh

@@ -1,6 +1,8 @@
 #!/bin/bash
 set -eou pipefail
 
+psql --username "$POSTGRES_USER" --dbname "$POSTGRES_DB" -c "CREATE SCHEMA IF NOT EXISTS backup"
+
 psql --username "$POSTGRES_USER" --dbname "$POSTGRES_DB" < config/sql/channels.sql
 psql --username "$POSTGRES_USER" --dbname "$POSTGRES_DB" < config/sql/videos.sql
 psql --username "$POSTGRES_USER" --dbname "$POSTGRES_DB" < config/sql/channel_videos.sql

src/invidious/database/migrator.cr

@@ -10,10 +10,18 @@ class Invidious::Database::Migrator
     versions = load_versions
 
     ran_migration = false
+    backed_up = false
     load_migrations.sort_by(&.version)
       .each do |migration|
         next if versions.includes?(migration.version)
 
+      
+        if !backed_up
+          puts "New migration(s) found: creating database backup"
+          back_up_database
+          backed_up = true
+        end  
+
         puts "Running migration: #{migration.class.name}"
         migration.migrate
         ran_migration = true
@@ -46,4 +54,33 @@ class Invidious::Database::Migrator
       )
     SQL
   end
+
+  private def back_up_database
+    table_names_request = <<-SQL
+      SELECT tablename FROM pg_catalog.pg_tables
+      WHERE schemaname = 'public'
+    SQL
+    
+    table_names = @db.query_all(table_names_request, as: String)
+
+    table_names.try &.each do |name|
+      copy_table(name)
+    end  
+  end  
+
+  private def copy_table(table_name : String)
+    @db.exec <<-SQL
+      CREATE TABLE IF NOT EXISTS backup.#{table_name} (
+        id bigserial PRIMARY KEY
+      )
+    SQL
+
+    @db.exec("DROP TABLE backup.#{table_name}")
+  
+    @db.exec <<-SQL
+      SELECT * INTO backup.#{table_name}
+      FROM public.#{table_name}
+    SQL
+  end  
+
 end