discourse/lib/migration/table_dropper.rb

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require_dependency 'migration/base_dropper'
module Migration
class Migration::TableDropper < BaseDropper
def self.delayed_drop(table_name:, after_migration:, delay: nil, on_drop: nil, after_drop: nil)
validate_table_name(table_name)
TableDropper.new(
table_name, nil, after_migration, delay, on_drop, after_drop
).delayed_drop
end
def self.delayed_rename(old_name:, new_name:, after_migration:, delay: nil, on_drop: nil, after_drop: nil)
validate_table_name(old_name)
validate_table_name(new_name)
TableDropper.new(
old_name, new_name, after_migration, delay, on_drop, after_drop
).delayed_drop
end
def self.read_only_table(table_name)
create_readonly_function(table_name)
DB.exec <<~SQL
CREATE TRIGGER #{readonly_trigger_name(table_name)}
BEFORE INSERT OR UPDATE OR DELETE OR TRUNCATE
ON #{table_name}
FOR EACH STATEMENT
EXECUTE PROCEDURE #{readonly_function_name(table_name)};
SQL
end
private
def initialize(old_name, new_name, after_migration, delay, on_drop, after_drop)
super(after_migration, delay, on_drop, after_drop)
@old_name = old_name
@new_name = new_name
end
def droppable?
builder = DB.build(<<~SQL)
SELECT 1
FROM INFORMATION_SCHEMA.TABLES
/*where*/
LIMIT 1
SQL
builder.where(table_exists(":new_name")) if @new_name.present?
builder.where("table_schema = 'public'")
.where(table_exists(":old_name"))
.where(previous_migration_done)
.exec(old_name: @old_name,
new_name: @new_name,
delay: "#{@delay} seconds",
after_migration: @after_migration) > 0
end
def table_exists(table_name_placeholder)
<<~SQL
EXISTS(
SELECT 1
FROM INFORMATION_SCHEMA.TABLES
WHERE table_schema = 'public' AND
table_name = #{table_name_placeholder}
)
SQL
end
def execute_drop!
DB.exec("DROP TABLE IF EXISTS #{@old_name}")
DB.exec <<~SQL
DROP FUNCTION IF EXISTS #{BaseDropper.readonly_function_name(@old_name)} CASCADE;
SQL
end
end
end