added support for Model migrations

now we have a table core.migration and each model (User, Group, Item, ItemContent and a new Migration) have its own
row in the table with a version number

added to config:
db_make_migration_if_needed and db_stop_if_migration_fails (need description yet)

winixd/models/migration.cpp

@@ -0,0 +1,133 @@
+/*
+ * This file is a part of Winix
+ * and is distributed under the 2-Clause BSD licence.
+ * Author: Tomasz Sowa <t.sowa@ttmath.org>
+ */
+
+/*
+ * Copyright (c) 2021, Tomasz Sowa
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "migration.h"
+#include "core/log.h"
+#include "finder.h"
+#include <ctime>
+
+
+namespace Winix
+{
+
+
+bool Migration::do_migration(morm::ModelConnector * model_connector, morm::Model & model)
+{
+	model.set_connector(model_connector);
+
+	std::wstring table_name;
+	model.get_table_name(table_name);
+
+	morm::Finder<Migration> finder(model_connector);
+
+	Migration migration = finder.
+		select().
+		where().
+		eq(L"table_name", table_name).
+		get();
+
+	int current_table_version = 0;
+	int old_table_version = 0;
+
+	if( migration.found() )
+	{
+		old_table_version = current_table_version = migration.table_version;
+	}
+	else
+	{
+		migration.set_save_mode(morm::Model::DO_INSERT_ON_SAVE);
+		migration.table_name = table_name;
+	}
+
+	migration.migration_date.FromTime(std::time(0));
+	bool migration_status = model.do_migration(current_table_version);
+
+	if( current_table_version != old_table_version )
+	{
+		migration.table_version = current_table_version;
+		migration_status = migration.save();
+
+		PT::Log * log = model_connector->get_logger();
+
+		if( log )
+		{
+			(*log) << PT::Log::log2 << "Migration: table " << table_name << " has been migrated to version " << current_table_version << PT::Log::logend;
+		}
+
+		if( !migration_status && log )
+		{
+			(*log) << PT::Log::log1 << "Migration: table " << table_name << " has been migrated to version " << current_table_version;
+			(*log) << " but there was a problem with saving this information in the migration table." << PT::Log::logend;
+			(*log) << "Make sure the migration table is created and save/update following record there:" << PT::Log::logend;
+			(*log) << migration << PT::Log::logend;
+		}
+	}
+
+	return migration_status;
+}
+
+
+bool Migration::do_migration(int & current_table_version)
+{
+	bool ok = true;
+
+	ok = ok && morm::Model::do_migration(current_table_version, 1, this, &Migration::do_migration_to_1);
+
+	return ok;
+}
+
+
+bool Migration::do_migration_to_1()
+{
+	// IMPROVEME
+	// what about 'create schema core'?
+	// may the name of a schema (core) should be a parameter in the config?
+
+	const char * str = R"sql(
+		create table core.migration (
+		id serial,
+		table_name varchar(255),
+		table_version int,
+		migration_date timestamp without time zone,
+		primary key(id)
+		);
+	)sql";
+
+	return db_query(str);
+}
+
+
+
+}
+