clickhouse: add to README.md and examples database creation

database/clickhouse/README.md

@@ -23,3 +23,4 @@
 * Clickhouse cluster mode is not officially supported, since it's not tested right now, but you can try enabling `schema_migrations` table replication by specifying a `x-cluster-name`:
   * When `x-cluster-name` is specified, `x-migrations-table-engine` also should be specified. See the docs regarding [replicated table engines](https://clickhouse.tech/docs/en/engines/table-engines/mergetree-family/replication/#table_engines-replication).
   * When `x-cluster-name` is specified, only the `schema_migrations` table is replicated across the cluster. You still need to write your migrations so that the application tables are replicated within the cluster.
+* If you want to create database inside the migration, you should know, that table which will manage migrations `schema-migrations table` will be in `deafault` table, so you can't use `USE <database_name>` inside migration. In this case you may not specify the database in the connection string (example you can find [here](examples/migrations/003_create_database.up.sql))

database/clickhouse/examples/migrations/003_create_database.down.sql

@@ -0,0 +1,10 @@
+DROP TABLE IF EXISTS driver_ratings;
+DROP TABLE IF EXISTS user_ratings;
+DROP TABLE IF EXISTS orders;
+DROP TABLE IF EXISTS driver_ratings_queue;
+DROP TABLE IF EXISTS user_ratings_queue;
+DROP TABLE IF EXISTS orders_queue;
+DROP VIEW IF EXISTS user_ratings_queue_mv;
+DROP VIEW IF EXISTS driver_ratings_queue_mv;
+DROP VIEW IF EXISTS orders_queue_mv;
+DROP DATABASE IF EXISTS analytics;

database/clickhouse/examples/migrations/003_create_database.up.sql

@@ -0,0 +1,81 @@
+CREATE DATABASE IF NOT EXISTS analytics;
+
+CREATE TABLE IF NOT EXISTS analytics.driver_ratings(
+    rate UInt8,
+    userID Int64,
+    driverID String,
+    orderID String,
+    inserted_time DateTime DEFAULT now()
+) ENGINE = MergeTree
+PARTITION BY driverID
+ORDER BY (inserted_time);
+
+CREATE TABLE analytics.driver_ratings_queue(
+    rate UInt8,
+    userID Int64,
+    driverID String,
+    orderID String
+) ENGINE = Kafka
+SETTINGS kafka_broker_list = 'broker:9092',
+    kafka_topic_list = 'driver-ratings',
+    kafka_group_name = 'rating_readers',
+    kafka_format = 'Avro',
+    kafka_max_block_size = 1048576;
+
+CREATE MATERIALIZED VIEW analytics.driver_ratings_queue_mv TO analytics.driver_ratings AS
+SELECT rate, userID, driverID, orderID
+FROM analytics.driver_ratings_queue;
+
+CREATE TABLE IF NOT EXISTS analytics.user_ratings(
+    rate UInt8,
+    userID Int64,
+    driverID String,
+    orderID String,
+    inserted_time DateTime DEFAULT now()
+) ENGINE = MergeTree
+    PARTITION BY userID
+    ORDER BY (inserted_time);
+
+CREATE TABLE analytics.user_ratings_queue(
+    rate UInt8,
+    userID Int64,
+    driverID String,
+    orderID String
+) ENGINE = Kafka
+SETTINGS kafka_broker_list = 'broker:9092',
+    kafka_topic_list = 'user-ratings',
+    kafka_group_name = 'rating_readers',
+    kafka_format = 'JSON',
+    kafka_max_block_size = 1048576;
+
+CREATE MATERIALIZED VIEW analytics.user_ratings_queue_mv TO analytics.user_ratings AS
+SELECT rate, userID, driverID, orderID
+FROM analytics.user_ratings_queue;
+
+CREATE TABLE IF NOT EXISTS analytics.orders(
+    from_place String,
+    to_place String,
+    userID Int64,
+    driverID String,
+    orderID String,
+    inserted_time DateTime DEFAULT now()
+) ENGINE = MergeTree
+    PARTITION BY driverID
+    ORDER BY (inserted_time);
+
+CREATE TABLE analytics.orders_queue(
+    from_place String,
+    to_place String,
+    userID Int64,
+    driverID String,
+    orderID String
+) ENGINE = Kafka
+SETTINGS kafka_broker_list = 'broker:9092',
+    kafka_topic_list = 'orders',
+    kafka_group_name = 'order_readers',
+    kafka_format = 'Avro',
+    kafka_max_block_size = 1048576;
+
+CREATE MATERIALIZED VIEW analytics.orders_queue_mv TO orders AS
+SELECT from_place, to_place, userID, driverID, orderID
+FROM analytics.orders_queue;