examples

ClickHouse JS client examples

Examples located directly in examples directory should work with both Node.js and Web versions of the client. The only difference will be in the import statement - @clickhouse/client vs @clickhouse/client-web.

Node.JS-specific examples are located in the examples/node directory.

Overview

We aim to cover various scenarios of client usage with these examples. You should be able to run any of these examples, see How to run section below.

If something is missing, or you found a mistake in one of these examples, please open an issue or a pull request, or contact us.

General usage

• url_configuration.ts - client configuration using the URL parameters.
• clickhouse_settings.ts - ClickHouse settings on the client side, both global and per operation.
• ping.ts - sample checks if the server can be reached.
• abort_request.ts - cancelling an outgoing request or a read-only query.
• cancel_query.ts - cancelling a potentially long-running query on the server side.
• long_running_queries_timeouts.ts - avoiding timeout errors for long-running queries (two different approaches).
• read_only_user.ts - an example of using the client with a read-only user, with possible read-only user limitations highlights.
• basic_tls.ts - (Node.js only) using certificates for basic TLS authentication.
• mutual_tls.ts - (Node.js only) using certificates for mutual TLS authentication.

Creating tables

• create_table_single_node.ts - creating a table on a single-node deployment.
• create_table_on_premise_cluster.ts - creating a table on a multi-node deployment when macro values are required to be present in the DDL for Replicated tables.
• create_table_cloud.ts - creating a table in ClickHouse Cloud.

Inserting data

• array_json_each_row.ts - a simple insert of an array of values using JSONEachRow format.
• insert_data_formats_overview.ts - an overview of available data formats for inserting data.
• async_insert.ts - server-side batching using async inserts; the client will be waiting for a written batch ack.
• async_insert_without_waiting.ts - server-side batching using async inserts; the client will not be waiting for a written batch ack. This is a bit more advanced async insert example simulating an event listener.
• insert_exclude_columns.ts - inserting into specific columns only, or excluding certain columns from the INSERT statement.
• insert_from_select.ts - INSERT FROM SELECT example, using the command method instead of the default insert.
• insert_into_different_db.ts - inserting data into a table in a different database, regardless of the database provided in the connection settings.
• insert_decimals.ts - inserting decimal values into ClickHouse using JSONEachRow format.
• insert_js_dates.ts - an example of inserting objects that contain JS Date into ClickHouse.
• insert_file_stream_csv.ts - (Node.js only) stream a CSV file into ClickHouse.
• insert_file_stream_ndjson.ts - (Node.js only) stream a NDJSON file into ClickHouse.
• insert_file_stream_parquet.ts - (Node.js only) stream a Parquet file into ClickHouse.
• stream_created_from_array_raw.ts - (Node.js only) converting the string input into a stream and sending it to ClickHouse; in this scenario, the base input is a CSV string.
• insert_values_and_functions.ts - generating an INSERT INTO ... VALUES statement that uses a combination of values and function calls.
• insert_ephemeral_columns.ts - inserting data into a table that has ephemeral columns.

Selecting data

• select_json_each_row.ts - simple select of the data in the JSONEachRow format.
• select_data_formats_overview.ts - an overview of all available data formats for select queries.
• select_json_with_metadata.ts - select result as a JSON object with query metadata.
• query_with_parameter_binding.ts - query parameter binding example.
• select_parquet_as_file.ts - (Node.js only) select data from ClickHouse and save it as a Parquet file. This example can be adjusted to save the data in other formats, such as CSV/TSV/TabSeparated, by changing the format in the query.
• select_streaming_json_each_row.ts - (Node.js only) streaming JSON* formats from ClickHouse and processing it with on('data') event.
• select_streaming_json_each_row_for_await.ts - (Node.js only) similar to select_streaming_json_each_row.ts, but using the for await loop syntax.
• select_streaming_text_line_by_line.ts - (Node.js only) streaming text formats from ClickHouse and processing it line by line. In this example, CSV format is used.

Special cases

• default_format_setting.ts - sending queries using exec method without a FORMAT clause; the default format will be set from the client settings.
• session_id_and_temporary_tables.ts - creating a temporary table, which requires a session_id to be passed to the server.
• session_level_commands.ts - using SET commands, memorized for the specific session_id.

How to run

Prerequisites

Environment requirements for all examples:

• Node.js 18+
• NPM
• Docker Compose

Run ClickHouse in Docker from the root folder of this repository:

docker-compose up -d

This will create two local ClickHouse instances: one with plain authentication and one that requires TLS.

Any example except create_table_*

Change the working directory to examples and install the dependencies:

cd examples
npm i

Then, you should be able to run the sample programs, for example:

ts-node --transpile-only array_json_each_row.ts

TLS examples

You will need to add server.clickhouseconnect.test to your /etc/hosts to make it work, as self-signed certificates are used in these examples.

Execute the following command to add the required /etc/hosts entry:

sudo -- sh -c "echo 127.0.0.1 server.clickhouseconnect.test >> /etc/hosts"

After that, you should be able to run the examples:

ts-node --transpile-only node/basic_tls.ts
ts-node --transpile-only node/mutual_tls.ts

On-premise cluster examples

For create_table_on_premise_cluster.ts, you will need to start a local cluster first.

Run this command from the root folder of this repository:

docker-compose -f docker-compose.cluster.yml up -d

Now, you should be able to run the example:

ts-node --transpile-only create_table_on_premise_cluster.ts

ClickHouse Cloud examples

• for *_cloud.ts examples, Docker containers are not required, but you need to set some environment variables first:

export CLICKHOUSE_URL=https://<your-clickhouse-cloud-hostname>:8443
export CLICKHOUSE_PASSWORD=<your-clickhouse-cloud-password>

You can obtain these credentials in the ClickHouse Cloud console (check the docs for more information).

Cloud examples assume that you are using the default user and database.

Run one of the Cloud examples:

ts-node --transpile-only create_table_cloud.ts