1.0.0

Formal stable release milestone with many improvements and some breaking changes.

Major new features overview:

• Advanced TypeScript support for query + ResultSet
• URL configuration

From now on, the client will follow the official semantic versioning guidelines.

Deprecated API

The following configuration parameters are marked as deprecated:

• The host configuration parameter is deprecated; use url instead.
• additional_headers configuration parameter is deprecated; use http_headers instead.

The client will log a warning if any of these parameters are used. However, it is still allowed to use host instead of url and additional_headers instead of http_headers for now; this deprecation is not supposed to break the existing code.

These parameters will be removed in the next major release (2.0.0).

See the "New features" section for more details.

Breaking changes in 1.0.0

• compression.response is now disabled by default in the client configuration options, as it cannot be used with readonly=1 users, and it was not clear from the ClickHouse error message what exact client option was causing the failing query in this case. If you'd like to continue using response compression, you should explicitly enable it in the client configuration.
• As the client now supports parsing URL configuration, you should specify pathname as a separate configuration option (as it would be considered as the database otherwise).
• (TypeScript only) ResultSet and Row are now more strictly typed, according to the format used during the query call.
• (TypeScript only) Both Node.js and Web versions now uniformly export correct ClickHouseClient and ClickHouseClientConfigOptions types specific to each implementation. Exported ClickHouseClient now does not have a Stream type parameter, as it was unintended to expose it there. NB: you should still use the createClient factory function provided in the package.

New features in 1.0.0

Advanced TypeScript support for query + ResultSet

The client will now try its best to figure out the shape of the data based on the DataFormat literal specified to the query call, as well as which methods are allowed to be called on the ResultSet.

Live demo (see the full description below):

Screencast.from.2024-03-09.08-10-26.webm

Complete reference:

Format	ResultSet.json<T>()	ResultSet.stream<T>()	Stream data	Row.json<T>()
JSON	ResponseJSON<T>	never	never	never
JSONObjectEachRow	Record<string, T>	never	never	never
All other JSON*EachRow	Array<T>	Stream<Array<Row<T>>>	Array<Row<T>>	T
CSV/TSV/CustomSeparated/Parquet	never	Stream<Array<Row<T>>>	Array<Row<T>>	never

By default, T (which represents JSONType) is still unknown. However, considering the JSONObjectsEachRow example, prior to 1.0.0, you had to specify the entire type hint, including the shape of the data, manually:

type Data = { foo: string }

const resultSet = await client.query({
  query: 'SELECT * FROM my_table',
  format: 'JSONObjectsEachRow',
})

// pre-1.0.0, `resultOld` has type Record<string, Data>
const resultOld = resultSet.json<Record<string, Data>>()
// const resultOld = resultSet.json<Data>() // incorrect! The type hint should've been `Record<string, Data>` here.

// 1.0.0, `resultNew` also has type Record<string, Data>; the client inferred that it has to be a Record from the format literal.
const resultNew = resultSet.json<Data>()

This is even more handy in the case of streaming on the Node.js platform:

const resultSet = await client.query({
  query: 'SELECT * FROM my_table',
  format: 'JSONEachRow',
})

// pre-1.0.0
// `streamOld` was just a regular Node.js Stream.Readable
const streamOld = resultSet.stream()
// `rows` were `any`, needed an explicit type hint
streamNew.on('data', (rows: Row[]) => {
  rows.forEach((row) => {
    // without an explicit type hint to `rows`, calling `forEach` and other array methods resulted in TS compiler errors
    const t = row.text
    const j = row.json<Data>() // `j` needed a type hint here, otherwise, it's `unknown`
  })
})

// 1.0.0
// `streamNew` is now StreamReadable<T> (Node.js Stream.Readable with a bit more type hints);
// type hint for the further `json` calls can be added here (and removed from the `json` calls)
const streamNew = resultSet.stream<Data>()
// `rows` are inferred as an Array<Row<Data, "JSONEachRow">> instead of `any`
streamNew.on('data', (rows) => {
  // `row` is inferred as Row<Data, "JSONEachRow">
  rows.forEach((row) => {
    // no explicit type hints required, you can use `forEach` straight away and TS compiler will be happy
    const t = row.text
    const j = row.json() // `j` will be of type Data
  })
})

// async iterator now also has type hints
//Similarly to the `on(data)` example above, `rows` are inferred as Array<Row<Data, "JSONEachRow">>
for await (const rows of streamNew) {
  // `row` is inferred as Row<Data, "JSONEachRow">
  rows.forEach((row) => {
    const t = row.text
    const j = row.json() // `j` will be of type Data
  })
}

Calling ResultSet.stream is not allowed for specific data formats, such as JSON and JSONObjectsEachRow (unlike JSONEachRow and the rest of JSON*EachRow, these formats return a single object). In these cases, the client throws an error. However, it was previously not reflected on the type level; now, calling stream on these formats will result in a TS compiler error. For example:

const resultSet = await client.query('SELECT * FROM table', {
  format: 'JSON',
})
const stream = resultSet.stream() // `stream` is `never`

Calling ResultSet.json also does not make sense on CSV and similar "raw" formats, and the client throws. Again, now, it is typed properly:

const resultSet = await client.query('SELECT * FROM table', {
  format: 'CSV',
})
// `json` is `never`; same if you stream CSV, and call `Row.json` - it will be `never`, too.
const json = resultSet.json()

Currently, there is one known limitation: as the general shape of the data and the methods allowed for calling are inferred from the format literal, there might be situations where it will fail to do so, for example:

// assuming that `queryParams` has `JSONObjectsEachRow` format inside
async function runQuery(
  queryParams: QueryParams,
): Promise<Record<string, Data>> {
  const resultSet = await client.query(queryParams)
  // type hint here will provide a union of all known shapes instead of a specific one
  // inferred shapes: Data[] | ResponseJSON<Data> | Record<string, Data>
  return resultSet.json<Data>()
}

In this case, as it is likely that you already know the desired format in advance (otherwise, returning a specific shape like Record<string, Data> would've been incorrect), consider helping the client a bit:

async function runQuery(
  queryParams: QueryParams,
): Promise<Record<string, Data>> {
  const resultSet = await client.query({
    ...queryParams,
    format: 'JSONObjectsEachRow',
  })
  // TS understands that it is a Record<string, Data> now
  return resultSet.json<Data>()
}

If you are interested in more details, see the related test (featuring a great ESLint plugin expect-types) in the client package.

URL configuration

• Added url configuration parameter. It is intended to replace the deprecated host, which was already supposed to be passed as a valid URL.
• It is now possible to configure most of the client instance parameters with a URL. The URL format is http[s]://[username:password@]hostname:port[/database][?param1=value1&param2=value2]. In almost every case, the name of a particular parameter reflects its path in the config options interface, with a few exceptions. The following parameters are supported:

Parameter	Type
pathname	an arbitrary string.
application_id	an arbitrary string.
session_id	an arbitrary string.
request_timeout	non-negative number.
max_open_connections	non-negative number, greater than zero.
compression_request	boolean. See below [1].
compression_response	boolean.
log_level	allowed values: OFF, TRACE, DEBUG, INFO, WARN, ERROR.
keep_alive_enabled	boolean.
clickhouse_setting_* or ch_*	see below [2].
http_header_*	see below [3].
(Node.js only) keep_alive_idle_socket_ttl	non-negative number.

[1] For booleans, valid values will be true/1 and false/0.

[2] Any parameter prefixed with clickhouse_setting_ or ch_ will have this prefix removed and the rest added to client's clickhouse_settings. For example, ?ch_async_insert=1&ch_wait_for_async_insert=1 will be the same as:

createClient({
  clickhouse_settings: {
    async_insert: 1,
    wait_for_async_insert: 1,
  },
})

Note: boolean values for clickhouse_settings should be passed as 1/0 in the URL.

[3] Similar to [2], but for the http_header configuration. For example, ?http_header_x-clickhouse-auth=foobar will be an equivalent of:

createClient({
  http_headers: {
    'x-clickhouse-auth': 'foobar',
  },
})

Important: URL will always overwrite the hardcoded values and a warning will be logged in this case.

Currently not supported via URL:

• log.LoggerClass
• (Node.js only) tls_ca_cert, tls_cert, tls_key.

See also: URL configuration example.

Performance

• (Node.js only) Improved performance when decoding the entire set of rows with streamable JSON formats (such as JSONEachRow or JSONCompactEachRow) by calling the ResultSet.json() method. NB: The actual streaming performance when consuming the ResultSet.stream() hasn't changed. Only the ResultSet.json() method used a suboptimal stream processing in some instances, and now ResultSet.json() just consumes the same stream transformer provided by the ResultSet.stream() method (see #253 for more details).

Miscellaneous

• Added http_headers configuration parameter as a direct replacement for additional_headers. Functionally, it is the same, and the change is purely cosmetic, as we'd like to leave an option to implement a TCP connection open in the future.