clickhouse-js-node-coding

name

clickhouse-js-node-coding

description

Write idiomatic application code with the ClickHouse Node.js client (`@clickhouse/client`). Use this skill whenever a user is *building* against the Node.js client - configuring the client, pinging, inserting rows in JSON or raw formats, selecting and parsing results, binding query parameters, managing sessions and temporary tables, working with data types or customizing JSON parsing. Do NOT use for browser/Web client code.

ClickHouse Node.js Client - Coding

Reference: https://clickhouse.com/docs/integrations/javascript

Warning Node.js runtime only. This skill covers the @clickhouse/client package running in a Node.js runtime exclusively - including Next.js Node runtime API routes, React Server Components, Server Actions, and standard Node.js processes. Do not apply this skill to browser client components, Web Workers, Next.js Edge runtime, Cloudflare Workers, or any usage of @clickhouse/client-web. For browser/edge environments, the correct package is @clickhouse/client-web.

---

How to Use This Skill

1. Match the user's intent to a row in the Task Index below and read the corresponding reference file before writing code. After reading it, scan any Answer checklist in that reference and make sure the final answer covers each relevant item; those checklists capture details users usually need but are easy to omit in short answers.
2. Always import from @clickhouse/client (never @clickhouse/client-web) and create a client with createClient({ url }) or rely on supported defaults when appropriate. Close it with await client.close() preferably when it's no longer needed or during graceful shutdown for global resources.
3. Prefer JSONEachRow for typical row inserts/selects unless the user has already chosen another format or is streaming raw bytes (CSV / TSV / Parquet - see examples/node/performance/). Note on clickhouse_settings: settings passed to createClient are defaults for every request; they can be overridden per-call by passing clickhouse_settings directly to insert(), query(), or command(). Always mention this when the user configures settings at the client level.
4. Always use query_params for user-supplied values - never template- literal-interpolate them into SQL. See reference/query-parameters.md. When answering a parameter-binding question, your response must explicitly name template-literal interpolation as a "SQL injection risk" - even when the user only asked about syntax and did not raise security. The literal phrase "SQL injection" needs to appear; this is the most common mistake from PostgreSQL/MySQL users and the security framing is part of the correct answer, not an optional aside.
5. Pick the right method for the job:
   • client.insert() - write rows.
   • client.query() + resultSet.json() / .text() / .stream() - read rows that return data.
   • client.command() - DDL and other statements that don't return rows (CREATE, DROP, TRUNCATE, ALTER, SET in a session, etc.).
   • client.exec() - when you need the raw response stream of an arbitrary statement (rare in coding scenarios).
   • client.ping() - health check; returns { success, error? }, never throws on connection failure.
6. Note version constraints when relevant. Examples:
   • pathname config option: client >= 1.0.0.
   • BigInt values in query_params: client >= 1.15.0.
   • TupleParam and JS Map in query_params: client >= 1.9.0.
   • Configurable json.parse / json.stringify: client >= 1.14.0.
   • Time / Time64 data types: ClickHouse server >= 25.6.
   • Dynamic / Variant / new JSON types: ClickHouse server >= 24.1 / 24.5 / 24.8 (no longer experimental since 25.3).

---

Task Index

Identify the user's task and read the matching reference file.

Task	Triggers / symptoms	Reference file
Configure / connect the client	Building a createClient call, URL parameters, clickhouse_settings, default format, custom HTTP headers	reference/client-configuration.md
Ping the server	Health checks, readiness probes, "is ClickHouse up?"	reference/ping.md
Choose an insert format	"Which format should I use to insert?", JSON vs raw, JSONEachRow vs JSON vs JSONObjectEachRow	reference/insert-formats.md
Insert into a subset of columns / different database	insert({ columns }), excluding columns, ephemeral columns, cross-DB inserts	reference/insert-columns.md
Insert values, expressions, dates, decimals	INSERT ... VALUES with SQL functions, Date/DateTime from JS, Decimal precision, INSERT ... SELECT	reference/insert-values.md
Async inserts (server-side batching)	async_insert=1, fire-and-forget vs wait-for-ack	reference/async-insert.md
Select and parse results	JSONEachRow reads, JSON with metadata, picking a select format	reference/select-formats.md
Parameterize queries	Binding values, special characters / escaping, "SQL injection?", {name: Type} syntax	reference/query-parameters.md
Sessions & temporary tables	session_id, CREATE TEMPORARY TABLE, per-session SET commands	reference/sessions.md
Modern data types	Dynamic, Variant, JSON (object), Time, Time64	reference/data-types.md
Custom JSON parse/stringify	Plug in JSONBig / safe-stable-stringify / a BigInt-aware serializer	reference/custom-json.md

---

Conventions used in answers

• Always show import { createClient } from '@clickhouse/client' (Node, never Web).
• Always await client.close() at the end of self-contained snippets; in long-running services, close on graceful shutdown.
• For inserts, prefer format: 'JSONEachRow' and values: [...] unless the user's scenario requires otherwise.
• For selects, prefer await (await client.query({...})).json<RowType>() for small / medium result sets; for bigger results suggest streaming.
• When showing parameter binding, use ClickHouse's native {name: Type} syntax - never $1, ?, or :name.
• For DDL inside a cluster or behind a load balancer, set clickhouse_settings: { wait_end_of_query: 1 } on the command() call so the server only acknowledges after the change is applied. See https://clickhouse.com/docs/en/interfaces/http/#response-buffering.

---

Out of scope

This skill covers day-to-day coding against @clickhouse/client (Node). The following topics are intentionally not covered here:

• Errors, hangs, type mismatches, proxy pathname surprises, log silence, socket hang-ups, ECONNRESET -> use the clickhouse-js-node-troubleshooting skill.
• Streaming, Parquet, file streams, server-side bulk moves, progress streaming, async-insert throughput tuning - see examples/node/performance/.
• TLS, RBAC / read-only users, deeper SQL-injection guidance - see examples/node/security/.
• CREATE TABLE patterns, deployment-shaped connection strings, replication / sharding choices - see examples/node/schema-and-deployments/.
• Browser, Web Worker, Next.js Edge, Cloudflare Workers - use @clickhouse/client-web and see examples/web/.

---

Still Stuck?

• examples/node/coding/ - the runnable corpus this skill is built on.
• ClickHouse JS client docs
• ClickHouse supported formats
• ClickHouse data types