ClickHouse

Column-oriented analytical database over HTTP.

At a glance

• Category — Relational
• Query language — SQL
• Default port — 8123
• URI scheme — http

Connecting

The driver speaks ClickHouse’s HTTP interface rather than the native protocol, so the endpoint is a URL and not a host/port pair.

Field	Default	Notes
HTTP URL	http://localhost:8123	https:// endpoints are served over rustls
Database	default	Scopes schema discovery and unqualified queries
Request timeout	30 seconds	Must be greater than zero
User	default
Password	—	Held in the OS keyring and sent as HTTP Basic auth

Features

• Blocking HTTP(S) transport built on rustls, authenticating with HTTP Basic.
• Arbitrary single-statement SQL, with responses forced to JSONCompact so column names and types arrive alongside the rows.
• Row width is checked against the declared column count on every response, so a malformed reply fails with a clear error instead of shifting values between columns.
• Schema discovery from system.databases, system.tables and system.columns: databases, tables, views, columns, engine, sorting and partition keys, on-disk size, and compression.
• Schema loading is lazy per database, so a server with many databases does not pay for all of them at connect time.
• Pagination, sorting and filtering are applied by the driver as LIMIT/OFFSET around the statement, which is what makes result browsing work without a cursor.
• Read-only visual SELECT generation, using ClickHouse identifier and literal quoting rules.
• Chart authoring from query results, and CSV and JSON export.

Type handling

Values are decoded recursively, so a Map(String, Array(Nullable(Decimal256))) arrives fully structured rather than as raw text:

• Wrappers — Nullable, LowCardinality
• Containers — Array, Tuple, Map, Nested
• Numbers — integers up to UInt256, Decimal256, BFloat16, Bool
• Time — Date32, DateTime64
• Other — Enum16, Nothing

Limitations

• No SSH tunnels.
• No transactions, prepared statements, or query cancellation. A running statement is bounded by the request timeout and nothing else, and the driver reports no lock-timeout support.
• No structured INSERT, UPDATE, DELETE, DDL, or data-transfer support. Write SQL runs only when typed explicitly into the editor, so the grid is read-only and the driver is not a transfer target.
• One SQL statement per request; multi-statement scripts are not batched.
• HTTP response bodies are capped at 128 MiB.
• Named ClickHouse time zones are not interpreted client-side. ISO timestamps carrying an offset are handled accurately; timestamps without one are treated as UTC.