ClickHouse

Pro

DevDb connects to ClickHouse over its HTTP interface. It works with local servers and with ClickHouse Cloud.

Connect

From the panel

1. Under Remote Connections, click Add, then select ClickHouse.
2. Enter the details:

Field	Default	Description
Host	localhost	Server host
Port	8123	HTTP port. ClickHouse Cloud uses 8443.
Protocol	See HTTP or HTTPS	HTTPS (ClickHouse Cloud, port 8443) or HTTP (local, port 8123)
Username	default	User
Password	—	Password
Database	default	Database to open

3. Click Test, then click Connect.

DevDb checks the password when it connects. A wrong password gives an error immediately.

From .devdbrc

[
  {
    "name": "Local ClickHouse",
    "type": "clickhouse",
    "host": "localhost",
    "port": 8123,
    "protocol": "http"
  }
]

See the ClickHouse reference for all keys.

HTTP or HTTPS

If you do not select a protocol, DevDb selects one:

Host and port	Protocol
Port 8443 or 9440	https
Any host that is not local	https
localhost, 127.0.0.1 or ::1	http

If you select http for a host that is not local, DevDb connects, but it writes a warning to the DevDb output channel. Over http, your password and data are not encrypted. Use https for remote servers.

Query stats

After each query, DevDb shows the statistics that the server sends, below the results. For example:

scanned 1,234,567 rows · 45.6 MB · 0.08s

• scanned ... rows: rows that ClickHouse read.
• MB: bytes that ClickHouse read.
• s: time on the server.

Cancel a query

While a query runs, DevDb shows a bar with a Cancel button. When you click it, DevDb closes the request and sends KILL QUERY for that query. The query stops on the server, not only in DevDb.

Limits

DevDb sets limits on each query so that one query cannot overload the server or your editor:

Limit	Table browsing	Raw queries (for example from MCP)
Time	60 seconds	30 seconds
Server memory	2 GiB	2 GiB
Rows returned	One page	10,000 rows
Result size	One page	64 MiB

When a raw query reaches a row or size limit, DevDb shows the partial result.

Data types

• Decimal values keep their full precision.
• Nullable(...) and LowCardinality(...) columns show their base type.
• Array, Tuple, Map and Nested values show as JSON.

Edit data

You can edit values, set values to null and delete rows. ClickHouse applies these changes as mutations (ALTER TABLE ... UPDATE and ALTER TABLE ... DELETE). DevDb waits until the mutation is complete (mutations_sync = 1). On large tables, a save can take some time.