DuckDB contains a logging mechanism to provide additional information to users, such as query execution details, performance metrics, and system events.

Basics

DuckDB's logging mechanism can be enabled or disabled using pragmas. By default, logs are stored in a special table called duckdb_logs that can be queried like any other table.

Example:

PRAGMA enable_logging;
-- Run some queries..
SELECT * FROM duckdb_logs;

Log Level

DuckDB supports different logging levels that control the verbosity of the logs:

• ERROR: Only logs error messages
• WARN: Logs warnings and errors
• INFO: Logs general information, warnings and errors (default)
• DEBUG: Logs detailed debugging information
• TRACE: Logs very detailed tracing information

The log level can be set using:

PRAGMA enable_logging;
SET logging_level = 'TRACE';

Log Types

In DuckDB, log messages can have an associated log type. Log types have 2 main goals. Firstly, they allow using includelists and excludelist to limit which types of log messages are logged. Secondly, log types can have a predetermined message schema which allows DuckDB to automatically parse the messages back into a structured data type.

Logging-Specific Types

To log only messages of a specific type:

PRAGMA enable_logging('HTTP');

The above pragma will automatically set the correct log level, and will add the HTTP type to the enabled_log_types settings.

Structured Logging

Some log types like HTTP will have an associated message schema. To make DuckDB automatically parse the message, use the duckdb_logs_parsed() macro. For example:

SELECT request.headers FROM duckdb_logs_parsed('HTTP');

List of Available Log Types

This is a (non-exhaustive) list of the available log types in DuckDB.

Log Storage

By default, DuckDB logs to an in-memory log storage. Alternatively, DuckDB can log straight to stdout using:

PRAGMA enable_logging;
SET logging_storage = 'stdout';