Logging

It is possible to set up logs for all queries using the log property when instantiating Kysely.

There are 2 ways to configure logging:

1. Provide an array with log level/s

You can provide an array of log levels to the log property when instantiating Kysely.

When 'query' is included in the array, Kysely will log all executed queries, not including parameter values.

When 'error' is included in the array, Kysely will log all errors.

const db = new Kysely({
  ...
  log: ['query', 'error']
  ...
});

2. Provide a custom logging function

You can provide a custom logging function to the log property when instantiating Kysely. The custom logging function receives a log event as an argument.

LogEvent is a discriminated union. Query events may have isStream; only error events have an error property:

type LogEvent =
  | {
      level: 'query'
      isStream?: boolean
      query: CompiledQuery
      queryDurationMillis: number
    }
  | {
      level: 'error'
      error: unknown
      query: CompiledQuery
      queryDurationMillis: number
    }

Example:

const db = new Kysely({
  dialect: new PostgresDialect(postgresConfig),
  log(event) {
    if (event.level === "error") {
        console.error("Query failed : ", {
          durationMs: event.queryDurationMillis,
          error: event.error,
          sql: event.query.sql,
          params: event.query.parameters.map(maskPII),
        });
    } else { // `'query'`
      console.log("Query executed : ", {
        durationMs: event.queryDurationMillis,
        sql: event.query.sql,
        params: event.query.parameters.map(maskPII),
      });
    }
  }
})

For more information check the docs for details on the interfaces KyselyConfig.