windmill-labs/windmill · warning

SQL_PREPARATION_ERROR

SQL_PREPARATION_ERROR

Error message

Failed to prepare query: db error: ERROR: <db error text> (prefix stripped; messageText is the prepared-query error, surfaced as a Monaco diagnostic)

What it means

In the SQL language worker for Monaco (frontend/src/lib/monaco_workers/sqlTypePlugin.worker.js), _createSqlErrorDiagnostics converts a database-side prepared-query failure into an editor diagnostic. The raw backend message has the shape 'Failed to prepare query: db error: ERROR: <db error text>'; the worker strips that prefix and surfaces only the underlying DB messageText as a red squiggle under the offending template-literal query, tagged with code SQL_PREPARATION_ERROR.

Source

Thrown at frontend/src/lib/monaco_workers/sqlTypePlugin.worker.js:700

		const originalCode = cached?.originalText ?? ''
		if (!originalCode) {
			// Fallback if no cached result
			const originalSnapshot = super.getScriptSnapshot(fileName)
			if (!originalSnapshot) {
				return []
			}
		}

		const sqlDiagnostics = []
		for (const query of queries) {
			let messageText = query?.prepared?.error
			if (typeof messageText === 'string') {
				let queryStartIdx = originalCode.indexOf('`', (query.span?.[0] || 1) - 1) + 1
				// Create a diagnostic error for this query
				let prefix = 'Failed to prepare query: db error: ERROR: '
				if (messageText.startsWith(prefix)) messageText = messageText.substring(prefix.length)
				const diagnostic = {
					code: 'SQL_PREPARATION_ERROR',
					category: ts.typescript.DiagnosticCategory.Error,
					messageText,
					file: fileName,
					start: queryStartIdx,
					length: query.span?.[1] ? query.span[1] - queryStartIdx - 2 : 0,
					source: 'sql'
				}
				sqlDiagnostics.push(diagnostic)
			}
		}

		return sqlDiagnostics
	}

	async getSyntacticDiagnostics(fileName) {
		const diagnostics = await super.getSyntacticDiagnostics(fileName)
		return this._mapDiagnostics(diagnostics, fileName)
	}

View on GitHub (pinned to e474e8803c)

Solutions

1. Read the diagnostic message — after prefix stripping it is the raw DB error (e.g. 'column "foo" does not exist'); fix the SQL accordingly.
2. Hover over the squiggle: start/length map to the failing backtick query span in the editor.
3. Verify the connection's target database/dialect actually supports the SQL you wrote.
4. Check that placeholder count ($1…) matches your args if using parameterized queries.
5. If the diagnostic looks stale, retrigger analysis by editing the query — the worker only reports errors from the last prepare round.

Example fix

// before
const q = `SELECT usernmae FROM users WHERE id = $1`
// after (fixing the unknown column reported by the diagnostic)
const q = `SELECT username FROM users WHERE id = $1`

function isSqlPreparationDiagnostic(d: ts.typescript.Diagnostic): boolean {
  return (d as { code?: number | string }).code === 'SQL_PREPARATION_ERROR' || d.source === 'sql'
}

// Monaco language-service context: consume diagnostics, don't catch
monaco.editor.onDidChangeMarkers => {
  const diags = monaco.editor.getModelMarkers({ owner: 'sql' })
  for (const d of diags.filter(isSqlPreparationDiagnostic)) {
    console.log(`SQL error at ${d.startLineNumber}: ${d.message}`)
  }
}

When it happens

Trigger: Editing a script/app that contains a backtick-quoted SQL query; the language service sends the query to the database to prepare it; the DB rejects it (syntax error, unknown table/column, wrong placeholder count, permission denied) and the worker builds a diagnostic from the returned messageText.

Common situations: Typo in SQL syntax; referencing a table or column that does not exist in the connected database; using $1/$2 placeholders inconsistent with provided args; dialect mismatch (Postgres-only syntax on MySQL connection); the preview database being unreachable or the user lacking permissions.

Related errors

• Invalid group
• [SqlTypeService] Worker initialization timeout for ${uri.toS
• [SqlTypeService] Worker initialization failed for ${uri.toSt
• Error executing query: {:?}
• result.substring(__RESULT_ERR_PREFIX.length)

AI-assisted analysis of windmill-labs/windmill@e474e8803c (2026-09-03). Data as JSON: /api/errors/cdfc90b9af39852a. Report an issue: GitHub.