Skip to main content
Community Hub

Query redaction for Tableau

TL;DR

Reference for Redact SQL Text on the Tableau crawler workflow: what Atlan redacts, what it preserves, and limitations to plan for.

Your AI can read this via Docs MCPcurl -fsSL "https://docs.atlan.com/install-docs-mcp" | bashConnect

By default, Atlan stores the custom SQL it extracts from Tableau exactly as written in Tableau. That text can contain literal values from your business data, such as email addresses in a WHERE clause or account numbers in a filter.

Query redaction replaces those literal values with placeholders before Atlan stores them. Redaction runs in memory while the workflow extracts data, so the original values aren't written to Atlan's storage or sent outside your environment. Query structure, table references, and column references are preserved, so lineage is unaffected.

Redaction is off by default. You opt in using the Redact SQL Text option on the crawler.

Enable redaction​

WorkflowWhere to find it
Tableau crawlerAdvanced page

The option appears for both direct and Self-Deployed Runtime extraction. With Self-Deployed Runtime extraction, redaction runs inside your Self-Deployed Runtime.

What Atlan redacts​

Redaction applies to the fields that carry SQL text.

SourceRedacted content
Tableau Metadata APIThe query of each custom SQL table
Downloaded workbook and data source definitionsCustom SQL relations and Initial SQL. Applies only when Download Workbook and Data Source Definitions is also enabled.

Within the redacted text, Atlan replaces:

  • String literals with '<REDACTED:STRING>'.
  • Numeric literals with 1. Atlan substitutes a valid number rather than a text placeholder so that the redacted SQL remains parseable.

Atlan also removes comments from redacted SQL and reformats the statement, so stored text won't match the original layout.

Values Atlan preserves​

Some literals are safe to keep and can break the SQL if replaced, so redaction preserves them:

  • Date and time literals, such as '2026-01-01' or '2026-01-01 14:30:00'.
  • Month and weekday names, and date part keywords such as MONTH or QUARTER.
  • Currency codes, such as 'USD'.
  • Boolean words: TRUE, FALSE, YES, and NO.
  • Numbers in structural positions, such as the row count in a LIMIT clause, where the value controls the shape of the result rather than describing your data.

Everything else is treated as potentially sensitive and redacted.

Before and after​

A custom SQL query on a Google BigQuery connection:

-- monthly EMEA revenue check
select order_id, customer_email
from `my-project.analytics.orders`
where region = 'EMEA' and order_total > 500.75
  and created_at >= '2026-01-01' and currency = 'USD'
limit 100;

The same query as Atlan stores it with Redact SQL Text enabled:

/* redacted: true, hash: <original_hash>, redacted_hash: <redacted_hash> */
SELECT
  order_id,
  customer_email
FROM `my-project.analytics.orders`
WHERE
  region = '<REDACTED:STRING>'
  AND order_total > 1
  AND created_at >= '2026-01-01'
  AND currency = 'USD'
LIMIT 100

Note the following:

  • 'EMEA' was replaced, while the date and the currency code were preserved.
  • 500.75 became 1. Redaction indicates that a number was present, not what it was.
  • LIMIT 100 was preserved, because the number controls the result size rather than describing your data.
  • The comment was removed and the statement was reformatted.
  • Atlan adds a header comment recording that the text was redacted, along with fingerprints of the original and redacted statements. The fingerprint values differ for every statement.
  • my-project.analytics.orders, order_id, and customer_email are unchanged, which is why lineage still resolves.

What redaction preserves​

Redaction only changes literal values. Because everything Atlan uses to build relationships stays intact, enabling redaction doesn't change:

  • Lineage from custom SQL to upstream tables and columns.
  • Asset names, hierarchy, or any other extracted metadata.

Limitations​

SQL that Atlan can't parse is stored unredacted. When parsing fails, Atlan stores the original query under a redacted: false header instead of dropping it. A downloaded definition that Atlan can't redact is stored as downloaded.

Redaction increases workflow runtime. Expect crawler runs to take longer, and account for this if the crawler already runs close to its schedule interval.

Enabling redaction rewrites stored SQL. Because the stored text changes for every custom SQL table, the first run after you enable the option updates SQL text across the connection.

See also​