Skip to main content
Version: Next (unreleased)

Redaction & Fingerprints

sqlguard's findings flow into logs. A query like SELECT * FROM users WHERE email = 'ceo@example.com' is exactly the query most likely to trip a rule, and the literal in it is exactly what must not reach a log sink. So by default no Result leaves the process with a literal value in it. This is a security invariant, not a formatting choice — see the repository's SECURITY.md.

What redaction does​

analyzer.Redact is a zero-dependency lexical pass over the SQL:

  • Comments (-- and /* */) are stripped.
  • Every single-quoted string literal becomes ?, honoring '' escapes.
  • Every numeric literal becomes ?.
  • Keywords, structure, and identifiers — including "double-quoted" and `backtick` names — are preserved.

It never errors; unparseable input still comes out with its literals gone.

in:  SELECT * FROM "users" WHERE email = 'a@b.c' AND age > 30 -- vip
out: SELECT * FROM "users" WHERE email = ? AND age > ?

Result.Query is set from Redact centrally in Analyzer.Analyze, and the findings built outside the rule path — slow-query and n-plus-one — go through Analyzer.PrepareQuery, which applies the same policy. There is one normalizer in the codebase; nothing re-implements it.

Fingerprints​

Every Result also carries Fingerprint: the redacted query with whitespace collapsed, IN (?, ?, ?) and VALUES (?, ?) lists folded to (?), and a trailing ; trimmed.

SELECT id FROM t WHERE x IN (1, 2, 3)   →  SELECT id FROM t WHERE x IN (?)
SELECT id FROM t WHERE x IN (4, 5)      →  SELECT id FROM t WHERE x IN (?)
SELECT id\n  FROM t\n  WHERE x = 'a';   →  SELECT id FROM t WHERE x = ?

A fingerprint is:

  • Stable — the same query shape always yields the same string.
  • PII-free — it is derived from the redacted form.
  • Low-cardinality — literals and list lengths do not create new values.

That makes it safe as a metrics label, a log key, or a grouping key in your observability stack. It is the value the N+1 tracker groups on and the de-duplicator keys on. The JSON reporter emits it as fingerprint; analyzer.Fingerprint(sql) computes it directly.

Fingerprint is always populated, whether or not redaction is on.

Opting out​

Only where the query text is trusted — local debugging, a test — you can keep the raw SQL in Result.Query:

a := analyzer.Default().WithRawQuery()
sqlguard.Register("sqlguard-pg", "pgx", middleware.WithAnalyzer(a))

or in .sqlguard.yml:

redact: false

WithRawQuery returns a copy; the original analyzer is unchanged. Do not ship this to production.

The one deliberate exception​

The EXPLAIN analyzer keeps Result.Query raw. The user typed the query on their own command line; it goes back to their own terminal and never reaches a log or telemetry sink. Fingerprint is still set. The exception is scoped to explain only.

Using it in your own reporter​

type metricsReporter struct{ counter *prometheus.CounterVec }

func (m *metricsReporter) Report(rs []analyzer.Result) {
    for _, r := range rs {
        m.counter.WithLabelValues(r.RuleName, r.Fingerprint).Inc()
    }
}

RuleName and Fingerprint are the two fields designed to be labels. Query is for humans and Message for context; neither should be a metric dimension.