SQLITE_WARNINGWARNINGTier 1 — Safe⚠️ MEDIUM confidence

Warning from sqlite3_log()

Category: LoggingVersions: 3.7.15+

🔴 Production Risk Error

Low — warnings indicate potential performance issues, not failures.

What this means

SQLITE_WARNING (28) is passed to the sqlite3_log() callback for warnings — non-fatal issues that may indicate a misconfiguration or suboptimal usage, such as using an auto-index.

Why it happens

1SQLite created an automatic index to satisfy a query (SQLITE_WARNING_AUTOINDEX).
2Extension or VFS emitting a non-fatal warning.

How to reproduce

sqlite3_log() callback; not returned by API functions.

trigger — this will ERROR

-- Trigger SQLITE_WARNING_AUTOINDEX:
PRAGMA automatic_index = ON;
CREATE TABLE a(x); CREATE TABLE b(x);
-- Unindexed join forces autoindex:
SELECT * FROM a JOIN b ON a.x = b.x;
-- Log will show: "automatic index on b(x)"

Log message: "automatic index on b(x)" with code SQLITE_WARNING_AUTOINDEX (284).

Fix 1

Why this works

Add a manual index on the joined column to suppress the autoindex warning: CREATE INDEX idx_b_x ON b(x);

Version notes

Dangerous variant

⚠️ Warning

SQLITE_WARNING_AUTOINDEX (284) — query using an automatic index; may be slow.

Sources

📚 Official docs: https://www.sqlite.org/rescode.html#warning

🔧 Source ref: sqlite3.h — SQLITE_WARNING = 28

📖 Further reading: Automatic indexes in SQLite

Confidence assessment

⚠️ MEDIUM confidence

Stable.