#Values and errors

Value is the parameter boundary between compiler and executor and the common representation for driver rows before decoding.

#Value variants

SqlArray<T> separates SQL arrays from Vec<u8> byte semantics. PostgreSQL converts each item against the server-inferred element type and reports its index on failure.

#Build errors

Top-level Error covers invalid identifiers, empty projections, invalid scalar subqueries, duplicate CTEs, invalid window frames, empty writes, column ownership, conflict structure, lock targets, and dialect compilation.

A build error means the query never reached an executor. Fix query structure instead of retrying it as a transient database failure.

#Decode errors

DecodeError distinguishes:

• Missing expected column index.
• Actual Value type incompatible with the target Rust type.
• Integer outside the target range.
• SQL array element that could not decode.

Option<T> maps only Value::Null to None. It does not hide other type errors.

#Driver errors

SQLite errors retain execution, parameter, and transaction stages. A scoped transaction can preserve both operation and rollback errors without discarding the primary failure.

PostgreSQL errors also provide retry_class() and is_retryable(). Classification is stable policy input, not automatic retry behavior. See PostgreSQL and high availability.

#Logging errors

• Do not log credential-bearing connection URLs.
• TLS option Debug omits PEM, but applications must still protect original secret buffers.
• Pool metrics omit high-cardinality labels. Never turn SQL or complete error messages into metric labels.
• Log the DatabaseError stage and bounded business context while retaining the error source chain.