prestodb/presto · warning · SQLException

Max field size must be positive

Error message

Max field size must be positive

What it means

JDBC's setMaxFieldSize limits the maximum bytes returned per field. Presto's driver always returns full values (the limit is ignored), but still validates the argument: a negative max is rejected with this SQLException before the no-op comment.

Source

Thrown at presto-jdbc/src/main/java/com/facebook/presto/jdbc/PrestoStatement.java:107

        connection.set(null);
        closeResultSet();
    }

    @Override
    public int getMaxFieldSize()
            throws SQLException
    {
        checkOpen();
        return 0;
    }

    @Override
    public void setMaxFieldSize(int max)
            throws SQLException
    {
        checkOpen();
        if (max < 0) {
            throw new SQLException("Max field size must be positive");
        }
        // ignore: full values are always returned
    }

    @Override
    public int getMaxRows()
            throws SQLException
    {
        long result = getLargeMaxRows();
        if (result > Integer.MAX_VALUE) {
            throw new SQLException("Max rows exceeds limit of 2147483647");
        }
        return toIntExact(result);
    }

    @Override
    public long getLargeMaxRows()
            throws SQLException

View on GitHub (pinned to 55bb57d202)

Solutions

1. Pass 0 (or a positive value) — in JDBC, 0 means no limit
2. Fix sentinel logic that uses -1 for unlimited
3. Check the value computed before passing it to setMaxFieldSize

Example fix

// before
stmt.setMaxFieldSize(-1); // unlimited?
// after
stmt.setMaxFieldSize(0); // 0 = no limit

if (maxFieldSize < 0) {
    throw new IllegalArgumentException("maxFieldSize must be >= 0 (0 = no limit), got " + maxFieldSize);
}
stmt.setMaxFieldSize(maxFieldSize);

try {
    stmt.setMaxFieldSize(n);
} catch (SQLException e) {
    if (e.getMessage() != null && e.getMessage().contains("Max field size must be positive")) {
        stmt.setMaxFieldSize(0); // fall back to unlimited
    } else { throw e; }
}

When it happens

Trigger: Calling PrestoStatement.setMaxFieldSize with a negative integer, e.g. -1 used as a sentinel for 'unlimited'.

Common situations: Using -1 as an 'unbounded' sentinel (in this driver 0 is the correct unlimited value); uninitialized/default-negative int variables; porting code from drivers that tolerated negatives.

Related errors

• Max rows must be positive
• Timeout is negative
• Query has no columns (#%s)
• SQL statement is not a query:
• Max rows exceeds limit of 2147483647

AI-assisted analysis of prestodb/presto@55bb57d202 (2026-09-04). Data as JSON: /api/errors/43bb03daced78068. Report an issue: GitHub.