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rudb_common/
value.rs

1//! Single values.
2//!
3//! A `Value` is one SQL value, boxed up on its own. It is what a literal parses into, what a
4//! constant folds to, and what a result set is read out as one cell at a time. It is deliberately
5//! not what execution runs on: `spec/07-execution.md` says the unit of data is a vector of 1024,
6//! and an operator that touches a `Value` per row is an operator that has already lost.
7//!
8//! The formatting here is DuckDB's, because a shell that prints `2024-01-15` where DuckDB prints
9//! `2024-01-15` is a shell whose output can be diffed against DuckDB's in `tamnd/rudb-compat`.
10
11use std::fmt;
12
13use crate::types::LogicalType;
14
15/// A single SQL value.
16///
17/// `PartialEq` here is Rust equality and not SQL equality. Two nulls compare equal and two NaNs
18/// compare equal, both of which SQL disagrees with. That is the right behaviour for a test
19/// assertion and the wrong behaviour for a `WHERE` clause, and the `WHERE` clause gets its
20/// comparison from the kernels rather than from here.
21#[derive(Debug, Clone, PartialEq)]
22#[non_exhaustive]
23pub enum Value {
24    /// `NULL`, of no particular type.
25    Null,
26    /// `BOOLEAN`.
27    Boolean(bool),
28    /// `TINYINT`.
29    TinyInt(i8),
30    /// `SMALLINT`.
31    SmallInt(i16),
32    /// `INTEGER`.
33    Integer(i32),
34    /// `BIGINT`.
35    BigInt(i64),
36    /// `HUGEINT`.
37    HugeInt(i128),
38    /// `UTINYINT`.
39    UTinyInt(u8),
40    /// `USMALLINT`.
41    USmallInt(u16),
42    /// `UINTEGER`.
43    UInteger(u32),
44    /// `UBIGINT`.
45    UBigInt(u64),
46    /// `UHUGEINT`.
47    UHugeInt(u128),
48    /// `FLOAT`.
49    Float(f32),
50    /// `DOUBLE`.
51    Double(f64),
52    /// `DECIMAL(width, scale)`, carrying the unscaled integer.
53    Decimal {
54        /// The unscaled value, so 12.34 at scale 2 is 1234.
55        unscaled: i128,
56        /// Total digits.
57        width: u8,
58        /// Digits right of the point.
59        scale: u8,
60    },
61    /// `VARCHAR`.
62    Varchar(String),
63    /// `BLOB`.
64    Blob(Vec<u8>),
65    /// `DATE`, days since 1970-01-01.
66    Date(i32),
67    /// `TIME`, microseconds since midnight.
68    Time(i64),
69    /// `TIMESTAMP`, microseconds since 1970-01-01 00:00:00.
70    Timestamp(i64),
71    /// `INTERVAL`, the months, days and microseconds triple.
72    ///
73    /// Three fields rather than one duration because interval arithmetic with months is not
74    /// associative with days, and DuckDB's specific behaviour is what tests assert on. A month is
75    /// not 30 days and this representation is what refuses to pretend otherwise.
76    Interval {
77        /// Whole months.
78        months: i32,
79        /// Whole days.
80        days: i32,
81        /// Microseconds.
82        micros: i64,
83    },
84    /// A list, carrying its element type so that an empty list still knows what it is empty of.
85    List {
86        /// The element type.
87        element: LogicalType,
88        /// The elements.
89        values: Vec<Value>,
90    },
91    /// A struct, in field order.
92    Struct(Vec<(String, Value)>),
93}
94
95impl Value {
96    /// Whether this is `NULL`.
97    #[must_use]
98    pub fn is_null(&self) -> bool {
99        matches!(self, Self::Null)
100    }
101
102    /// The type of this value.
103    #[must_use]
104    pub fn logical_type(&self) -> LogicalType {
105        match self {
106            Self::Null => LogicalType::Null,
107            Self::Boolean(_) => LogicalType::Boolean,
108            Self::TinyInt(_) => LogicalType::TinyInt,
109            Self::SmallInt(_) => LogicalType::SmallInt,
110            Self::Integer(_) => LogicalType::Integer,
111            Self::BigInt(_) => LogicalType::BigInt,
112            Self::HugeInt(_) => LogicalType::HugeInt,
113            Self::UTinyInt(_) => LogicalType::UTinyInt,
114            Self::USmallInt(_) => LogicalType::USmallInt,
115            Self::UInteger(_) => LogicalType::UInteger,
116            Self::UBigInt(_) => LogicalType::UBigInt,
117            Self::UHugeInt(_) => LogicalType::UHugeInt,
118            Self::Float(_) => LogicalType::Float,
119            Self::Double(_) => LogicalType::Double,
120            Self::Decimal { width, scale, .. } => {
121                LogicalType::Decimal { width: *width, scale: *scale }
122            }
123            Self::Varchar(_) => LogicalType::Varchar,
124            Self::Blob(_) => LogicalType::Blob,
125            Self::Date(_) => LogicalType::Date,
126            Self::Time(_) => LogicalType::Time,
127            Self::Timestamp(_) => LogicalType::Timestamp,
128            Self::Interval { .. } => LogicalType::Interval,
129            Self::List { element, .. } => LogicalType::list(element.clone()),
130            Self::Struct(fields) => LogicalType::Struct(
131                fields
132                    .iter()
133                    .map(|(name, value)| crate::types::Field::new(name, value.logical_type()))
134                    .collect(),
135            ),
136        }
137    }
138
139    /// The value as an `i64`, for the integer types that fit in one.
140    ///
141    /// Used by the planner for the places where a literal has to be a small integer, `LIMIT` and
142    /// `OFFSET` being the obvious ones. Returns `None` rather than saturating, because a `LIMIT`
143    /// that silently became `i64::MAX` is worse than an error.
144    #[must_use]
145    pub fn as_i64(&self) -> Option<i64> {
146        match *self {
147            Self::TinyInt(v) => Some(i64::from(v)),
148            Self::SmallInt(v) => Some(i64::from(v)),
149            Self::Integer(v) => Some(i64::from(v)),
150            Self::BigInt(v) => Some(v),
151            Self::UTinyInt(v) => Some(i64::from(v)),
152            Self::USmallInt(v) => Some(i64::from(v)),
153            Self::UInteger(v) => Some(i64::from(v)),
154            Self::UBigInt(v) => i64::try_from(v).ok(),
155            Self::HugeInt(v) => i64::try_from(v).ok(),
156            Self::UHugeInt(v) => i64::try_from(v).ok(),
157            _ => None,
158        }
159    }
160
161    /// The value as a `bool`, for a `BOOLEAN` and nothing else.
162    #[must_use]
163    pub fn as_bool(&self) -> Option<bool> {
164        match *self {
165            Self::Boolean(v) => Some(v),
166            _ => None,
167        }
168    }
169
170    /// The value as a string slice, for a `VARCHAR` and nothing else.
171    #[must_use]
172    pub fn as_str(&self) -> Option<&str> {
173        match self {
174            Self::Varchar(v) => Some(v),
175            _ => None,
176        }
177    }
178}
179
180impl fmt::Display for Value {
181    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
182        match self {
183            Self::Null => f.write_str("NULL"),
184            Self::Boolean(v) => f.write_str(if *v { "true" } else { "false" }),
185            Self::TinyInt(v) => write!(f, "{v}"),
186            Self::SmallInt(v) => write!(f, "{v}"),
187            Self::Integer(v) => write!(f, "{v}"),
188            Self::BigInt(v) => write!(f, "{v}"),
189            Self::HugeInt(v) => write!(f, "{v}"),
190            Self::UTinyInt(v) => write!(f, "{v}"),
191            Self::USmallInt(v) => write!(f, "{v}"),
192            Self::UInteger(v) => write!(f, "{v}"),
193            Self::UBigInt(v) => write!(f, "{v}"),
194            Self::UHugeInt(v) => write!(f, "{v}"),
195            Self::Float(v) => write_float(f, *v),
196            Self::Double(v) => write_float(f, *v),
197            Self::Decimal { unscaled, scale, .. } => write_decimal(f, *unscaled, *scale),
198            Self::Varchar(v) => f.write_str(v),
199            Self::Blob(v) => write_blob(f, v),
200            Self::Date(v) => write_date(f, *v),
201            Self::Time(v) => write_time(f, *v),
202            Self::Timestamp(v) => write_timestamp(f, *v),
203            Self::Interval { months, days, micros } => write_interval(f, *months, *days, *micros),
204            Self::List { values, .. } => {
205                f.write_str("[")?;
206                for (index, value) in values.iter().enumerate() {
207                    if index > 0 {
208                        f.write_str(", ")?;
209                    }
210                    write!(f, "{value}")?;
211                }
212                f.write_str("]")
213            }
214            Self::Struct(fields) => {
215                f.write_str("{")?;
216                for (index, (name, value)) in fields.iter().enumerate() {
217                    if index > 0 {
218                        f.write_str(", ")?;
219                    }
220                    write!(f, "'{name}': {value}")?;
221                }
222                f.write_str("}")
223            }
224        }
225    }
226}
227
228/// The two float types, so that one printer can serve both without going through `f64`.
229///
230/// Widening an `f32` to print it is wrong and quietly so: `0.1f32` as an `f64` is
231/// `0.10000000149011612`, and the shortest text that reads back as the same `f32` is `0.1`. DuckDB
232/// prints `0.1`, and it prints it because it formats the `float` rather than a `double` made out of
233/// one.
234trait Real: Copy + fmt::Display + fmt::LowerExp {
235    fn is_nan(self) -> bool;
236    fn is_infinite(self) -> bool;
237    fn is_sign_negative(self) -> bool;
238}
239
240impl Real for f32 {
241    fn is_nan(self) -> bool {
242        Self::is_nan(self)
243    }
244
245    fn is_infinite(self) -> bool {
246        Self::is_infinite(self)
247    }
248
249    fn is_sign_negative(self) -> bool {
250        Self::is_sign_negative(self)
251    }
252}
253
254impl Real for f64 {
255    fn is_nan(self) -> bool {
256        Self::is_nan(self)
257    }
258
259    fn is_infinite(self) -> bool {
260        Self::is_infinite(self)
261    }
262
263    fn is_sign_negative(self) -> bool {
264        Self::is_sign_negative(self)
265    }
266}
267
268/// Floats print the shortest text that reads back as the same value, laid out the way DuckDB lays
269/// it out.
270///
271/// Rust and DuckDB agree on the digits and disagree on everything around them. A float with nothing
272/// after the point keeps its `.0`, so a `DOUBLE` never looks like an integer. Anything with a
273/// decimal exponent outside `-4..16` is written in exponent form with a signed two digit exponent,
274/// so `1e16` is `1e+16` and `0.00001` is `1e-05`, while `1e15` is still written out in full. That
275/// is C's `%g` rule and it is what DuckDB's formatter implements, checked against the binary rather
276/// than read out of its source.
277fn write_float<T: Real>(f: &mut fmt::Formatter<'_>, value: T) -> fmt::Result {
278    if value.is_nan() {
279        return f.write_str("nan");
280    }
281    if value.is_infinite() {
282        return f.write_str(if value.is_sign_negative() { "-inf" } else { "inf" });
283    }
284    let scientific = format!("{value:e}");
285    let (mantissa, exponent) = scientific.split_once('e').unwrap_or((scientific.as_str(), "0"));
286    let exponent: i32 = exponent.parse().unwrap_or(0);
287    if (-4..16).contains(&exponent) {
288        let text = format!("{value}");
289        if text.contains('.') {
290            return f.write_str(&text);
291        }
292        return write!(f, "{text}.0");
293    }
294    let sign = if exponent < 0 { '-' } else { '+' };
295    write!(f, "{mantissa}e{sign}{:02}", exponent.abs())
296}
297
298fn write_decimal(f: &mut fmt::Formatter<'_>, unscaled: i128, scale: u8) -> fmt::Result {
299    if scale == 0 {
300        return write!(f, "{unscaled}");
301    }
302    let negative = unscaled < 0;
303    // Widened before the negation so that i128::MIN does not overflow on the way to its digits.
304    let digits = unscaled.unsigned_abs().to_string();
305    let scale = usize::from(scale);
306    let (whole, fraction) = if digits.len() > scale {
307        let split = digits.len() - scale;
308        (digits[..split].to_string(), digits[split..].to_string())
309    } else {
310        ("0".to_string(), format!("{:0>scale$}", digits))
311    };
312    if negative {
313        f.write_str("-")?;
314    }
315    write!(f, "{whole}.{fraction}")
316}
317
318/// A blob prints as printable ASCII with everything else hex escaped, which is DuckDB's rule.
319///
320/// Three printable characters are escaped anyway, and they are the three that would otherwise make
321/// the printed form ambiguous: a backslash because it starts an escape, and the two quotes because
322/// the text this prints into is a string literal often enough. Every byte of all 256 was compared
323/// against DuckDB and these three were the only disagreement.
324fn write_blob(f: &mut fmt::Formatter<'_>, bytes: &[u8]) -> fmt::Result {
325    for &byte in bytes {
326        if (byte.is_ascii_graphic() || byte == b' ') && !matches!(byte, b'\\' | b'\'' | b'"') {
327            write!(f, "{}", byte as char)?;
328        } else {
329            write!(f, "\\x{byte:02X}")?;
330        }
331    }
332    Ok(())
333}
334
335/// Days since the epoch to the civil date, by Howard Hinnant's algorithm.
336///
337/// Written out rather than pulled in from a date library because it is twenty lines, because the
338/// dependency table in `spec/18-package-layout.md` is short on purpose, and because a date library
339/// that disagrees with DuckDB about a date before 1582 is a compatibility bug we would then own
340/// without being able to fix it.
341#[must_use]
342pub fn civil_from_days(days: i32) -> (i32, u32, u32) {
343    let z = i64::from(days) + 719_468;
344    let era = if z >= 0 { z } else { z - 146_096 } / 146_097;
345    let day_of_era = z - era * 146_097;
346    let year_of_era =
347        (day_of_era - day_of_era / 1460 + day_of_era / 36_524 - day_of_era / 146_096) / 365;
348    let year = year_of_era + era * 400;
349    let day_of_year = day_of_era - (365 * year_of_era + year_of_era / 4 - year_of_era / 100);
350    let shifted_month = (5 * day_of_year + 2) / 153;
351    let day = day_of_year - (153 * shifted_month + 2) / 5 + 1;
352    let month = if shifted_month < 10 { shifted_month + 3 } else { shifted_month - 9 };
353    let year = if month <= 2 { year + 1 } else { year };
354    #[expect(clippy::cast_possible_truncation, reason = "the ranges are 1 to 12 and 1 to 31")]
355    (year as i32, month as u32, day as u32)
356}
357
358/// The civil date to days since the epoch, the inverse of [`civil_from_days`].
359#[must_use]
360pub fn days_from_civil(year: i32, month: u32, day: u32) -> i32 {
361    let year = i64::from(year) - i64::from(month <= 2);
362    let era = if year >= 0 { year } else { year - 399 } / 400;
363    let year_of_era = year - era * 400;
364    let month = i64::from(month);
365    let shifted_month = if month > 2 { month - 3 } else { month + 9 };
366    let day_of_year = (153 * shifted_month + 2) / 5 + i64::from(day) - 1;
367    let day_of_era = year_of_era * 365 + year_of_era / 4 - year_of_era / 100 + day_of_year;
368    #[expect(clippy::cast_possible_truncation, reason = "a date in i32 range stays in i32 range")]
369    ((era * 146_097 + day_of_era - 719_468) as i32)
370}
371
372fn write_date(f: &mut fmt::Formatter<'_>, days: i32) -> fmt::Result {
373    let (year, month, day) = civil_from_days(days);
374    if year < 0 {
375        write!(f, "{:04}-{month:02}-{day:02} (BC)", -year + 1)
376    } else {
377        write!(f, "{year:04}-{month:02}-{day:02}")
378    }
379}
380
381fn write_time(f: &mut fmt::Formatter<'_>, micros: i64) -> fmt::Result {
382    let seconds = micros.div_euclid(1_000_000);
383    let fraction = micros.rem_euclid(1_000_000);
384    let (hours, minutes, seconds) = (seconds / 3600, (seconds / 60) % 60, seconds % 60);
385    write!(f, "{hours:02}:{minutes:02}:{seconds:02}")?;
386    if fraction != 0 {
387        // Trailing zeros are trimmed, so a value on a millisecond boundary prints three digits.
388        let text = format!("{fraction:06}");
389        write!(f, ".{}", text.trim_end_matches('0'))?;
390    }
391    Ok(())
392}
393
394fn write_timestamp(f: &mut fmt::Formatter<'_>, micros: i64) -> fmt::Result {
395    const MICROS_PER_DAY: i64 = 86_400 * 1_000_000;
396    let days = micros.div_euclid(MICROS_PER_DAY);
397    let within_day = micros.rem_euclid(MICROS_PER_DAY);
398    let Ok(days) = i32::try_from(days) else {
399        return f.write_str("timestamp out of range");
400    };
401    write_date(f, days)?;
402    f.write_str(" ")?;
403    write_time(f, within_day)
404}
405
406fn write_interval(f: &mut fmt::Formatter<'_>, months: i32, days: i32, micros: i64) -> fmt::Result {
407    let mut wrote = false;
408    let space = |f: &mut fmt::Formatter<'_>, wrote: &mut bool| -> fmt::Result {
409        if *wrote {
410            f.write_str(" ")?;
411        }
412        *wrote = true;
413        Ok(())
414    };
415    let (years, rest_months) = (months / 12, months % 12);
416    if years != 0 {
417        space(f, &mut wrote)?;
418        write!(f, "{years} year{}", plural(years))?;
419    }
420    if rest_months != 0 {
421        space(f, &mut wrote)?;
422        write!(f, "{rest_months} month{}", plural(rest_months))?;
423    }
424    if days != 0 {
425        space(f, &mut wrote)?;
426        write!(f, "{days} day{}", plural(days))?;
427    }
428    if micros != 0 || !wrote {
429        space(f, &mut wrote)?;
430        if micros < 0 {
431            f.write_str("-")?;
432        }
433        write_time(f, micros.abs())?;
434    }
435    Ok(())
436}
437
438fn plural(n: i32) -> &'static str {
439    if n == 1 || n == -1 { "" } else { "s" }
440}
441
442#[cfg(test)]
443mod tests {
444    use super::{Value, civil_from_days, days_from_civil};
445    use crate::types::LogicalType;
446
447    #[test]
448    fn a_value_knows_its_own_type() {
449        assert_eq!(Value::Integer(1).logical_type(), LogicalType::Integer);
450        assert_eq!(Value::Null.logical_type(), LogicalType::Null);
451        let list = Value::List { element: LogicalType::Varchar, values: Vec::new() };
452        // The element type is carried rather than inferred, which is why an empty list still
453        // knows what it is empty of.
454        assert_eq!(list.logical_type(), LogicalType::list(LogicalType::Varchar));
455    }
456
457    #[test]
458    fn the_date_conversion_is_its_own_inverse() {
459        // Every day from 1600 to 2400, which covers the Gregorian corrections and both signs of
460        // the era arithmetic. Cheap enough to be exhaustive, so it is exhaustive.
461        for days in days_from_civil(1600, 1, 1)..days_from_civil(2400, 1, 1) {
462            let (year, month, day) = civil_from_days(days);
463            assert_eq!(days_from_civil(year, month, day), days, "{year}-{month}-{day}");
464        }
465    }
466
467    #[test]
468    fn the_epoch_is_where_it_should_be() {
469        assert_eq!(days_from_civil(1970, 1, 1), 0);
470        assert_eq!(civil_from_days(0), (1970, 1, 1));
471        assert_eq!(Value::Date(0).to_string(), "1970-01-01");
472        assert_eq!(Value::Date(19_723).to_string(), "2024-01-01");
473        assert_eq!(Value::Date(19_737).to_string(), "2024-01-15");
474    }
475
476    #[test]
477    fn a_leap_day_is_a_day() {
478        assert_eq!(civil_from_days(days_from_civil(2024, 2, 29)), (2024, 2, 29));
479        // 1900 was not a leap year and 2000 was, which is the pair every naive implementation
480        // gets wrong in one direction or the other.
481        assert_eq!(days_from_civil(1900, 3, 1) - days_from_civil(1900, 2, 28), 1);
482        assert_eq!(days_from_civil(2000, 3, 1) - days_from_civil(2000, 2, 28), 2);
483    }
484
485    #[test]
486    fn times_print_with_the_trailing_zeros_trimmed() {
487        assert_eq!(Value::Time(0).to_string(), "00:00:00");
488        assert_eq!(Value::Time(3_723_000_000).to_string(), "01:02:03");
489        assert_eq!(Value::Time(3_723_500_000).to_string(), "01:02:03.5");
490        assert_eq!(Value::Time(3_723_000_001).to_string(), "01:02:03.000001");
491    }
492
493    #[test]
494    fn a_timestamp_before_the_epoch_borrows_from_the_day() {
495        // The whole reason this uses div_euclid rather than a plain divide. A negative microsecond
496        // count is the previous day at a positive time, not the next day at a negative one.
497        assert_eq!(Value::Timestamp(-1).to_string(), "1969-12-31 23:59:59.999999");
498        assert_eq!(Value::Timestamp(0).to_string(), "1970-01-01 00:00:00");
499    }
500
501    #[test]
502    fn a_decimal_prints_at_its_scale() {
503        let d = |unscaled, scale| Value::Decimal { unscaled, width: 18, scale }.to_string();
504        assert_eq!(d(1234, 2), "12.34");
505        assert_eq!(d(-1234, 2), "-12.34");
506        assert_eq!(d(5, 3), "0.005");
507        assert_eq!(d(-5, 3), "-0.005");
508        assert_eq!(d(1234, 0), "1234");
509        assert_eq!(d(1_000_000, 6), "1.000000");
510    }
511
512    #[test]
513    fn a_float_keeps_the_point_that_says_it_is_one() {
514        assert_eq!(Value::Double(1.0).to_string(), "1.0");
515        assert_eq!(Value::Double(-3.0).to_string(), "-3.0");
516        assert_eq!(Value::Double(1.5).to_string(), "1.5");
517        assert_eq!(Value::Double(-0.0).to_string(), "-0.0");
518        assert_eq!(Value::Float(0.5).to_string(), "0.5");
519    }
520
521    #[test]
522    fn a_float_is_printed_from_its_own_width_rather_than_widened_first() {
523        // 0.1f32 as an f64 is 0.10000000149011612, and printing that would be a real bug rather
524        // than a rounding difference, so this is the test that pins it.
525        assert_eq!(Value::Float(0.1).to_string(), "0.1");
526        assert_eq!(Value::Float(1.0).to_string(), "1.0");
527    }
528
529    #[test]
530    fn a_float_switches_to_an_exponent_where_duckdb_switches() {
531        assert_eq!(Value::Double(1e15).to_string(), "1000000000000000.0");
532        assert_eq!(Value::Double(1e16).to_string(), "1e+16");
533        assert_eq!(Value::Double(1e20).to_string(), "1e+20");
534        assert_eq!(Value::Double(1e-4).to_string(), "0.0001");
535        assert_eq!(Value::Double(1e-5).to_string(), "1e-05");
536        assert_eq!(Value::Double(1.234_567_890_123_456_8e17).to_string(), "1.2345678901234568e+17");
537    }
538
539    #[test]
540    fn a_float_that_is_not_a_number_says_so_the_way_duckdb_says_it() {
541        assert_eq!(Value::Double(f64::INFINITY).to_string(), "inf");
542        assert_eq!(Value::Double(f64::NEG_INFINITY).to_string(), "-inf");
543        assert_eq!(Value::Double(f64::NAN).to_string(), "nan");
544    }
545
546    #[test]
547    fn an_interval_keeps_months_days_and_micros_apart() {
548        let i = |months, days, micros| Value::Interval { months, days, micros }.to_string();
549        assert_eq!(i(14, 3, 3_723_000_000), "1 year 2 months 3 days 01:02:03");
550        assert_eq!(i(1, 0, 0), "1 month");
551        assert_eq!(i(0, 0, 0), "00:00:00");
552        assert_eq!(i(0, 0, -1_000_000), "-00:00:01");
553    }
554
555    #[test]
556    fn a_blob_escapes_what_is_not_printable() {
557        assert_eq!(Value::Blob(b"ok".to_vec()).to_string(), "ok");
558        assert_eq!(Value::Blob(vec![0, 1, b'a']).to_string(), "\\x00\\x01a");
559        assert_eq!(Value::Blob(vec![0x7f, 0xff]).to_string(), "\\x7F\\xFF");
560        // The three printable ones DuckDB escapes anyway, and the neighbours that it does not.
561        assert_eq!(Value::Blob(br#"'"\"#.to_vec()).to_string(), "\\x27\\x22\\x5C");
562        assert_eq!(Value::Blob(b" &`~".to_vec()).to_string(), " &`~");
563    }
564
565    #[test]
566    fn a_limit_that_does_not_fit_is_none_rather_than_clamped() {
567        assert_eq!(Value::Integer(5).as_i64(), Some(5));
568        assert_eq!(Value::UBigInt(u64::MAX).as_i64(), None);
569        assert_eq!(Value::Varchar("5".into()).as_i64(), None);
570    }
571}