Trait Decode 

pub trait Decode<'r, DB>: Sized
where
    DB: Database,
{
    // Required method
    fn decode(
        value: <DB as Database>::ValueRef<'r>,
    ) -> Result<Self, Box<dyn Error + Send + Sync>>;
}

A type that can be decoded from the database.

How can I implement Decode?

A manual implementation of Decode can be useful when adding support for types externally to SQLx.

The following showcases how to implement Decode to be generic over Database. The implementation can be marginally simpler if you remove the DB type parameter and explicitly use the concrete ValueRef and TypeInfo types.

struct MyType;

// DB is the database driver
// `'r` is the lifetime of the `Row` being decoded
impl<'r, DB: Database> Decode<'r, DB> for MyType
where
    // we want to delegate some of the work to string decoding so let's make sure strings
    // are supported by the database
    &'r str: Decode<'r, DB>
{
    fn decode(
        value: <DB as Database>::ValueRef<'r>,
    ) -> Result<MyType, Box<dyn Error + 'static + Send + Sync>> {
        // the interface of ValueRef is largely unstable at the moment
        // so this is not directly implementable

        // however, you can delegate to a type that matches the format of the type you want
        // to decode (such as a UTF-8 string)

        let value = <&str as Decode<DB>>::decode(value)?;

        // now you can parse this into your type (assuming there is a `FromStr`)

        Ok(value.parse()?)
    }
}

Required Methods

fn decode( value: <DB as Database>::ValueRef<'r>, ) -> Result<Self, Box<dyn Error + Send + Sync>>

Decode a new value of this type using a raw value from the database.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl Decode<'_, Postgres> for bool

fn decode(value: PgValueRef<'_>) -> Result<bool, Box<dyn Error + Send + Sync>>

impl Decode<'_, Postgres> for f32

fn decode(value: PgValueRef<'_>) -> Result<f32, Box<dyn Error + Send + Sync>>

impl Decode<'_, Postgres> for f64

fn decode(value: PgValueRef<'_>) -> Result<f64, Box<dyn Error + Send + Sync>>

impl Decode<'_, Postgres> for i8

fn decode(value: PgValueRef<'_>) -> Result<i8, Box<dyn Error + Send + Sync>>

impl Decode<'_, Postgres> for i16

fn decode(value: PgValueRef<'_>) -> Result<i16, Box<dyn Error + Send + Sync>>

impl Decode<'_, Postgres> for i32

fn decode(value: PgValueRef<'_>) -> Result<i32, Box<dyn Error + Send + Sync>>

impl Decode<'_, Postgres> for i64

fn decode(value: PgValueRef<'_>) -> Result<i64, Box<dyn Error + Send + Sync>>

impl Decode<'_, Postgres> for Box<[u8]>

fn decode( value: PgValueRef<'_>, ) -> Result<Box<[u8]>, Box<dyn Error + Send + Sync>>

impl Decode<'_, Postgres> for String

fn decode(value: PgValueRef<'_>) -> Result<String, Box<dyn Error + Send + Sync>>

impl Decode<'_, Postgres> for Vec<u8>

fn decode( value: PgValueRef<'_>, ) -> Result<Vec<u8>, Box<dyn Error + Send + Sync>>

impl Decode<'_, Postgres> for PgCiText

fn decode( value: PgValueRef<'_>, ) -> Result<PgCiText, Box<dyn Error + Send + Sync>>

impl Decode<'_, Postgres> for PgMoney

fn decode( value: PgValueRef<'_>, ) -> Result<PgMoney, Box<dyn Error + Send + Sync>>

impl Decode<'_, Postgres> for Oid

fn decode(value: PgValueRef<'_>) -> Result<Oid, Box<dyn Error + Send + Sync>>

impl<'a> Decode<'a, Any> for &'a str

fn decode( value: <Any as Database>::ValueRef<'a>, ) -> Result<&'a str, Box<dyn Error + Send + Sync>>

impl<'de> Decode<'de, Postgres> for PgInterval

fn decode( value: PgValueRef<'de>, ) -> Result<PgInterval, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Postgres> for &'r str

fn decode( value: PgValueRef<'r>, ) -> Result<&'r str, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Postgres> for &'r [u8]

fn decode( value: PgValueRef<'r>, ) -> Result<&'r [u8], Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Postgres> for Cow<'r, str>

fn decode( value: PgValueRef<'r>, ) -> Result<Cow<'r, str>, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Postgres> for PgCube

fn decode(value: PgValueRef<'r>) -> Result<PgCube, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Postgres> for ()

fn decode(_value: PgValueRef<'r>) -> Result<(), Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Postgres> for Box<str>

fn decode( value: PgValueRef<'r>, ) -> Result<Box<str>, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Postgres> for PgBox

fn decode(value: PgValueRef<'r>) -> Result<PgBox, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Postgres> for PgCircle

fn decode( value: PgValueRef<'r>, ) -> Result<PgCircle, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Postgres> for PgLine

fn decode(value: PgValueRef<'r>) -> Result<PgLine, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Postgres> for PgLSeg

fn decode(value: PgValueRef<'r>) -> Result<PgLSeg, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Postgres> for PgPath

fn decode(value: PgValueRef<'r>) -> Result<PgPath, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Postgres> for PgPoint

fn decode( value: PgValueRef<'r>, ) -> Result<PgPoint, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Postgres> for PgPolygon

fn decode( value: PgValueRef<'r>, ) -> Result<PgPolygon, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Postgres> for PgHstore

fn decode( value: PgValueRef<'r>, ) -> Result<PgHstore, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Postgres> for PgLQuery

fn decode( value: PgValueRef<'r>, ) -> Result<PgLQuery, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Postgres> for PgLTree

fn decode( value: PgValueRef<'r>, ) -> Result<PgLTree, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Postgres> for PgTimeTz

fn decode( value: PgValueRef<'r>, ) -> Result<PgTimeTz, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Any> for &'r [u8]

fn decode( value: <Any as Database>::ValueRef<'r>, ) -> Result<&'r [u8], Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Any> for bool

fn decode( value: <Any as Database>::ValueRef<'r>, ) -> Result<bool, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Any> for f32

fn decode(value: AnyValueRef<'r>) -> Result<f32, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Any> for f64

fn decode( value: <Any as Database>::ValueRef<'r>, ) -> Result<f64, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Any> for i16

fn decode( value: <Any as Database>::ValueRef<'r>, ) -> Result<i16, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Any> for i32

fn decode( value: <Any as Database>::ValueRef<'r>, ) -> Result<i32, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Any> for i64

fn decode( value: <Any as Database>::ValueRef<'r>, ) -> Result<i64, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Any> for String

fn decode( value: <Any as Database>::ValueRef<'r>, ) -> Result<String, Box<dyn Error + Send + Sync>>

impl<'r> Decode<'r, Any> for Vec<u8>

fn decode( value: <Any as Database>::ValueRef<'r>, ) -> Result<Vec<u8>, Box<dyn Error + Send + Sync>>

impl<'r, DB> Decode<'r, DB> for NonZero<i8>

where DB: Database, i8: Decode<'r, DB>,

fn decode( value: <DB as Database>::ValueRef<'r>, ) -> Result<NonZero<i8>, Box<dyn Error + Send + Sync>>

impl<'r, DB> Decode<'r, DB> for NonZero<i16>

where DB: Database, i16: Decode<'r, DB>,

fn decode( value: <DB as Database>::ValueRef<'r>, ) -> Result<NonZero<i16>, Box<dyn Error + Send + Sync>>

impl<'r, DB> Decode<'r, DB> for NonZero<i32>

where DB: Database, i32: Decode<'r, DB>,

fn decode( value: <DB as Database>::ValueRef<'r>, ) -> Result<NonZero<i32>, Box<dyn Error + Send + Sync>>

impl<'r, DB> Decode<'r, DB> for NonZero<i64>

where DB: Database, i64: Decode<'r, DB>,

fn decode( value: <DB as Database>::ValueRef<'r>, ) -> Result<NonZero<i64>, Box<dyn Error + Send + Sync>>

impl<'r, DB> Decode<'r, DB> for NonZero<u8>

where DB: Database, u8: Decode<'r, DB>,

fn decode( value: <DB as Database>::ValueRef<'r>, ) -> Result<NonZero<u8>, Box<dyn Error + Send + Sync>>

impl<'r, DB> Decode<'r, DB> for NonZero<u16>

where DB: Database, u16: Decode<'r, DB>,

fn decode( value: <DB as Database>::ValueRef<'r>, ) -> Result<NonZero<u16>, Box<dyn Error + Send + Sync>>

impl<'r, DB> Decode<'r, DB> for NonZero<u32>

where DB: Database, u32: Decode<'r, DB>,

fn decode( value: <DB as Database>::ValueRef<'r>, ) -> Result<NonZero<u32>, Box<dyn Error + Send + Sync>>

impl<'r, DB> Decode<'r, DB> for NonZero<u64>

where DB: Database, u64: Decode<'r, DB>,

fn decode( value: <DB as Database>::ValueRef<'r>, ) -> Result<NonZero<u64>, Box<dyn Error + Send + Sync>>

impl<'r, DB, T> Decode<'r, DB> for Option<T>

where DB: Database, T: Decode<'r, DB>,

fn decode( value: <DB as Database>::ValueRef<'r>, ) -> Result<Option<T>, Box<dyn Error + Send + Sync>>

impl<'r, T1> Decode<'r, Postgres> for (T1,)

where T1: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>,

fn decode(value: PgValueRef<'r>) -> Result<(T1,), Box<dyn Error + Send + Sync>>

impl<'r, T1, T2> Decode<'r, Postgres> for (T1, T2)

where T1: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T2: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>,

fn decode( value: PgValueRef<'r>, ) -> Result<(T1, T2), Box<dyn Error + Send + Sync>>

impl<'r, T1, T2, T3> Decode<'r, Postgres> for (T1, T2, T3)

where T1: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T2: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T3: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>,

fn decode( value: PgValueRef<'r>, ) -> Result<(T1, T2, T3), Box<dyn Error + Send + Sync>>

impl<'r, T1, T2, T3, T4> Decode<'r, Postgres> for (T1, T2, T3, T4)

where T1: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T2: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T3: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T4: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>,

fn decode( value: PgValueRef<'r>, ) -> Result<(T1, T2, T3, T4), Box<dyn Error + Send + Sync>>

impl<'r, T1, T2, T3, T4, T5> Decode<'r, Postgres> for (T1, T2, T3, T4, T5)

where T1: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T2: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T3: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T4: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T5: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>,

fn decode( value: PgValueRef<'r>, ) -> Result<(T1, T2, T3, T4, T5), Box<dyn Error + Send + Sync>>

impl<'r, T1, T2, T3, T4, T5, T6> Decode<'r, Postgres> for (T1, T2, T3, T4, T5, T6)

where T1: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T2: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T3: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T4: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T5: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T6: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>,

fn decode( value: PgValueRef<'r>, ) -> Result<(T1, T2, T3, T4, T5, T6), Box<dyn Error + Send + Sync>>

impl<'r, T1, T2, T3, T4, T5, T6, T7> Decode<'r, Postgres> for (T1, T2, T3, T4, T5, T6, T7)

where T1: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T2: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T3: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T4: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T5: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T6: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T7: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>,

fn decode( value: PgValueRef<'r>, ) -> Result<(T1, T2, T3, T4, T5, T6, T7), Box<dyn Error + Send + Sync>>

impl<'r, T1, T2, T3, T4, T5, T6, T7, T8> Decode<'r, Postgres> for (T1, T2, T3, T4, T5, T6, T7, T8)

where T1: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T2: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T3: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T4: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T5: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T6: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T7: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T8: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>,

fn decode( value: PgValueRef<'r>, ) -> Result<(T1, T2, T3, T4, T5, T6, T7, T8), Box<dyn Error + Send + Sync>>

impl<'r, T1, T2, T3, T4, T5, T6, T7, T8, T9> Decode<'r, Postgres> for (T1, T2, T3, T4, T5, T6, T7, T8, T9)

where T1: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T2: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T3: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T4: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T5: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T6: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T7: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T8: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>, T9: 'r + Type<Postgres> + for<'a> Decode<'a, Postgres>,

fn decode( value: PgValueRef<'r>, ) -> Result<(T1, T2, T3, T4, T5, T6, T7, T8, T9), Box<dyn Error + Send + Sync>>

impl<'r, T> Decode<'r, Postgres> for Vec<T>

where T: for<'a> Decode<'a, Postgres> + Type<Postgres>,

fn decode(value: PgValueRef<'r>) -> Result<Vec<T>, Box<dyn Error + Send + Sync>>

impl<'r, T> Decode<'r, Postgres> for PgRange<T>

where T: Type<Postgres> + for<'a> Decode<'a, Postgres>,

fn decode( value: PgValueRef<'r>, ) -> Result<PgRange<T>, Box<dyn Error + Send + Sync>>

impl<'r, T, const N: usize> Decode<'r, Postgres> for [T; N]

where T: for<'a> Decode<'a, Postgres> + Type<Postgres>,

fn decode(value: PgValueRef<'r>) -> Result<[T; N], Box<dyn Error + Send + Sync>>

impl<const N: usize> Decode<'_, Postgres> for [u8; N]

fn decode( value: PgValueRef<'_>, ) -> Result<[u8; N], Box<dyn Error + Send + Sync>>

Implementors

impl Decode<'_, Postgres> for Decimal

Note: rust_decimal::Decimal Has a Smaller Range than NUMERIC

NUMERIC is can have up to 131,072 digits before the decimal point, and 16,384 digits after it. See [Section 8.1, Numeric Types] of the Postgres manual for details.

However, rust_decimal::Decimal is limited to a maximum absolute magnitude of 2⁹⁶ - 1, a number with 67 decimal digits, and a minimum absolute magnitude of 10^-28, a number with, unsurprisingly, 28 decimal digits.

Thus, in contrast with BigDecimal, NUMERIC can actually represent every possible value of rust_decimal::Decimal, but not the other way around. This means that encoding should never fail, but decoding can.

impl Decode<'_, Postgres> for Uuid

impl<'r> Decode<'r, Postgres> for DateTime<FixedOffset>

impl<'r> Decode<'r, Postgres> for DateTime<Local>

impl<'r> Decode<'r, Postgres> for DateTime<Utc>

impl<'r> Decode<'r, Postgres> for NaiveDate

impl<'r> Decode<'r, Postgres> for NaiveDateTime

impl<'r> Decode<'r, Postgres> for NaiveTime

impl<'r, DB> Decode<'r, DB> for &'r RawValue

where Json<&'r RawValue>: Decode<'r, DB>, DB: Database,

impl<'r, DB> Decode<'r, DB> for Value

where Json<Value>: Decode<'r, DB>, DB: Database,

impl<'r, T> Decode<'r, Postgres> for Json<T>

where T: 'r + Deserialize<'r>,

impl<'r, T> Decode<'r, Postgres> for Text<T>

where T: FromStr, Box<dyn Error + Send + Sync>: From<<T as FromStr>::Err>,