Trait Decode

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

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 HasValueRef<'r>>::ValueRef,
    ) -> 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 HasValueRef<'r>>::ValueRef, ) -> Result<Self, Box<dyn Error + Sync + Send>>

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 + Sync + Send>>

impl Decode<'_, Postgres> for f32

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

impl Decode<'_, Postgres> for f64

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

impl Decode<'_, Postgres> for i8

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

impl Decode<'_, Postgres> for i16

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

impl Decode<'_, Postgres> for i32

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

impl Decode<'_, Postgres> for i64

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

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

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

impl Decode<'_, Postgres> for String

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

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

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

impl Decode<'_, Sqlite> for Box<str>

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

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

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

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

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

impl<'db> Decode<'db, Postgres> for IpAddr

where IpNetwork: Decode<'db, Postgres>,

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

impl<'r> Decode<'r, Sqlite> for i8

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

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

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

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

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

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

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

impl<'r> Decode<'r, Sqlite> for u8

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

impl<'r> Decode<'r, Sqlite> for u16

fn decode( value: SqliteValueRef<'r>, ) -> Result<u16, Box<dyn Error + Sync + Send>>

impl<'r> Decode<'r, Sqlite> for u32

fn decode( value: SqliteValueRef<'r>, ) -> Result<u32, Box<dyn Error + Sync + Send>>

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

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

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

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

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

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

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

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 + Sync + Send>>

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 + Sync + Send>>

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 + Sync + Send>>

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 + Sync + Send>>

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 + Sync + Send>>

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 + Sync + Send>>

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 + Sync + Send>>

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 + Sync + Send>>

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 + Sync + Send>>

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 + Sync + Send>>

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 + Sync + Send>>

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

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

Implementors

impl Decode<'_, Postgres> for IpNetwork

impl Decode<'_, Postgres> for Oid

impl Decode<'_, Postgres> for PgCiText

impl Decode<'_, Postgres> for PgMoney

impl Decode<'_, Postgres> for MacAddress

impl Decode<'_, Postgres> for BigDecimal

Note: NaN

BigDecimal has a greater range than NUMERIC (see the corresponding Encode impl for details) but cannot represent NaN, so decoding may return an error.

impl Decode<'_, Postgres> for BitVec

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 Decode<'_, Sqlite> for Uuid

impl Decode<'_, Sqlite> for Hyphenated

impl Decode<'_, Sqlite> for Simple

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

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

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

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

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

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> Decode<'r, Postgres> for Date

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

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

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

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

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

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

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

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

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

impl<'r> Decode<'r, Sqlite> for Date

impl<'r> Decode<'r, Sqlite> for OffsetDateTime

impl<'r> Decode<'r, Sqlite> for PrimitiveDateTime

impl<'r> Decode<'r, Sqlite> for Time

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 PgRange<T>

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

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 + Sync + Send>: From<<T as FromStr>::Err>,

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

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

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

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