Trait pgx::datum::FromDatum

pub trait FromDatum {
    pub unsafe fn from_datum(
        datum: Datum, 
        is_null: bool, 
        typoid: Oid
    ) -> Option<Self>
    where
        Self: Sized;

    pub unsafe fn from_datum_in_memory_context(
        mut memory_context: PgMemoryContexts, 
        datum: Datum, 
        is_null: bool, 
        typoid: Oid
    ) -> Option<Self>
    where
        Self: Sized,
    { ... }
}

Convert a (pg_sys::Datum, is_null:bool, type_oid:pg_sys::Oid) tuple into a Rust type

Default implementations are provided for the common Rust types.

If implementing this, also implement IntoDatum for the reverse conversion.

Required methods

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    typoid: Oid
) -> Option<Self> where
    Self: Sized, 

Safety

This method is inherently unsafe as the datum argument can represent an arbitrary memory address in the case of pass-by-reference Datums. Referencing that memory address can cause Postgres to crash if it's invalid.

If the (datum, is_null) tuple comes from Postgres, it's generally okay to consider this a safe call (ie, wrap it in unsafe {}) and move on with life.

If, however, you're providing an arbitrary datum value, it needs to be considered unsafe and that unsafeness should be propagated through your API.

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Provided methods

pub unsafe fn from_datum_in_memory_context(
    mut memory_context: PgMemoryContexts,
    datum: Datum,
    is_null: bool,
    typoid: Oid
) -> Option<Self> where
    Self: Sized, 

Default implementation switched to the specified memory context and then simply calls From::from_datum(...) from within that context.

For certain Datums (such as &str), this is likely not enough and this function should be overridden in the type's trait implementation.

The intent here is that the returned Rust type, which might be backed by a pass-by-reference Datum, be copied into the specified memory context, and then the Rust type constructed from that pointer instead.

Safety

Same caveats as From::from_datum(...)

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Implementations on Foreign Types

impl<T: FromDatum> FromDatum for Vec<T>

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    typoid: Oid
) -> Option<Vec<T>>

impl<T: FromDatum> FromDatum for Vec<Option<T>>

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    typoid: Oid
) -> Option<Vec<Option<T>>>

impl FromDatum for Datum

for pg_sys::Datum

pub unsafe fn from_datum(datum: Datum, is_null: bool, _: Oid) -> Option<Datum>

impl FromDatum for bool

for bool

pub unsafe fn from_datum(datum: Datum, is_null: bool, _: Oid) -> Option<bool>

impl FromDatum for i8

for "char"

pub unsafe fn from_datum(datum: Datum, is_null: bool, _: Oid) -> Option<i8>

impl FromDatum for i16

for smallint

pub unsafe fn from_datum(datum: Datum, is_null: bool, _: Oid) -> Option<i16>

impl FromDatum for i32

for integer

pub unsafe fn from_datum(datum: Datum, is_null: bool, _: Oid) -> Option<i32>

impl FromDatum for u32

for oid

pub unsafe fn from_datum(datum: Datum, is_null: bool, _: Oid) -> Option<u32>

impl FromDatum for i64

for bigint

pub unsafe fn from_datum(datum: Datum, is_null: bool, _: Oid) -> Option<i64>

impl FromDatum for f32

for real

pub unsafe fn from_datum(datum: Datum, is_null: bool, _: Oid) -> Option<f32>

impl FromDatum for f64

for double precision

pub unsafe fn from_datum(datum: Datum, is_null: bool, _: Oid) -> Option<f64>

impl<'a> FromDatum for &'a str

for text, varchar

pub unsafe fn from_datum(datum: Datum, is_null: bool, _: Oid) -> Option<&'a str>

pub unsafe fn from_datum_in_memory_context(
    mut memory_context: PgMemoryContexts,
    datum: usize,
    is_null: bool,
    _typoid: u32
) -> Option<Self> where
    Self: Sized, 

impl FromDatum for String

for text, varchar, or any pg_sys::varlena-based type

This returns a copy, allocated and managed by Rust, of the underlying varlena Datum

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    typoid: Oid
) -> Option<String>

impl FromDatum for char

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    typoid: Oid
) -> Option<char>

impl<'a> FromDatum for &'a CStr

for cstring

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    _: Oid
) -> Option<&'a CStr>

impl<'a> FromDatum for &'a [u8]

for bytea

pub unsafe fn from_datum(
    datum: usize,
    is_null: bool,
    _typoid: u32
) -> Option<&'a [u8]>

pub unsafe fn from_datum_in_memory_context(
    mut memory_context: PgMemoryContexts,
    datum: usize,
    is_null: bool,
    _typoid: u32
) -> Option<Self> where
    Self: Sized, 

impl FromDatum for Vec<u8>

pub unsafe fn from_datum(
    datum: usize,
    is_null: bool,
    typoid: u32
) -> Option<Vec<u8>>

impl FromDatum for ()

for NULL -- always converts to a None, even if the is_null argument is false

pub unsafe fn from_datum(_datum: Datum, _is_null: bool, _: Oid) -> Option<()>

impl FromDatum for BOX

pub unsafe fn from_datum(datum: Datum, is_null: bool, _: Oid) -> Option<Self> where
    Self: Sized, 

impl FromDatum for Point

pub unsafe fn from_datum(datum: Datum, is_null: bool, _: Oid) -> Option<Self> where
    Self: Sized, 

impl FromDatum for ItemPointerData

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    _typoid: u32
) -> Option<ItemPointerData>

impl<A, B> FromDatum for (Option<A>, Option<B>) where
    A: FromDatum + IntoDatum,
    B: FromDatum + IntoDatum, 

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    typoid: Oid
) -> Option<Self> where
    Self: Sized, 

impl<A, B, C> FromDatum for (Option<A>, Option<B>, Option<C>) where
    A: FromDatum + IntoDatum,
    B: FromDatum + IntoDatum,
    C: FromDatum + IntoDatum, 

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    typoid: Oid
) -> Option<Self> where
    Self: Sized, 

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Implementors

impl FromDatum for AnyArray

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    typoid: Oid
) -> Option<AnyArray>

impl FromDatum for AnyElement

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    typoid: Oid
) -> Option<AnyElement>

impl FromDatum for Date

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    _typoid: u32
) -> Option<Date>

impl FromDatum for Inet

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    _typoid: u32
) -> Option<Inet>

impl FromDatum for Json

for json

pub unsafe fn from_datum(datum: Datum, is_null: bool, _: Oid) -> Option<Json>

impl FromDatum for JsonB

for jsonb

pub unsafe fn from_datum(datum: Datum, is_null: bool, _: Oid) -> Option<JsonB>

impl FromDatum for JsonString

for json types to be represented as a wholly-owned Rust String copy

This returns a copy, allocated and managed by Rust, of the underlying varlena Datum

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    _: Oid
) -> Option<JsonString>

impl FromDatum for Numeric

pub unsafe fn from_datum(
    datum: usize,
    is_null: bool,
    _typoid: u32
) -> Option<Self> where
    Self: Sized, 

impl FromDatum for Time

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    _typoid: u32
) -> Option<Time>

impl FromDatum for TimeWithTimeZone

pub unsafe fn from_datum(
    datum: usize,
    is_null: bool,
    typoid: u32
) -> Option<TimeWithTimeZone>

impl FromDatum for Timestamp

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    typoid: u32
) -> Option<Timestamp>

impl FromDatum for TimestampWithTimeZone

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    _typoid: u32
) -> Option<TimestampWithTimeZone>

impl FromDatum for PgRelation

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    _typoid: u32
) -> Option<PgRelation>

impl<'a, T: FromDatum> FromDatum for Array<'a, T>

pub unsafe fn from_datum(
    datum: usize,
    is_null: bool,
    typoid: u32
) -> Option<Array<'a, T>>

impl<'de, T> FromDatum for T where
    T: PostgresType + Deserialize<'de>, 

pub unsafe fn from_datum(
    datum: usize,
    is_null: bool,
    _typoid: u32
) -> Option<Self>

pub unsafe fn from_datum_in_memory_context(
    memory_context: PgMemoryContexts,
    datum: usize,
    is_null: bool,
    _typoid: u32
) -> Option<Self>

impl<T> FromDatum for Internal<T>

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    _: Oid
) -> Option<Internal<T>>

impl<T> FromDatum for PgVarlena<T> where
    T: Copy + Sized, 

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    _typoid: u32
) -> Option<Self>

pub unsafe fn from_datum_in_memory_context(
    mut memory_context: PgMemoryContexts,
    datum: usize,
    is_null: bool,
    _typoid: u32
) -> Option<Self>

impl<T> FromDatum for PgBox<T>

for user types

pub unsafe fn from_datum(
    datum: Datum,
    is_null: bool,
    _: Oid
) -> Option<PgBox<T>>

pub unsafe fn from_datum_in_memory_context(
    mut memory_context: PgMemoryContexts,
    datum: usize,
    is_null: bool,
    _typoid: u32
) -> Option<Self> where
    Self: Sized, 

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