Trait pgrx::datum::FromDatum

pub trait FromDatum {
    const GET_TYPOID: bool = false;

    // Required method
    unsafe fn from_polymorphic_datum(
        datum: Datum,
        is_null: bool,
        typoid: Oid
    ) -> Option<Self>
       where Self: Sized;

    // Provided methods
    unsafe fn from_datum(datum: Datum, is_null: bool) -> Option<Self>
       where Self: Sized { ... }
    unsafe fn from_datum_in_memory_context(
        memory_context: PgMemoryContexts,
        datum: Datum,
        is_null: bool,
        typoid: Oid
    ) -> Option<Self>
       where Self: Sized { ... }
    unsafe fn try_from_datum(
        datum: Datum,
        is_null: bool,
        type_oid: Oid
    ) -> Result<Option<Self>, TryFromDatumError>
       where Self: Sized + IntoDatum { ... }
    unsafe fn try_from_datum_in_memory_context(
        memory_context: PgMemoryContexts,
        datum: Datum,
        is_null: bool,
        type_oid: Oid
    ) -> Result<Option<Self>, TryFromDatumError>
       where Self: Sized + IntoDatum { ... }
}

Convert a (pg_sys::Datum, is_null:bool) pair into a Rust type

Default implementations are provided for the common Rust types.

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

Provided Associated Constants

const GET_TYPOID: bool = false

Should a type OID be fetched when calling from_datum?

Required Methods

unsafe fn from_polymorphic_datum( datum: Datum, is_null: bool, typoid: Oid ) -> Option<Self>

where Self: Sized,

Like from_datum for instantiating polymorphic types which require preserving the dynamic type metadata.

Safety

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

Provided Methods

unsafe fn from_datum(datum: Datum, is_null: bool) -> 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) pair 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.

unsafe fn from_datum_in_memory_context( 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 FromDatum::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 FromDatum::from_datum(...)

unsafe fn try_from_datum( datum: Datum, is_null: bool, type_oid: Oid ) -> Result<Option<Self>, TryFromDatumError>

where Self: Sized + IntoDatum,

try_from_datum is a convenience wrapper around FromDatum::from_datum that returns a a Result around an Option, as a Datum can be null. It’s intended to be used in situations where the caller needs to know whether the type conversion succeeded or failed.

Safety

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

unsafe fn try_from_datum_in_memory_context( memory_context: PgMemoryContexts, datum: Datum, is_null: bool, type_oid: Oid ) -> Result<Option<Self>, TryFromDatumError>

where Self: Sized + IntoDatum,

A version of try_from_datum that switches to the given context to convert from Datum

Object Safety

This trait is not object safe.

Implementations on Foreign Types

impl FromDatum for bool

for bool

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

impl FromDatum for char

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

impl FromDatum for f32

for real

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

impl FromDatum for f64

for double precision

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

impl FromDatum for i8

for "char"

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

impl FromDatum for i16

for smallint

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

impl FromDatum for i32

for integer

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

impl FromDatum for i64

for bigint

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

impl FromDatum for u32

for oid

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

impl FromDatum for ()

for VOID – always converts to Some(()), even if the “is_null” argument is true

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

impl FromDatum for String

For Postgres text, varchar, or any pg_sys::varlena-based type

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

Note that while these conversions are inherently unsafe, they still enforce UTF-8 correctness, so they may panic if you use PGRX with a database that has non-UTF-8 data. The details of this are subject to change.

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

impl FromDatum for Vec<u8>

unsafe fn from_polymorphic_datum( datum: Datum, is_null: bool, typoid: Oid ) -> Option<Vec<u8>>

impl<'a> FromDatum for &'a str

For Postgres text and varchar

Note that while these conversions are inherently unsafe, they still enforce UTF-8 correctness, so they may panic if you use PGRX with a database that has non-UTF-8 data. The details of this are subject to change.

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

unsafe fn from_datum_in_memory_context( memory_context: PgMemoryContexts, datum: Datum, is_null: bool, _typoid: Oid ) -> Option<Self>

where Self: Sized,

impl<'a> FromDatum for &'a CStr

for cstring

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

unsafe fn from_datum_in_memory_context( memory_context: PgMemoryContexts, datum: Datum, is_null: bool, _typoid: Oid ) -> Option<Self>

where Self: Sized,

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

for bytea

unsafe fn from_polymorphic_datum( datum: Datum, is_null: bool, _typoid: Oid ) -> Option<&'a [u8]>

unsafe fn from_datum_in_memory_context( memory_context: PgMemoryContexts, datum: Datum, is_null: bool, _typoid: Oid ) -> Option<Self>

where Self: Sized,

impl<A, B> FromDatum for (Option<A>, Option<B>)

where A: FromDatum + IntoDatum, B: FromDatum + IntoDatum,

unsafe fn from_polymorphic_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,

unsafe fn from_polymorphic_datum( datum: Datum, is_null: bool, typoid: Oid ) -> Option<Self>

where Self: Sized,

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

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

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

where Self: Sized,

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

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

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

where Self: Sized,

Implementors

impl FromDatum for BOX

impl FromDatum for Datum

for pg_sys::Datum

impl FromDatum for ItemPointerData

impl FromDatum for Oid

impl FromDatum for Point

impl FromDatum for PgRelation

impl FromDatum for AnyNumeric

impl FromDatum for AnyArray

const GET_TYPOID: bool = true

impl FromDatum for AnyElement

const GET_TYPOID: bool = true

impl FromDatum for Date

impl FromDatum for Inet

impl FromDatum for Internal

impl FromDatum for Interval

impl FromDatum for Json

for json

impl FromDatum for JsonB

for 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

impl FromDatum for Time

impl FromDatum for TimeWithTimeZone

impl FromDatum for Timestamp

impl FromDatum for TimestampWithTimeZone

impl FromDatum for Uuid

impl<'a> FromDatum for PgHeapTuple<'a, AllocatedByRust>

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

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

impl<'de, T> FromDatum for T

where T: PostgresType + Deserialize<'de>,

impl<T> FromDatum for PgBox<T, AllocatedByPostgres>

for user types

impl<T> FromDatum for PgVarlena<T>

where T: Copy + Sized,

impl<T> FromDatum for Range<T>

where T: RangeSubType,

impl<const P: u32, const S: u32> FromDatum for Numeric<P, S>