Struct FFI_TableProvider 

pub struct FFI_TableProvider {
    pub statistics: unsafe extern "C" fn(provider: &Self) -> FFI_Option<Vec<u8>>,
    pub logical_codec: FFI_LogicalExtensionCodec,
    pub version: unsafe extern "C" fn() -> u64,
    pub library_marker_id: extern "C" fn() -> usize,
    /* private fields */
}

A stable struct for sharing TableProvider across FFI boundaries.

Struct Layout

The following description applies to all structs provided in this crate.

Each of the exposed structs in this crate is provided with a variant prefixed with Foreign. This variant is designed to be used by the consumer of the foreign code. The Foreign structs should never access the private_data fields. Instead they should only access the data returned through the function calls defined on the FFI_ structs. The second purpose of the Foreign structs is to contain additional data that may be needed by the traits that are implemented on them. Some of these traits require borrowing data which can be far more convenient to be locally stored.

For example, we have a struct FFI_TableProvider to give access to the TableProvider functions like table_type() and scan(). If we write a library that wishes to expose it’s TableProvider, then we can access the private data that contains the Arc reference to the TableProvider via FFI_TableProvider. This data is local to the library.

If we have a program that accesses a TableProvider via FFI, then it will use ForeignTableProvider. When using ForeignTableProvider we must not attempt to access the private_data field in FFI_TableProvider. If a user is testing locally, you may be able to successfully access this field, but it will only work if you are building against the exact same version of DataFusion for both libraries and the same compiler. It will not work in general.

It is worth noting that which library is the local and which is foreign depends on which interface we are considering. For example, suppose we have a Python library called my_provider that exposes a TableProvider called MyProvider via FFI_TableProvider. Within the library my_provider we can access the private_data via FFI_TableProvider. We connect this to datafusion-python, where we access it as a ForeignTableProvider. Now when we call scan() on this interface, we have to pass it a FFI_SessionConfig. The SessionConfig is local to datafusion-python and not my_provider. It is important to be careful when expanding these functions to be certain which side of the interface each object refers to.

Fields

statistics: unsafe extern "C" fn(provider: &Self) -> FFI_Option<Vec<u8>>

Snapshot the provider’s table-level statistics. FFI_Option::None corresponds to TableProvider::statistics returning None; Some(bytes) is a prost-encoded datafusion_proto_common::Statistics.

logical_codec: FFI_LogicalExtensionCodec

version: unsafe extern "C" fn() -> u64

Return the major DataFusion version number of this provider.

library_marker_id: extern "C" fn() -> usize

Utility to identify when FFI objects are accessed locally through the foreign interface. See crate::get_library_marker_id and the crate’s README.md for more information.

Implementations

impl FFI_TableProvider

pub fn new( provider: Arc<dyn TableProvider>, can_support_pushdown_filters: bool, runtime: Option<Handle>, task_ctx_provider: impl Into<FFI_TaskContextProvider>, logical_codec: Option<Arc<dyn LogicalExtensionCodec>>, ) -> Self

Creates a new FFI_TableProvider.

pub fn new_with_ffi_codec( provider: Arc<dyn TableProvider>, can_support_pushdown_filters: bool, runtime: Option<Handle>, logical_codec: FFI_LogicalExtensionCodec, ) -> Self

Trait Implementations

impl Clone for FFI_TableProvider

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for FFI_TableProvider

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Drop for FFI_TableProvider

fn drop(&mut self)

Executes the destructor for this type.

fn pin_drop(self: Pin<&mut Self>)

🔬This is a nightly-only experimental API. (pin_ergonomics)

Execute the destructor for this type, but different to Drop::drop, it requires self to be pinned.

impl From<&FFI_TableProvider> for Arc<dyn TableProvider>

fn from(provider: &FFI_TableProvider) -> Self

Converts to this type from the input type.

impl Send for FFI_TableProvider

impl Sync for FFI_TableProvider