Struct FFI_TableProvider 

#[repr(C)]
pub struct FFI_TableProvider {
    pub schema: unsafe extern "C" fn(provider: &Self) -> WrappedSchema,
    pub scan: unsafe extern "C" fn(provider: &Self, session_config: &FFI_SessionConfig, projections: RVec<usize>, filters_serialized: RVec<u8>, limit: ROption<usize>) -> FfiFuture<RResult<FFI_ExecutionPlan, RString>>,
    pub table_type: unsafe extern "C" fn(provider: &Self) -> FFI_TableType,
    pub supports_filters_pushdown: Option<unsafe extern "C" fn(provider: &FFI_TableProvider, filters_serialized: RVec<u8>) -> RResult<RVec<FFI_TableProviderFilterPushDown>, RString>>,
    pub insert_into: unsafe extern "C" fn(provider: &Self, session_config: &FFI_SessionConfig, input: &FFI_ExecutionPlan, insert_op: FFI_InsertOp) -> FfiFuture<RResult<FFI_ExecutionPlan, RString>>,
    pub clone: unsafe extern "C" fn(plan: &Self) -> Self,
    pub release: unsafe extern "C" fn(arg: &mut Self),
    pub version: unsafe extern "C" fn() -> u64,
    pub private_data: *mut c_void,
}

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

schema: unsafe extern "C" fn(provider: &Self) -> WrappedSchema

Return the table schema

scan: unsafe extern "C" fn(provider: &Self, session_config: &FFI_SessionConfig, projections: RVec<usize>, filters_serialized: RVec<u8>, limit: ROption<usize>) -> FfiFuture<RResult<FFI_ExecutionPlan, RString>>

Perform a scan on the table. See TableProvider for detailed usage information.

Arguments

• provider - the table provider
• session_config - session configuration
• projections - if specified, only a subset of the columns are returned
• filters_serialized - filters to apply to the scan, which are a LogicalExprList protobuf message serialized into bytes to pass across the FFI boundary.
• limit - if specified, limit the number of rows returned

table_type: unsafe extern "C" fn(provider: &Self) -> FFI_TableType

Return the type of table. See TableType for options.

supports_filters_pushdown: Option<unsafe extern "C" fn(provider: &FFI_TableProvider, filters_serialized: RVec<u8>) -> RResult<RVec<FFI_TableProviderFilterPushDown>, RString>>

Based upon the input filters, identify which are supported. The filters are a LogicalExprList protobuf message serialized into bytes to pass across the FFI boundary.

insert_into: unsafe extern "C" fn(provider: &Self, session_config: &FFI_SessionConfig, input: &FFI_ExecutionPlan, insert_op: FFI_InsertOp) -> FfiFuture<RResult<FFI_ExecutionPlan, RString>>

clone: unsafe extern "C" fn(plan: &Self) -> Self

Used to create a clone on the provider of the execution plan. This should only need to be called by the receiver of the plan.

release: unsafe extern "C" fn(arg: &mut Self)

Release the memory of the private data when it is no longer being used.

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

Return the major DataFusion version number of this provider.

private_data: *mut c_void

Internal data. This is only to be accessed by the provider of the plan. A ForeignExecutionPlan should never attempt to access this data.

Implementations

impl FFI_TableProvider

pub fn new( provider: Arc<dyn TableProvider + Send>, can_support_pushdown_filters: bool, runtime: Option<Handle>, ) -> Self

Creates a new FFI_TableProvider.

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.

impl From<&FFI_TableProvider> for ForeignTableProvider

fn from(provider: &FFI_TableProvider) -> Self

Converts to this type from the input type.

impl GetStaticEquivalent_ for FFI_TableProvider

type StaticEquivalent = _static_FFI_TableProvider

The 'static equivalent of Self

impl StableAbi for FFI_TableProvider

const LAYOUT: &'static TypeLayout

The layout of the type provided by implementors.

type IsNonZeroType = False

Whether this type has a single invalid bit-pattern.

const ABI_CONSTS: AbiConsts = _

const-equivalents of the associated types.

impl Send for FFI_TableProvider

impl Sync for FFI_TableProvider