Trait duckdb::vtab::VTab

source ·

pub trait VTab: Sized {
    type InitData: Sized + Free;
    type BindData: Sized + Free;

    // Required methods
    unsafe fn bind(
        bind: &BindInfo,
        data: *mut Self::BindData
    ) -> Result<(), Box<dyn Error>>;
    unsafe fn init(
        init: &InitInfo,
        data: *mut Self::InitData
    ) -> Result<(), Box<dyn Error>>;
    unsafe fn func(
        func: &FunctionInfo,
        output: &mut DataChunk
    ) -> Result<(), Box<dyn Error>>;

    // Provided methods
    fn supports_pushdown() -> bool { ... }
    fn parameters() -> Option<Vec<LogicalType>> { ... }
    fn named_parameters() -> Option<Vec<(String, LogicalType)>> { ... }
}

Expand description

Duckdb table function trait

See to the HelloVTab example for more details https://duckdb.org/docs/api/c/table_functions

Required Associated Types§

source

type InitData: Sized + Free

The data type of the bind data

source

type BindData: Sized + Free

The data type of the init data

Required Methods§

source

unsafe fn bind( bind: &BindInfo, data: *mut Self::BindData ) -> Result<(), Box<dyn Error>>

Bind data to the table function

§Safety

This function is unsafe because it dereferences raw pointers (data) and manipulates the memory directly. The caller must ensure that:

The data pointer is valid and points to a properly initialized BindData instance.
The lifetime of data must outlive the execution of bind to avoid dangling pointers, especially since bind does not take ownership of data.
Concurrent access to data (if applicable) must be properly synchronized.
The bind object must be valid and correctly initialized.

source

unsafe fn init( init: &InitInfo, data: *mut Self::InitData ) -> Result<(), Box<dyn Error>>

Initialize the table function

§Safety

This function is unsafe because it performs raw pointer dereferencing on the data argument. The caller is responsible for ensuring that:

The data pointer is non-null and points to a valid InitData instance.
There is no data race when accessing data, meaning if data is accessed from multiple threads, proper synchronization is required.
The lifetime of data extends beyond the scope of this call to avoid use-after-free errors.

source

unsafe fn func( func: &FunctionInfo, output: &mut DataChunk ) -> Result<(), Box<dyn Error>>

The actual function

§Safety

This function is unsafe because it:

Dereferences multiple raw pointers (func to access init_info and bind_info).

The caller must ensure that:

All pointers (func, output, internal init_info, and bind_info) are valid and point to the expected types of data structures.
The init_info and bind_info data pointed to remains valid and is not freed until after this function completes.
No other threads are concurrently mutating the data pointed to by init_info and bind_info without proper synchronization.
The output parameter is correctly initialized and can safely be written to.