Trait WalFilter 

pub trait WalFilter: Send + Sync {
    // Required methods
    fn name(&self) -> &CStr;
    fn log_record_found(
        &self,
        log_number: u64,
        log_file_name: &[u8],
        batch: &WriteBatch,
        replacement: &mut WriteBatch,
    ) -> WalRecordAction;

    // Provided method
    fn column_family_log_number_map(
        &self,
        _cf_log_numbers: &ColumnFamilyLogNumbers<'_>,
    ) { ... }
}

A hook into WAL replay.

Implementations are shared: Options can be cloned and used to open several DBs, all of which point at the same filter, so the methods take &self and the trait requires Send + Sync. Reach for a Mutex or an atomic if the filter needs to accumulate state.

Panics

These methods are called from C++ across an extern "C" boundary, where an unwind is undefined behaviour. A panic that escapes any of them aborts the process instead. Return WalRecordAction::Corrupted to report a bad record.

Required Methods

fn name(&self) -> &CStr

Identifies this filter in the LOG file and in the error text RocksDB produces when the filter reports corruption.

The pointer behind the returned CStr is handed to C++ as is, so it has to stay valid for as long as the filter does. A field of self or a c"..." literal both work.

fn log_record_found( &self, log_number: u64, log_file_name: &[u8], batch: &WriteBatch, replacement: &mut WriteBatch, ) -> WalRecordAction

Called for each WAL record recovery reads.

batch is the record as written. replacement starts empty and is only looked at if this returns WalRecordAction::Replace, in which case it is replayed in place of batch and inherits the original’s sequence number.

log_file_name is the path of the log being read, for logging only. It is raw bytes because it is built from the DB path, which this crate passes through without validating it as UTF-8.

Provided Methods

fn column_family_log_number_map( &self, _cf_log_numbers: &ColumnFamilyLogNumbers<'_>, )

Called once before replay starts, with the flush position of every column family.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors