Struct fdb_rl::cursor::limit_manager::LimitManager

pub(crate) struct LimitManager {
    scan_limiter: ScanLimiter,
    halted_due_to_keyvalue_scan_limit: bool,
    halted_due_to_byte_scan_limit: bool,
    halted_due_to_time_scan_limit: bool,
}

Handles the logic of tracking out-of-band limits.

Out-of-band limits are:

1. Keyvalue limit
2. Byte Limit
3. Time Limit

The limit manager merely tracks the limit state and provides coherent answers to the questions:

1. Can the cursor advance without exceeding the limit?
2. What limit has been exceeded?

Unlike Java RecordLayer, we do not have a notion of “free initial pass”. This is because in our cursor implementation, we can return a begin continuation in case a out-of-band limit was reached before the cursor could make any progress. The client can then return the begin continuation back and the cursor will start from the beginning.

Fields

scan_limiter: ScanLimiter

halted_due_to_keyvalue_scan_limit: bool

halted_due_to_byte_scan_limit: bool

halted_due_to_time_scan_limit: bool

Implementations

impl LimitManager

pub(crate) fn new(scan_limiter: ScanLimiter) -> LimitManager

Create a new LimitManager from a value of ScanLimiter.

pub(crate) fn try_keyvalue_scan( &mut self ) -> Result<(), LimitManagerStoppedReason>

Return true if keyvalue can be read otherwise return false.

If we have a Some(KeyValueScanLimiter) in ScanLimiter, it also increments its keyvalues_scanned field.

Used by <KeyValueCursor as Cursor<KeyValue>>::next.

pub(crate) fn register_scanned_bytes(&self, byte_size: usize)

Increment the number of bytes scanned by the given number of bytes.

Used by <KeyValueCursor as Cursor<KeyValue>>::next.

Trait Implementations

impl Debug for LimitManager

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

Formats the value using the given formatter.