Struct segment

segment.go:100–134

A segment is a basic implementation of the segment related interfaces and represents a sequence of key-val entries or operations. A segment's kvs will be sorted by key when the segment is pushed into the collection. A segment implements the Batch interface.

// is pushed into the collection.  A segment implements the Batch
// interface.
type segment struct {
	// Each key-val operation is encoded as 2 uint64's...
	// - operation (see: maskOperation) |
	//       key length (see: maskKeyLength) |
	//       val length (see: maskValLength).
	// - start index into buf for key-val bytes.
	kvs []uint64

	// Contiguous backing memory for the keys and vals of the segment.
	buf []byte

	// If this segment needs sorting, then needSorterCh will be
	// non-nil and also the first goroutine that reads successfully
	// from needSorterCh becomes the sorter of this segment.  All
	// other goroutines must instead wait on the waitSortedCh.
	needSorterCh chan bool

	// Once the sorter of this segment is done sorting the kvs, it
	// close()'s the waitSortedCh, treating waitSortedCh like a
	// one-way latch.  The needSorterCh and waitSortedCh will either
	// be nil or non-nil together.  A segment that was "born
	// sorted" will have needSorterCh and waitSortedCh as both nil.
	waitSortedCh chan struct{}

	totOperationSet   uint64
	totOperationDel   uint64
	totOperationMerge uint64
	totKeyByte        uint64
	totValByte        uint64

	rootCollection *collection // Non-nil when segment is from a batch.

	// In-memory index, immutable after segment initialization.
	index *segmentKeysIndex
}

// See the OperationXxx consts.
const maskOperation = uint64(0x0F00000000000000)