sstable interface for committed data (#971)

forest/sstable/sstable.go

@@ -0,0 +1,46 @@
+package sstable
+
+import (
+	"github.com/treeverse/lakefs/catalog/rocks"
+)
+
+// SSTableID is an identifier for an SSTable
+type SSTableID string
+
+type Manager interface {
+	// GetEntry returns the entry matching the path in the SSTable referenced by the id.
+	// If path not found, (nil, ErrPathNotFound) is returned.
+	GetEntry(path rocks.Path, tid SSTableID) (*rocks.Entry, error)
+
+	// NewSSTableIterator takes a given SSTable and returns an EntryIterator seeked to >= "from" path
+	NewSSTableIterator(tid SSTableID, from rocks.Path) (rocks.EntryIterator, error)
+
+	// GetWriter returns a new SSTable writer instance
+	GetWriter() (Writer, error)
+}
+
+// WriteResult is the result of a completed write of an SSTable
+type WriteResult struct {
+	// SSTableID is the identifier for the written SSTable.
+	// Calculated by an hash function to all paths and entries.
+	SSTableID SSTableID
+
+	// First is the Path of the first entry in the SSTable.
+	First rocks.Path
+
+	// Last is the Path of the last entry in the SSTable.
+	Last rocks.Path
+
+	// Count is the number of entries in the SSTable.
+	Count int
+}
+
+// Writer is an abstraction for writing SSTables.
+// Written entries must be sorted by path.
+type Writer interface {
+	// WriteEntry appends the given entry to the SSTable
+	WriteEntry(path rocks.Path, entry rocks.Entry) error
+
+	// Close flushes all entries to the disk and returns the WriteResult.
+	Close() (*WriteResult, error)
+}