feat: docstore package created

internal/docstore/compaction.go

@@ -0,0 +1,64 @@
+// Copyright 2018-2020 Burak Sezer
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package storage
+
+import (
+	"log"
+)
+
+func (d *Docstore) CompactTables() bool {
+	if len(d.tables) == 1 {
+		return true
+	}
+
+	var total int
+	fresh := d.tables[len(d.tables)-1]
+	for _, old := range d.tables[:len(d.tables)-1] {
+		// Removing keys while iterating on map is totally safe in Go.
+		for hkey := range old.hkeys {
+			entry, _ := old.getRaw(hkey)
+			err := fresh.putRaw(hkey, entry)
+			if err == errNotEnoughSpace {
+				// Create a new table and put the new k/v pair in it.
+				nt := newTable(d.Inuse() * 2)
+				d.tables = append(d.tables, nt)
+				return false
+			}
+			if err != nil {
+				log.Printf("[ERROR] Failed to compact tables. HKey: %d: %v", hkey, err)
+			}
+
+			// Dont check the returned val, it'd useless because
+			// we are sure that the key is already there.
+			old.delete(hkey)
+			total++
+			if total > 1000 {
+				// It'd enough. Don't block the instance.
+				return false
+			}
+		}
+	}
+
+	// Remove empty tables. Keep the last table.
+	tmp := []*table{d.tables[len(d.tables)-1]}
+	for _, t := range d.tables[:len(d.tables)-1] {
+		if len(t.hkeys) == 0 {
+			continue
+		}
+		tmp = append(tmp, t)
+	}
+	d.tables = tmp
+	return true
+}