Implement an in-memory databasewqa

pkg/ramdb/commands.go

@@ -0,0 +1,93 @@
+package ramdb
+
+import "github.com/google/btree"
+
+// Get validates that the table and index for the given column exists and searches for the given key in the tree.
+func (t *table) Get(column, key string) (r *record, err error) {
+	if !t.exists {
+		return nil, ErrNoTable
+	}
+
+	if !t.HasIndex(column) {
+		return nil, ErrNoIndex
+	}
+
+	return t.keyLookup(key, t.indexes[column])
+}
+
+// keyLookup tries to find the given key in the tree. It returns ErrNoRecord if not found.
+func (t *table) keyLookup(key string, index *index) (r *record, err error) {
+	item := &record{id: keyHash(key)}
+	result := index.tree.Get(item)
+	if result == nil {
+		return nil, ErrNoRecord
+	}
+
+	return result.(*record), nil
+}
+
+// Select returns all of the records in the database sorted in ascending order by id.
+func (t *table) Select(column string) (rr []*record, err error) {
+	if !t.exists {
+		return nil, ErrNoTable
+	}
+
+	if !t.HasIndex(column) {
+		return nil, ErrNoIndex
+	}
+
+	t.indexes[column].tree.Ascend(func(item btree.Item) bool {
+		r := item.(*record)
+		rr = append(rr, r)
+		return true
+	})
+
+	return
+}
+
+// Insert adds the record to the database. It returns ErrRecordExists if the record already exists. Insert is thread safe.
+func (t *table) Insert(r *record) error {
+	if !t.exists {
+		return ErrNoTable
+	}
+
+	if !t.HasIndex(r.keyColumn) {
+		return ErrNoIndex
+	}
+
+	index := t.indexes[r.keyColumn]
+
+	if has := index.tree.Has(r); has {
+		return ErrRecordExists
+	}
+
+	t.mutex.Lock()
+	defer t.mutex.Unlock()
+
+	index.tree.ReplaceOrInsert(r)
+	return nil
+
+}
+
+// Delete removes the item from the database. It returns ErrNoRecord if the record does not exist and ErrNotDeleted if the removal fails. Delete is thread safe.
+func (t *table) Delete(r *record) error {
+	if !t.exists {
+		return ErrNoTable
+	}
+
+	if !t.HasIndex(r.keyColumn) {
+		return ErrNoIndex
+	}
+
+	index := t.indexes[r.keyColumn]
+
+	if has := index.tree.Has(r); !has {
+		return ErrNoRecord
+	}
+
+	t.mutex.Lock()
+	defer t.mutex.Unlock()
+
+	index.tree.Delete(r)
+	return nil
+}