Implement an in-memory databasewqa

pkg/ramdb/ram.go

@@ -0,0 +1,43 @@
+package ramdb
+
+type database struct {
+	tables map[string]*table
+}
+
+// NewDatabase initializes a new database with no tables.
+func NewDatabase() *database {
+	return &database{
+		tables: make(map[string]*table),
+	}
+}
+
+// From selects a table for running commands.
+func (db *database) From(tablename string) *table {
+	t, ok := db.tables[tablename]
+	if !ok {
+		return &table{}
+	}
+
+	return t
+}
+
+// CreateTable creates a new table in the database with indexes for each column specified.
+func (db *database) CreateTable(tablename string, indexOnColumns ...string) error {
+	if _, found := db.tables[tablename]; found {
+		return ErrTableExists
+	}
+
+	tbl := &table{
+		exists: true,
+	}
+
+	for _, onColumn := range indexOnColumns {
+		err := tbl.CreateIndex(onColumn)
+		if err != nil {
+			return err
+		}
+	}
+
+	db.tables[tablename] = tbl
+	return nil
+}