sqlite backend with actual pagination

1 files changed, 60 insertions, 0 deletions

diff --git a/include/SqliteBackend.h b/include/SqliteBackend.h
new file mode 100644
index 0000000..0b21925
--- /dev/null
+++ b/include/SqliteBackend.h
@@ -0,0 +1,60 @@
+#pragma once
+
+#include "Api.h"
+#include "IStorageBackend.h"
+
+#include <sqlite3.h>
+#include <string>
+#include <vector>
+
+/**
+ * @file SqliteBackend.h
+ * @brief IStorageBackend implementation backed by an in-process SQLite database.
+ *
+ * SQLite schema:
+ *
+ *   kv(hash TEXT PRIMARY KEY, value BLOB NOT NULL)
+ *     — content-addressed store; key is the SHA256 hex digest of value.
+ *
+ *   relation_index(path TEXT NOT NULL, tuple_hash TEXT NOT NULL,
+ *                  UNIQUE(path, tuple_hash))
+ *     — maps a relation's logical path to the ordered set of tuple hashes
+ *       it contains. Corresponds to Sakura's per-relation B+ tree of
+ *       tuple hashes stored in the physical layer.
+ */
+
+namespace nt
+{
+    /**
+     * @class SqliteBackend
+     * @brief IStorageBackend that persists data in a SQLite database.
+     *
+     * Constructed with a file path or ":memory:" for an in-process database.
+     * All KV values are opaque blobs; callers are responsible for serialization
+     * (see TupleCodec).
+     */
+    class NT_API SqliteBackend : public IStorageBackend
+    {
+    public:
+        /**
+         * @brief Opens (or creates) a SQLite database at @p path.
+         * @param path File path, or ":memory:" for an in-process database.
+         * @throws std::runtime_error if the database cannot be opened.
+         */
+        explicit SqliteBackend(const std::string& path = ":memory:");
+        ~SqliteBackend() override;
+
+        std::string Put(std::vector<uint8_t> value) override;
+        std::optional<std::vector<uint8_t>> Get(const std::string& hash) override;
+        void LinkTuple(const std::vector<std::string>& relation_path,
+                       const std::string& tuple_hash) override;
+        std::vector<std::string> TupleHashes(const std::vector<std::string>& relation_path,
+                                             std::size_t offset,
+                                             std::size_t limit) override;
+
+    private:
+        sqlite3* db_ = nullptr;
+
+        static std::string PathKey(const std::vector<std::string>& path);
+    };
+}