LibSQL: Ungracefully handle database version incompatibilities

In the long run, this is obviously a bad way to handle version changes
to the SQL database files. We will want to migrate old databases to new
formats. Until we figure out a good way to do that, wipe old databases
so that we don't crash trying to read incompatible data.

Author: trflynn89

Tests/LibSQL/TestSqlDatabase.cpp

@@ -110,7 +110,7 @@ TEST_CASE(create_heap)
     ScopeGuard guard([]() { unlink("/tmp/test.db"); });
     auto heap = SQL::Heap::construct("/tmp/test.db");
     EXPECT(!heap->open().is_error());
-    EXPECT_EQ(heap->version(), 0x00000001u);
+    EXPECT_EQ(heap->version(), SQL::Heap::current_version);
 }
 
 TEST_CASE(create_from_dev_random)

Userland/Libraries/LibSQL/Heap.cpp

@@ -8,6 +8,7 @@
 #include <AK/Format.h>
 #include <AK/QuickSort.h>
 #include <LibCore/IODevice.h>
+#include <LibCore/System.h>
 #include <LibSQL/Heap.h>
 #include <LibSQL/Serializer.h>
 #include <sys/stat.h>
@@ -58,6 +59,15 @@ ErrorOr<void> Heap::open()
         initialize_zero_block();
     }
 
+    // FIXME: We should more gracefully handle version incompatibilities. For now, we drop the database.
+    if (m_version != current_version) {
+        dbgln_if(SQL_DEBUG, "Heap file {} opened has incompatible version {}. Deleting for version {}.", name(), m_version, current_version);
+        m_file = nullptr;
+
+        TRY(Core::System::unlink(name()));
+        return open();
+    }
+
     dbgln_if(SQL_DEBUG, "Heap file {} opened. Size = {}", name(), size());
     return {};
 }
@@ -248,7 +258,7 @@ void Heap::update_zero_block()
 
 void Heap::initialize_zero_block()
 {
-    m_version = 0x00000001;
+    m_version = current_version;
     m_schemas_root = 0;
     m_tables_root = 0;
     m_table_columns_root = 0;

Userland/Libraries/LibSQL/Heap.h

@@ -33,6 +33,8 @@ class Heap : public Core::Object {
     C_OBJECT(Heap);
 
 public:
+    static constexpr inline u32 current_version = 1;
+
     virtual ~Heap() override;
 
     ErrorOr<void> open();
@@ -104,7 +106,7 @@ class Heap : public Core::Object {
     u32 m_schemas_root { 0 };
     u32 m_tables_root { 0 };
     u32 m_table_columns_root { 0 };
-    u32 m_version { 0x00000001 };
+    u32 m_version { current_version };
     Array<u32, 16> m_user_values { 0 };
     HashMap<u32, ByteBuffer> m_write_ahead_log;
 };