LibSQL: Partially implement the DELETE command

This implements enough to delete rows filtered by a WHERE clause.

Userland/Libraries/LibSQL/AST/AST.h

@@ -1017,6 +1017,8 @@ public:
     RefPtr<Expression> const& where_clause() const { return m_where_clause; }
     RefPtr<ReturningClause> const& returning_clause() const { return m_returning_clause; }
 
+    virtual ResultOr<ResultSet> execute(ExecutionContext&) const override;
+
 private:
     RefPtr<CommonTableExpressionList> m_common_table_expression_list;
     NonnullRefPtr<QualifiedTableName> m_qualified_table_name;

Userland/Libraries/LibSQL/AST/Delete.cpp

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2022, Tim Flynn <trflynn89@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibSQL/AST/AST.h>
+#include <LibSQL/Database.h>
+#include <LibSQL/Meta.h>
+#include <LibSQL/Row.h>
+
+namespace SQL::AST {
+
+ResultOr<ResultSet> Delete::execute(ExecutionContext& context) const
+{
+    auto const& schema_name = m_qualified_table_name->schema_name();
+    auto const& table_name = m_qualified_table_name->table_name();
+    auto table_def = TRY(context.database->get_table(schema_name, table_name));
+
+    ResultSet result { SQLCommand::Delete };
+
+    for (auto& table_row : TRY(context.database->select_all(*table_def))) {
+        context.current_row = &table_row;
+
+        if (auto const& where_clause = this->where_clause()) {
+            auto where_result = TRY(where_clause->evaluate(context)).to_bool();
+            if (!where_result.has_value() || !where_result.value())
+                continue;
+        }
+
+        TRY(context.database->remove(table_row));
+
+        // FIXME: Implement the RETURNING clause.
+    }
+
+    return result;
+}
+
+}