Began designing the iterator

include/sqlgen/postgres/Iterator.hpp

@@ -1,8 +1,9 @@
 #ifndef SQLGEN_POSTGRES_ITERATOR_HPP_
 #define SQLGEN_POSTGRES_ITERATOR_HPP_
 
-#include <sqlite3.h>
+#include <libpq-fe.h>
 
+#include <memory>
 #include <optional>
 #include <string>
 #include <vector>
@@ -15,8 +16,14 @@
 namespace sqlgen::postgres {
 
 class Iterator : public sqlgen::IteratorBase {
+  using ConnPtr = Ref<PGconn>;
+
  public:
-  Iterator();
+  Iterator(const std::string& _sql, const ConnPtr& _conn);
+
+  Iterator(const Iterator& _other) = delete;
+
+  Iterator(Iterator&& _other) noexcept;
 
   ~Iterator();
 
@@ -29,7 +36,26 @@ class Iterator : public sqlgen::IteratorBase {
   Result<std::vector<std::vector<std::optional<std::string>>>> next(
       const size_t _batch_size) final;
 
+  Iterator& operator=(const Iterator& _other) = delete;
+
+  Iterator& operator=(Iterator&& _other) noexcept;
+
  private:
+  static std::string make_cursor_name() {
+    // TODO: Create unique cursor names.
+    return "sqlgen_cursor";
+  }
+
+ private:
+  /// A unique name to identify the cursor.
+  std::string cursor_name_;
+
+  /// The underlying postgres connection. We have this in here to prevent its
+  /// destruction for the lifetime of the iterator.
+  ConnPtr conn_;
+
+  /// Indicates that the iterator has been moved
+  bool moved_;
 };
 
 }  // namespace sqlgen::postgres

src/sqlgen/postgres/Iterator.cpp

@@ -6,13 +6,29 @@
 
 #include "sqlgen/internal/collect/vector.hpp"
 #include "sqlgen/internal/strings/strings.hpp"
-#include "sqlgen/sqlite/Iterator.hpp"
+#include "sqlgen/postgres/exec.hpp"
 
 namespace sqlgen::postgres {
 
-Iterator::Iterator() {}
+Iterator::Iterator(const std::string& _sql, const ConnPtr& _conn)
+    : cursor_name_(make_cursor_name()), conn_(_conn), moved_(false) {
+  exec(conn_, "BEGIN").value();
+  exec(conn_, "DECLARE " + cursor_name_ + " CURSOR FOR " + _sql).value();
+}
 
-Iterator::~Iterator() = default;
+Iterator::Iterator(Iterator&& _other) noexcept
+    : cursor_name_(std::move(_other.cursor_name_)),
+      conn_(std::move(_other.conn_)),
+      moved_(_other.moved_) {
+  _other.moved_ = true;
+}
+
+Iterator::~Iterator() {
+  if (!moved_) {
+    exec(conn_, "CLOSE " + cursor_name_);
+    exec(conn_, "END");
+  }
+}
 
 bool Iterator::end() const { return true; }
 
@@ -25,4 +41,15 @@ Result<std::vector<std::vector<std::optional<std::string>>>> Iterator::next(
   return error("TODO");
 }
 
+Iterator& Iterator::operator=(Iterator&& _other) noexcept {
+  if (this == &_other) {
+    return *this;
+  }
+  cursor_name_ = _other.cursor_name_;
+  conn_ = _other.conn_;
+  moved_ = _other.moved_;
+  _other.moved_ = true;
+  return *this;
+}
+
 }  // namespace sqlgen::postgres