added postgres backend

backends/postgres/include/postgres_connection.hpp

@@ -0,0 +1,51 @@
+#ifndef QUERY_POSTGRES_CONNECTION_HPP
+#define QUERY_POSTGRES_CONNECTION_HPP
+
+#ifdef _MSC_VER
+#ifdef matador_postgres_EXPORTS
+#define MATADOR_POSTGRES_API __declspec(dllexport)
+#else
+#define MATADOR_POSTGRES_API __declspec(dllimport)
+#endif
+#pragma warning(disable: 4355)
+#else
+#define MATADOR_POSTGRES_API
+#endif
+
+#include "matador/sql/connection_impl.hpp"
+
+#include <libpq-fe.h>
+
+namespace matador::backends::postgres {
+
+class postgres_connection : public matador::sql::connection_impl
+{
+public:
+  explicit postgres_connection(const sql::connection_info &info);
+  void open() override;
+  void close() override;
+  bool is_open() override;
+
+  std::unique_ptr<sql::query_result_impl> fetch(const std::string &stmt) override;
+  void prepare(const std::string &stmt) override;
+
+  size_t execute(const std::string &stmt) override;
+
+  sql::record describe(const std::string& table) override;
+
+  bool exists(const std::string &table_name) override;
+
+private:
+  PGconn *conn_{nullptr};
+};
+
+}
+
+extern "C"
+{
+MATADOR_POSTGRES_API matador::sql::connection_impl* create_database(const matador::sql::connection_info &info);
+
+MATADOR_POSTGRES_API void destroy_database(matador::sql::connection_impl *db);
+}
+
+#endif //QUERY_POSTGRES_CONNECTION_HPP

backends/postgres/include/postgres_dialect.hpp

@@ -0,0 +1,19 @@
+#ifndef QUERY_POSTGRES_DIALECT_HPP
+#define QUERY_POSTGRES_DIALECT_HPP
+
+#ifdef _MSC_VER
+#ifdef matador_postgres_EXPORTS
+#define MATADOR_POSTGRES_API __declspec(dllexport)
+#else
+#define MATADOR_POSTGRES_API __declspec(dllimport)
+#endif
+#pragma warning(disable: 4355)
+#else
+#define MATADOR_POSTGRES_API
+#endif
+
+#include "matador/sql/dialect.hpp"
+
+extern "C" [[maybe_unused]] MATADOR_POSTGRES_API const matador::sql::dialect* get_dialect();
+
+#endif //QUERY_POSTGRES_DIALECT_HPP

backends/postgres/include/postgres_error.hpp

@@ -0,0 +1,16 @@
+#ifndef QUERY_POSTGRES_ERROR_HPP
+#define QUERY_POSTGRES_ERROR_HPP
+
+#include <libpq-fe.h>
+
+#include <string>
+
+namespace matador::backends::postgres {
+
+void throw_postgres_error(const char *what, const std::string &source);
+void throw_postgres_error(PGconn *db, const std::string &source);
+void throw_postgres_error(PGresult *res, PGconn *db, const std::string &source, const std::string &sql);
+
+}
+
+#endif //QUERY_POSTGRES_ERROR_HPP

backends/postgres/include/postgres_result_reader.hpp

@@ -0,0 +1,47 @@
+#ifndef QUERY_POSTGRES_RESULT_READER_HPP
+#define QUERY_POSTGRES_RESULT_READER_HPP
+
+#include <libpq-fe.h>
+#include "matador/sql/query_result_reader.hpp"
+
+namespace matador::backends::postgres {
+
+class postgres_result_reader : public sql::query_result_reader
+{
+public:
+  explicit postgres_result_reader(PGresult *result);
+  ~postgres_result_reader() override;
+
+  [[nodiscard]] size_t column_count() const override;
+  [[nodiscard]] const char *column(size_t index) const override;
+  bool fetch() override;
+
+  void read_value(const char *id, size_t index, char &value) override;
+  void read_value(const char *id, size_t index, short &value) override;
+  void read_value(const char *id, size_t index, int &value) override;
+  void read_value(const char *id, size_t index, long &value) override;
+  void read_value(const char *id, size_t index, long long int &value) override;
+  void read_value(const char *id, size_t index, unsigned char &value) override;
+  void read_value(const char *id, size_t index, unsigned short &value) override;
+  void read_value(const char *id, size_t index, unsigned int &value) override;
+  void read_value(const char *id, size_t index, unsigned long &value) override;
+  void read_value(const char *id, size_t index, unsigned long long int &value) override;
+  void read_value(const char *id, size_t index, bool &value) override;
+  void read_value(const char *id, size_t index, float &value) override;
+  void read_value(const char *id, size_t index, double &value) override;
+  void read_value(const char *id, size_t index, char *value, size_t s) override;
+  void read_value(const char *id, size_t index, std::string &value) override;
+  void read_value(const char *id, size_t index, std::string &value, size_t s) override;
+  void read_value(const char *id, size_t index, sql::any_type &value, sql::data_type_t type, size_t size) override;
+
+private:
+  PGresult *result_{};
+
+  size_t row_count_{};
+  size_t column_count_{};
+  size_t row_index_{0};
+};
+
+}
+
+#endif //QUERY_POSTGRES_RESULT_READER_HPP