Add postgresql support

src/database/postgresql_engine.cpp

@@ -0,0 +1,77 @@
+#include <database/postgresql_engine.hpp>
+
+#include <database/postgresql_statement.hpp>
+
+#include <logger/logger.hpp>
+
+PostgresqlEngine::PostgresqlEngine(PGconn*const conn):
+    conn(conn)
+{}
+
+PostgresqlEngine::~PostgresqlEngine()
+{
+  PQfinish(this->conn);
+}
+
+std::unique_ptr<DatabaseEngine> PostgresqlEngine::open(const std::string& conninfo)
+{
+  log_debug("trying to open: ", conninfo);
+  PGconn* con = PQconnectdb(conninfo.data());
+
+  if (!con)
+    {
+      log_error("Failed to allocate a Postgresql connection");
+      throw std::runtime_error("");
+    }
+  const auto status = PQstatus(con);
+  if (status != CONNECTION_OK)
+    {
+      const char* errmsg = PQerrorMessage(con);
+      log_error("Postgresql connection failed: ", errmsg);
+      throw std::runtime_error("failed to open connection.");
+    }
+  return std::make_unique<PostgresqlEngine>(con);
+}
+
+std::set<std::string> PostgresqlEngine::get_all_columns_from_table(const std::string& table_name)
+{
+  const auto query = "SELECT column_name from information_schema.columns where table_name='" + table_name + "'";
+  auto statement = this->prepare(query);
+  std::set<std::string> columns;
+
+  while (statement->step() == StepResult::Row)
+    columns.insert(statement->get_column_text(0));
+
+  log_debug("found ", columns.size(), " columns.");
+  return columns;
+}
+
+std::tuple<bool, std::string> PostgresqlEngine::raw_exec(const std::string& query)
+{
+  log_debug("raw_exec:", query);
+  PGresult* res = PQexec(this->conn, query.data());
+  auto res_status = PQresultStatus(res);
+  if (res_status != PGRES_COMMAND_OK)
+    return std::make_tuple(false, PQresultErrorMessage(res));
+  return std::make_tuple(true, std::string{});
+}
+
+std::unique_ptr<Statement> PostgresqlEngine::prepare(const std::string& query)
+{
+  return std::make_unique<PostgresqlStatement>(query, this->conn);
+}
+
+void PostgresqlEngine::extract_last_insert_rowid(Statement& statement)
+{
+  this->last_inserted_rowid = statement.get_column_int64(0);
+}
+
+std::string PostgresqlEngine::get_returning_id_sql_string(const std::string& col_name)
+{
+  return " RETURNING " + col_name;
+}
+
+std::string PostgresqlEngine::id_column_type()
+{
+  return "SERIAL";
+}