pshampanier / libpqmxx

A PostgreSQL client library written in Modern C++

A simple PostgreSQL client library written in Modern C++.

libpqmxx is an unofficial C++ 11 client API for PostgreSQL.

The aim of this library is to provide an API very simple to use without any compromise on performances. Modern C++ features such as variadic templates are used to make the programing interface slick, very easy to use and the code to read.

• Automatic detection of the PostgresSQL datatype from C++ parameter's type:

  cnx.execute("SELECT from_date FROM titles WHERE emp_no=$1", 10020);

  Because 10020 is an int in C++, the library will bind this parameter to a PostgreSQL integer.

• One single method to get a column value from a row independently of the data type:

  int32_t emp_no = row.as<int32_t>(0);
  std::string title = row.as<std::string>(1);

• Supports of PostgreSQL arrays:

  auto array = cnx.execute("SELECT ARRAY['hello', 'world']").asArray<std::string>(0);
  std::string hello = array[0];
  std::string world = array[1];

• Use of the range-based for statement to iterate through the result.

  auto &employees = cnx.execute("SELECT emp_no, first_name || ' ' || last_name FROM employees");
  for (auto &employee: employees) {
    std::cout << row.as<int32_t>(0) << row.as<std::string>(1) << std::endl;
  }

• Results with only one row can be accessed directly without using the iterator:

  auto &employee = cnx.execute("SELECT last_name FROM employees WHERE emp_no=$1", 10001);
  std::cout << employee.as<std::string>(0) << std::endl;

• nullptr can be used to set a null value.

  cnx.execute("INSERT INTO titles VALUES ($1, $2, $3::date, $4)",
              10020, "Technique Leader", "1988-02-10", nullptr);

The online API documentation is available on gitbook.
If you are looking for the official C++ client library fro PostgreSQL, please visit pqxx.org.

Example

#include "postgres-connection.h"
#include "postgres-exceptions.h"

#include <iostream>

using namespace db::postgres;

int main() {

  Connection cnx;
  try {
    cnx.connect("postgresql://ci-test@localhost");

    cnx.execute(R"SQL(

      DROP TABLE IF EXISTS employees;

      CREATE TABLE employees (
        emp_no      INTEGER         NOT NULL,
        birth_date  DATE            NOT NULL,
        first_name  VARCHAR(14)     NOT NULL,
        last_name   VARCHAR(16)     NOT NULL,
        gender      "char"          NOT NULL,
        hire_date   DATE            NOT NULL,
        PRIMARY KEY (emp_no)
      );

    )SQL");

    std::cout << "Table created." << std::endl;

    int employees = cnx.execute(R"SQL(

      INSERT INTO employees VALUES
        (10001,'1973-09-02','Georgi','Facello','M','2006-06-26'),
        (10002,'1984-06-02','Bezalel','Simmel','F','2005-11-21'),
        (10003,'1979-12-03','Parto','Bamford','M','2006-08-28'),
        (10004,'1974-05-01','Chirstian','Koblick','M','2006-12-01'),
        (10005,'1975-01-21','Kyoichi','Maliniak','M','2009-09-12'),
        (10006,'1973-04-20','Anneke','Preusig','F','2009-06-02'),
        (10007,'1977-05-23','Tzvetan','Zielinski','F','2009-02-10'),
        (10008,'1978-02-19','Saniya','Kalloufi','M','2014-09-15'),
        (10009,'1972-04-19','Sumant','Peac','F','2005-02-18'),
        (10010,'1983-06-01','Duangkaew','Piveteau','F','2009-08-24'),
        (10011,'1973-11-07','Mary','Sluis','F','2010-01-22'),
        (10012,'1980-10-04','Patricio','Bridgland','M','2012-12-18'),
        (10013,'1983-06-07','Eberhardt','Terkki','M','2005-10-20'),
        (10014,'1976-02-12','Berni','Genin','M','2007-03-11'),
        (10015,'1979-08-19','Guoxiang','Nooteboom','M','2007-07-02'),
        (10016,'1981-05-02','Kazuhito','Cappelletti','M','2015-01-27'),
        (10017,'1978-07-06','Cristinel','Bouloucos','F','2013-08-03'),
        (10018,'1984-06-19','Kazuhide','Peha','F','2007-04-03'),
        (10019,'1973-01-23','Lillian','Haddadi','M','2016-04-30'),
        (10020,'1972-12-24','Mayuko','Warwick','M','2011-01-26')

    )SQL").count();

    std::cout << employees << " have been added." << std::endl;

    std::cout << "The three oldest employees are: " << std::endl;

    auto &oldest = cnx.execute(R"SQL(

      SELECT first_name, last_name, DATE_PART('year', now()) - DATE_PART('year', birth_date)
        FROM employees
       ORDER BY birth_date
       LIMIT 3

    )SQL");

    for (auto &row: oldest) {
      std::cout << "- " << row.as<std::string>(0) << " " << row.as<std::string>(1)
        << ", " << row.as<double>(2) << " years old." << std::endl;
    }

    auto &employee = cnx.execute(R"SQL(

      SELECT first_name, last_name, DATE_PART('year', birth_date)
        FROM employees WHERE birth_date = $1::date

    )SQL", "1973-11-07");

    std::cout << employee.as<std::string>(0) << " "
      << employee.as<std::string>(1) << " is born in "
      << employee.as<double>(2) << std::endl;

    int deleted = cnx.execute(R"SQL(

      DELETE FROM employees
        WHERE DATE_PART('year', birth_date) = $1 AND gender = $2

    )SQL", 1973, 'M').count();

    std::cout << deleted << " employees records have been deleted." << std::endl;

    return 0;
  }
  catch (ConnectionException e) {
    std::cerr << "Oops... Cannot connect...";
  }
  catch (ExecutionException e) {
    std::cerr << "Oops... " << e.what();
  }

  return -1;
}

Table created.
20 have been added.
The three oldest employees are: 
- Sumant Peac, 44 years old.
- Mayuko Warwick, 44 years old.
- Lillian Haddadi, 43 years old.
Mary Sluis is born in 1973
2 employees records have been deleted.

Usage

Using cmake.

cmake_minimum_required (VERSION 3.5)
project (myproject)

# C++ standard 11 minimum is required
set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED on)

# Configure libpq
find_package(PostgreSQL REQUIRED)
include_directories(${PostgreSQL_INCLUDE_DIRS})
link_directories(${PostgreSQL_LIBRARY_DIRS})

# Configure libpqmxx
include("../libpqmxx/libpqmxx.cmake")
include_directories(${LIBPQMXX_INCLUDE_DIRS})

# Configure your project
file(GLOB PROJECT_FILES ${CMAKE_CURRENT_LIST_DIR}/src/*.cpp)
add_executable(myproject ${PROJECT_FILES})
target_link_libraries(myproject ${LIBPQMXX_LIBRARIES} ${PostgreSQL_LIBRARIES})

Compatibility

• Linux x86_64 gcc 4.9, gcc 5, clang 3.6, clang 3.7.
• Mac x86_64 XCode 7.x
• Windows x86_64 Visual Studio 2015 Update 2

License

MIT

libpqmxx's Issues

Re-using a Result::iterator

How can I re-use a Result::iterator e.g. to iterate twice over a result set?

It doesn't seem to behave like a normal std iterator and it's also non-copyable due to the deleted assignment operator...

can this project surpport header only?

when i use libpqmxx, i have to reference the cpp file into my project, it is not convenient, so i hope the project surpport header only.

how to build in vs2015?

i want to use your libray, howerver i can't find the vs2015 project.

does not surpport int/float/double array.

hi, i can't find the method which is used to get int/float/double array, could you surpport array?

can't compile on linux

I try to compile on ubuntu14.04, error occur, thi is the message:
CMake Error at /usr/share/cmake-3.2/Modules/FindPackageHandleStandardArgs.cmake:138 (message):
Could NOT find PostgreSQL (missing: PostgreSQL_TYPE_INCLUDE_DIR) (found
version "9.3.13")
Call Stack (most recent call first):
/usr/share/cmake-3.2/Modules/FindPackageHandleStandardArgs.cmake:374 (_FPHSA_FAILURE_MESSAGE)
/usr/share/cmake-3.2/Modules/FindPostgreSQL.cmake:169 (find_package_handle_standard_args)
CMakeLists.txt:11 (find_package)

range-base for loop can't contain another execute operation.

when i use range-base for loop and sub, the assert happend. this is the pseudocode：

auto& res = cnx.execute("select * from xxx");
for(auto& row : res)
{
......
auto res1 = cnx.execute("select * from yyy"); //assert error
}

you konw this situation is very common, hope you resolve the problem, thanks.

How do I get the number of results returned by SELECT query?

It seems that .count() returns 0 for SELECT queries. So how do I get the number of results returned without iterating over every result?

It seems the Result::iterator also doesn't support std::distance