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
10020is anintin C++, the library will bind this parameter to a PostgreSQLinteger.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;nullptrcan 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_64gcc 4.9, gcc 5, clang 3.6, clang 3.7.Mac x86_64XCode 7.xWindows x86_64Visual Studio 2015 Update 2