What the rdbms layer of CTA does
The rdbms layer of CTA wraps the APIs of different relational database clients
in order to hide their syntactic differences from the rest of the CTA code base.
The rdbms library currently wraps the client APIs of the following 3 different
database management systems:
- Oracle
- PostgreSQL
- SQLite
An example of the using the rdbms layer of CTA
One of the best ways to explain how to use the rdbms library is to give an
example. The following code create a database table named TEST, inserts 2
rows into it and then queries the result:
using namespace cta;
const auto login = rdbms::Login::parseString("in_memory");
const uint64_t maxNbConns = 1;
rdbms::ConnPool connPool(login, maxNbConns);
auto conn = connPool.getConn();
{
const std::string sql = "CREATE TABLE TEST(ID INTEGER, VALUE VARCHAR(80))";
auto stmt = conn.createStmt(sql);
stmt.executeNonQuery();
}
{
const uint64_t id = 1;
const std::string value = "ONE";
const std::string sql = "INSERT INTO TEST(ID, VALUE) VALUES (:ID, :VALUE);";
auto stmt = conn.createStmt(sql);
stmt.bindUint64(":ID", id);
stmt.bindString(":VALUE", value);
stmt.executeNonQuery();
}
{
const uint64_t id = 2;
const std::string value = "TWO";
const std::string sql = "INSERT INTO TEST(ID, VALUE) VALUES (:ID, :VALUE);";
auto stmt = conn.createStmt(sql);
stmt.bindUint64(":ID", id);
stmt.bindString(":VALUE", value);
stmt.executeNonQuery();
}
{
const std::string sql = "SELECT TEST.ID AS ID, TEST.VALUE AS VALUE FROM TEST ORDER BY ID";
auto stmt = conn.createStmt(sql);
auto rset = stmt.executeQuery();
while (rset.next()) {
std::cout << "ID=" << rset.columnUint64("ID") << " VALUE='" << rset.columnString("VALUE") << "'" << std::endl;
}
}The following class diagram shows the most important design details of the rdbms layer:
