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test26.cxx
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test26.cxx
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#include <functional>
#include <iostream>
#include <map>
#include "test_helpers.hxx"
using namespace pqxx;
// Example program for libpqxx. Modify the database, retaining transactional
// integrity using the transactor framework.
namespace
{
// Convert year to 4-digit format.
int To4Digits(int Y)
{
int Result = Y;
PQXX_CHECK(Y >= 0, "Negative year: " + to_string(Y));
if (Y < 70)
Result += 2000;
else if (Y < 100)
Result += 1900;
else
PQXX_CHECK(Y >= 1970, "Unexpected year: " + to_string(Y));
return Result;
}
// Transaction definition for year-field update. Returns conversions done.
std::map<int, int> update_years(connection_base &C)
{
std::map<int, int> conversions;
work tx{C};
// First select all different years occurring in the table.
result R{tx.exec("SELECT year FROM pqxxevents")};
// Note all different years currently occurring in the table, writing them
// and their correct mappings to m_conversions
for (const auto &r : R)
{
int Y{};
// Read year, and if it is non-null, note its converted value
if (r[0].to(Y))
conversions[Y] = To4Digits(Y);
}
// For each occurring year, write converted date back to whereever it may
// occur in the table. Since we're in a transaction, any changes made by
// others at the same time will not affect us.
for (const auto &c : conversions)
tx.exec0(
"UPDATE pqxxevents "
"SET year=" +
to_string(c.second) +
" "
"WHERE year=" +
to_string(c.first));
tx.commit();
return conversions;
}
void test_026()
{
connection conn;
{
nontransaction tx{conn};
test::create_pqxxevents(tx);
tx.commit();
}
// Perform (an instantiation of) the UpdateYears transactor we've defined
// in the code above. This is where the work gets done.
const auto conversions = perform(std::bind(update_years, std::ref(conn)));
PQXX_CHECK(not conversions.empty(), "No conversions done!");
}
PQXX_REGISTER_TEST(test_026);
} // namespace