First Commit

ext/libpqxx-7.7.3/test/test26.cxx

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+#include <iostream>
+#include <map>
+
+#include <pqxx/nontransaction>
+#include <pqxx/transaction>
+#include <pqxx/transactor>
+
+#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 &C)
+{
+  std::map<int, int> conversions;
+  work tx{C};
+
+  // Note all different years currently occurring in the table, writing them
+  // and their correct mappings to m_conversions
+  for (auto const &[y] :
+       tx.stream<std::optional<int>>("SELECT year FROM pqxxevents"))
+  {
+    // Read year, and if it is non-null, note its converted value
+    if (bool(y))
+      conversions[y.value()] = To4Digits(y.value());
+  }
+
+  // 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 (auto const &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.
+  auto const conversions{perform([&conn] { return update_years(conn); })};
+
+  PQXX_CHECK(not std::empty(conversions), "No conversions done!");
+}
+
+
+PQXX_REGISTER_TEST(test_026);
+} // namespace