Optimize getting counts of transaction items

Previously during `history list` we separately fetched all transaction
packages, groups and environments only to count them. This could be
quite slow because it resulted in a lot of separate DB connections.

Now we fetch only the counts and use only one DB connection.

include/libdnf5/transaction/transaction_history.hpp

@@ -86,6 +86,14 @@ class LIBDNF_API TransactionHistory {
     TransactionItemReason transaction_item_reason_at(
         const std::string & name, const std::string & arch, int64_t transaction_id_point);
 
+    /// Get counts of transaction items for specified transactions.
+    /// It gets the counts in a single db query.
+    ///
+    /// @param transactions Get counts for these transactions.
+    ///
+    /// @return Mapped transaction id -> count.
+    std::unordered_map<int64_t, int64_t> get_transaction_item_counts(const std::vector<Transaction> & transactions);
+
 private:
     /// Create a new Transaction object.
     LIBDNF_LOCAL libdnf5::transaction::Transaction new_transaction();

libdnf5-cli/output/transactionlist.cpp

@@ -24,12 +24,20 @@ along with libdnf.  If not, see <https://www.gnu.org/licenses/>.
 
 #include "libdnf5-cli/tty.hpp"
 
+#include "libdnf5/transaction/transaction_history.hpp"
+
 #include <libsmartcols/libsmartcols.h>
 
 
 namespace libdnf5::cli::output {
 
 void print_transaction_list(std::vector<libdnf5::transaction::Transaction> & ts_list) {
+    std::unordered_map<int64_t, int64_t> id_to_item_count;
+    if (!ts_list.empty()) {
+        libdnf5::transaction::TransactionHistory history(ts_list[0].get_base());
+        id_to_item_count = history.get_transaction_item_counts(ts_list);
+    }
+
     std::unique_ptr<libscols_table, decltype(&scols_unref_table)> table(scols_new_table(), &scols_unref_table);
 
     scols_table_new_column(table.get(), "ID", 0, SCOLS_FL_RIGHT);
@@ -49,11 +57,7 @@ void print_transaction_list(std::vector<libdnf5::transaction::Transaction> & ts_
         scols_line_set_data(ln, 2, libdnf5::utils::string::format_epoch(ts.get_dt_start()).c_str());
         // TODO(lukash) fill the Actions(s), if we even want them?
         scols_line_set_data(ln, 3, "");
-        scols_line_set_data(
-            ln,
-            4,
-            std::to_string(ts.get_packages().size() + ts.get_comps_groups().size() + ts.get_comps_environments().size())
-                .c_str());
+        scols_line_set_data(ln, 4, std::to_string(id_to_item_count.at(ts.get_id())).c_str());
     }
 
     scols_print_table(table.get());

libdnf5/transaction/db/trans.cpp

@@ -256,4 +256,48 @@ TransactionItemReason TransactionDbUtils::transaction_item_reason_at(
     return TransactionItemReason::NONE;
 }
 
+static constexpr const char * ITEM_COUNT_SQL = R"**(
+    SELECT
+        "trans"."id",
+        COUNT("trans_item"."trans_id") AS "item_count"
+    FROM "trans"
+    LEFT JOIN "trans_item" ON "trans"."id" = "trans_item"."trans_id"
+)**";
+
+std::unordered_map<int64_t, int64_t> TransactionDbUtils::transactions_item_counts(
+    const BaseWeakPtr & base, const std::vector<Transaction> & transactions) {
+    auto conn = transaction_db_connect(*base);
+
+    std::string sql = ITEM_COUNT_SQL;
+
+    if (!transactions.empty()) {
+        sql += " WHERE \"trans\".\"id\" IN (";
+        for (size_t i = 0; i < transactions.size(); ++i) {
+            if (i == 0) {
+                sql += "?";
+            } else {
+                sql += ", ?";
+            }
+        }
+        sql += ")";
+    }
+
+    // GROUP BY has to be after WHERE clause
+    sql += "GROUP BY \"trans\".\"id\"";
+
+    auto query = libdnf5::utils::SQLite3::Query(*conn, sql);
+
+    for (size_t i = 0; i < transactions.size(); ++i) {
+        query.bind(static_cast<int>(i + 1), transactions[i].get_id());
+    }
+
+    std::unordered_map<int64_t, int64_t> id_to_count;
+
+    while (query.step() == libdnf5::utils::SQLite3::Statement::StepResult::ROW) {
+        id_to_count.emplace(query.get<int>("id"), query.get<int64_t>("item_count"));
+    }
+
+    return id_to_count;
+}
+
 }  // namespace libdnf5::transaction

libdnf5/transaction/db/trans.hpp

@@ -64,6 +64,10 @@ class TransactionDbUtils {
     /// Get reason for name-arch at a point in history specified by transaction id.
     static TransactionItemReason transaction_item_reason_at(
         const BaseWeakPtr & base, const std::string & name, const std::string & arch, int64_t transaction_id_point);
+
+    /// Get transaction item count for history transactions specified by transaction ids.
+    static std::unordered_map<int64_t, int64_t> transactions_item_counts(
+        const BaseWeakPtr & base, const std::vector<Transaction> & transactions);
 };
 
 }  // namespace libdnf5::transaction

libdnf5/transaction/transaction_history.cpp

@@ -80,4 +80,9 @@ TransactionItemReason TransactionHistory::transaction_item_reason_at(
     return TransactionDbUtils::transaction_item_reason_at(p_impl->base, name, arch, transaction_id_point);
 }
 
+std::unordered_map<int64_t, int64_t> TransactionHistory::get_transaction_item_counts(
+    const std::vector<Transaction> & transactions) {
+    return TransactionDbUtils::transactions_item_counts(p_impl->base, transactions);
+}
+
 }  // namespace libdnf5::transaction