From ec03bfbc84e9c3eca4532ee4498db90048aee8f3 Mon Sep 17 00:00:00 2001
From: Nathan Wallach <tani@technion.ac.il>
Date: Thu, 1 Dec 2022 17:49:15 +0200
Subject: [PATCH] Add code to allow adding multiple records to the problem_user
 table (for a single set for a single user) as a batch, which allows reducing
 the number of test calls made to the database. It would be better to be able
 to add all records in a single database call, but at present the underlying
 database abstraction layer does not seem to have any support for inserting
 multiple records in one call.

---
 lib/WeBWorK/ContentGenerator/Instructor.pm | 48 ++++++++++++++++++----
 lib/WeBWorK/DB.pm                          | 47 +++++++++++++++++++++
 2 files changed, 87 insertions(+), 8 deletions(-)

diff --git a/lib/WeBWorK/ContentGenerator/Instructor.pm b/lib/WeBWorK/ContentGenerator/Instructor.pm
index ca6bafb89b..40a964053d 100644
--- a/lib/WeBWorK/ContentGenerator/Instructor.pm
+++ b/lib/WeBWorK/ContentGenerator/Instructor.pm
@@ -75,10 +75,9 @@ sub assignSetToUser {
 	}
 
 	my @GlobalProblems = grep { defined $_ } $db->getAllGlobalProblems($setID);
-	foreach my $GlobalProblem (@GlobalProblems) {
-		my @result = $self->assignProblemToUser($userID, $GlobalProblem);
-		push @results, @result if @result and not $set_assigned;
-	}
+
+	my @result = $self->assignMultipleProblemsToUser($userID, @GlobalProblems);
+	push @results, @result if @result and not $set_assigned;
 
 	return @results;
 }
@@ -155,6 +154,41 @@ sub unassignSetFromUser {
 	$db->deleteUserSet($userID, $setID);
 }
 
+=item assignMultipleProblemsToUser($userID, @GlobalProblems)
+
+Assigns a list of problems to the given user.
+If some problem is already assigned to the user, an error string is returned.
+
+=cut
+
+sub assignMultipleProblemsToUser {
+	my ($self, $userID, @GlobalProblems) = @_;
+	my $db = $self->{db};
+
+	my $GlobalProblem;
+	my $UserProblem;
+	my @records;
+	foreach $GlobalProblem (@GlobalProblems) {
+		$UserProblem = $db->newUserProblem;
+		$UserProblem->user_id($userID);
+		$UserProblem->set_id($GlobalProblem->set_id);
+		$UserProblem->problem_id($GlobalProblem->problem_id);
+		initializeUserProblem($UserProblem, undef);    # No $seed
+		push(@records, $UserProblem);
+	}
+
+	eval { $db->addUserMultipleProblem(@records) };
+	if ($@) {
+		if ($@ =~ m/user problems existed/) {
+			return "some problem in the set " . $GlobalProblem->set_id . " were already assigned to user $userID.\n $@";
+		} else {
+			die $@;
+		}
+	}
+
+	return ();
+}
+
 =item assignProblemToUser($userID, $GlobalProblem, $seed)
 
 Assigns the given problem to the given user. If the problem is already assigned
@@ -338,10 +372,8 @@ sub assignSetToAllUsers {
 		debug("$setID: (done with that)");
 
 		debug("$setID: adding UserProblems for $userID");
-		foreach my $GlobalProblem (@GlobalProblems) {
-			my @result = $self->assignProblemToUser($userID, $GlobalProblem);
-			push @results, @result if @result;
-		}
+		my @result = $self->assignMultipleProblemsToUser($userID, @GlobalProblems);
+		push @results, @result if @result;
 		debug("$setID: (done with that)");
 	}
 
diff --git a/lib/WeBWorK/DB.pm b/lib/WeBWorK/DB.pm
index 0748010363..cd9ef28f88 100644
--- a/lib/WeBWorK/DB.pm
+++ b/lib/WeBWorK/DB.pm
@@ -2051,6 +2051,53 @@ sub addUserProblem {
 	}
 }
 
+# Adds multiple problems to a user with less database calls.
+sub addUserMultipleProblem {
+	# Intended to be used to add multiple problems to a SINGLE set with less DB calls.
+	# Not for use by versioned sets
+	my ($self, @ProblemList) = @_;
+
+	my $UserProblem = $ProblemList[0];
+
+	my ($nv_set_id, $versionNum) = grok_vsetID($UserProblem->set_id);
+	croak "addUserMultipleProblem does not support versioned sets"
+		if defined($versionNum);
+
+	# Possible improvement, if a version set was sent, make calls to addUserProblem for each one.
+
+	# Do a single checkArgs call, all records in the list were made in the same manner
+	my @tmp = ($UserProblem);
+	$self->checkArgs(\@tmp, qw/VREC:problem_user/);
+
+	# Just needed once
+	croak "addUserProblem: user set ", $UserProblem->set_id, " for user ", $UserProblem->user_id, " not found"
+		unless $self->{set_user}->exists($UserProblem->user_id, $UserProblem->set_id);
+
+	my @sawRecordExists;
+	my @otherErrors;
+	my @ToReturn;
+	my $result1;
+
+	foreach $UserProblem (@ProblemList) {
+		eval { $result1 = $self->{problem_user}->add($UserProblem); };
+		if (my $ex = caught WeBWorK::DB::Ex::RecordExists) {
+			push(@sawRecordExists, $UserProblem->problem_id);
+		} elsif ($@) {
+			push(@otherErrors, "for problem_id $UserProblem->problem_id) saw error: $@\n");
+		}
+	}
+
+	my $msg1 = (@sawRecordExists == 0) ? "" : join("",
+		"addUserMultipleProblems: the following user problems existed before ",
+		join(", ", @sawRecordExists), "\n");
+	if (@otherErrors) {
+		die join("", $msg1, @otherErrors);
+	} elsif (@sawRecordExists) {
+		croak $msg1;
+	}
+	return @ToReturn;
+}
+
 # versioned_ok is an optional argument which lets us slip versioned setIDs through checkArgs.
 sub putUserProblem {
 	my $V = $_[2] ? "V" : "";