Plan at least one task from each group

Signed-off-by: Filip Petkovski <filip.petkovsky@gmail.com>

pkg/compact/compact.go

@@ -1382,6 +1382,12 @@ func (c *BucketCompactor) planTasks(ctx context.Context, groups []*Group) ([]Gro
 	}
 
 	tasksLimit := c.concurrency
+	// Make sure we plan at least one task from each group.
+	if tasksLimit < len(allTasks) {
+		tasksLimit = len(groups)
+	}
+
+	// If there aren't enough tasks across all groups, plan all available tasks.
 	if numTasks < tasksLimit {
 		tasksLimit = numTasks
 	}

pkg/compact/compact_e2e_test.go

@@ -174,7 +174,11 @@ func TestGroupCompactE2E(t *testing.T) {
 	testGroupCompactE2e(t, nil, 2)
 }
 
-func TestGroupCompactE2EWithConcurrency(t *testing.T) {
+func TestGroupCompactE2EWithoutConcurrency(t *testing.T) {
+	testGroupCompactE2e(t, nil, 1)
+}
+
+func TestGroupCompactE2EWithHighConcurrency(t *testing.T) {
 	testGroupCompactE2e(t, nil, 20)
 }