size_regulator: make the DB access more efficient

The query to get counts of unsent results for various size classes
did a sequential scan, which isn't practical for large projects.
All we care about is the count up to a certain (low) limit,
so I replaced it with an enumeration with a limit, and count the results.

clientgui/sg_TaskPanel.cpp

@@ -494,6 +494,7 @@ CSimpleTaskPanel::CSimpleTaskPanel( wxWindow* parent ) :
     wxBoxSizer* bSizer3;
     bSizer3 = new wxBoxSizer( wxHORIZONTAL );
     
+    // what project the task is from, e.g. "From: SETI@home"
     m_TaskProjectLabel = new CTransparentStaticText( this, wxID_ANY, _("From:"), wxDefaultPosition, wxDefaultSize, 0 );
     m_TaskProjectLabel->Wrap( -1 );
     bSizer3->Add( m_TaskProjectLabel, 0, wxRIGHT, ADJUSTFORXDPI(5) );

db/boinc_db.cpp

@@ -1138,6 +1138,38 @@ void DB_RESULT::db_parse(MYSQL_ROW &r) {
     peak_disk_usage = atof(r[i++]);
 }
 
+// faster version.
+// return unsent count up to a max of "count_max"
+//
+int DB_RESULT::get_unsent_counts(APP& app, int* unsent_count, int count_max) {
+    char query[1024];
+    int retval;
+    MYSQL_RES *rp;
+
+    for (int i=0; i<app.n_size_classes; i++) {
+        sprintf(query,
+            "select id from result where appid=%d and server_state=%d and size_class=%d limit %d",
+            app.id, RESULT_SERVER_STATE_UNSENT, i, count_max
+        );
+        retval = db->do_query(query);
+        if (retval) return mysql_errno(db->mysql);
+        rp = mysql_store_result(db->mysql);
+        if (!rp) return mysql_errno(db->mysql);
+        int count = 0;
+        while (1) {
+            MYSQL_ROW row = mysql_fetch_row(rp);
+            if (!row) break;
+            count++;
+        }
+        mysql_free_result(rp);
+        unsent_count[i] = count;
+    }
+    return 0;
+}
+
+#if 0
+// the following is too slow if result table is large.
+//
 int DB_RESULT::get_unsent_counts(APP& app, int* unsent_count) {
     char query[1024];
     MYSQL_RES *rp;
@@ -1169,6 +1201,7 @@ int DB_RESULT::get_unsent_counts(APP& app, int* unsent_count) {
     mysql_free_result(rp);
     return retval;
 }
+#endif
 
 int DB_RESULT::make_unsent(
     APP& app, int size_class, int n, const char* order_clause, int& nchanged

db/boinc_db.h

@@ -184,7 +184,7 @@ public:
     void db_print_values(char*);
     void db_parse(MYSQL_ROW &row);
     void operator=(RESULT& r) {RESULT::operator=(r);}
-    int get_unsent_counts(APP&, int* unsent);
+    int get_unsent_counts(APP&, int* unsent, int count_max);
     int make_unsent(
         APP&, int size_class, int n, const char* order_clause, int& nchanged
     );

sched/size_regulator.cpp

@@ -15,8 +15,8 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with BOINC.  If not, see <http://www.gnu.org/licenses/>.
 
-// daemon to regulate the transition of jobs from INACTIVE to UNSENT,
-// to maintain a buffer of UNSENT jobs of each size class.
+// daemon to regulate the transition of results from INACTIVE to UNSENT,
+// to maintain a buffer of UNSENT results of each size class.
 
 #include <stdio.h>
 
@@ -43,7 +43,7 @@ void usage(){
 int do_pass(bool& action) {
     DB_RESULT result;
     int unsent[100];
-    int retval = result.get_unsent_counts(app, unsent);
+    int retval = result.get_unsent_counts(app, unsent, hi);
     if (retval) return retval;
     action = false;
     for (int i=0; i<app.n_size_classes; i++) {