a fix.

(Bug#3738: SQL_CALC_FOUND_ROWS ignores WHERE if LIMIT used,
 Bug#3845: wrong FOUND_ROWS result)

mysql-test/r/select_found.result

@@ -206,3 +206,20 @@ WHERE (  r = 1 AND a IN ( 1, 2    ) AND ( u = 'w'   OR u LIKE 'w/%'   ) )
 OR (  r = 1 AND a IN (       3 ) AND ( u = 'w/U' OR u LIKE 'w/U/%' ) )
 OR (  r = 1 AND a IN ( 1, 2, 3 ) AND ( u = 'w'                     ) );
 drop table t1;
+CREATE TABLE t1 (a VARCHAR(16), UNIQUE(a));
+INSERT INTO t1 VALUES ('1'), ('2'), ('3');
+SELECT SQL_CALC_FOUND_ROWS * FROM t1 WHERE a = '2' LIMIT 0, 1;
+a
+2
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+1
+DROP TABLE t1;
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (0), (0), (1), (2);
+SELECT SQL_CALC_FOUND_ROWS * FROM t1 WHERE a = 0 GROUP BY a HAVING a > 10;
+a
+SELECT FOUND_ROWS();
+FOUND_ROWS()
+0
+DROP TABLE t1;

mysql-test/t/select_found.test

@@ -127,3 +127,22 @@ WHERE (  r = 1 AND a IN ( 1, 2    ) AND ( u = 'w'   OR u LIKE 'w/%'   ) )
    OR (  r = 1 AND a IN ( 1, 2, 3 ) AND ( u = 'w'                     ) );
 drop table t1;
 
+#
+# Bug #3738: we have a ref key
+#
+
+CREATE TABLE t1 (a VARCHAR(16), UNIQUE(a));
+INSERT INTO t1 VALUES ('1'), ('2'), ('3');
+SELECT SQL_CALC_FOUND_ROWS * FROM t1 WHERE a = '2' LIMIT 0, 1;
+SELECT FOUND_ROWS();
+DROP TABLE t1;
+
+#
+# Bug #3845: group by, having and empty result
+#
+
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (0), (0), (1), (2);
+SELECT SQL_CALC_FOUND_ROWS * FROM t1 WHERE a = 0 GROUP BY a HAVING a > 10;
+SELECT FOUND_ROWS();
+DROP TABLE t1;

sql/sql_select.cc

@@ -5348,7 +5348,8 @@ end_send(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
 	if ((join->tables == 1) && !join->tmp_table && !join->sort_and_group
 	    && !join->send_group_parts && !join->having && !jt->select_cond &&
 	    !(jt->select && jt->select->quick) &&
-	    !(jt->table->file->table_flags() & HA_NOT_EXACT_COUNT))
+	    !(jt->table->file->table_flags() & HA_NOT_EXACT_COUNT) &&
+            (jt->ref.key < 0))
 	{
 	  /* Join over all rows in table;  Return number of found rows */
 	  TABLE *table=jt->table;
@@ -5429,6 +5430,7 @@ end_send_group(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
 	  DBUG_RETURN(-1);			/* purecov: inspected */
 	if (end_of_records)
 	{
+	  if (!error)
             join->send_records++;
 	  DBUG_RETURN(0);
 	}