MDEV-13826: Floating point exception in Filesort_tracker::print_json_members(Json_writer*)

Whenever Filesort_tracker has r_loops=0, r_ouptut_rows would be 0, so we should add the value zero
to the member "r_output_rows" explicitly

mysql-test/r/analyze_format_json.result

@@ -757,3 +757,63 @@ ANALYZE
   }
 }
 drop table t1,t2,t3;
+#
+# MDEV-13286: Floating point exception in Filesort_tracker::print_json_members(Json_writer*)
+#
+create table t0(a int);
+insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+create table t1 (a int, b int, c int);
+insert into t1 select a,a,a from t0;
+create table t2 as select * from t1;
+analyze format=json select a, (select t2.b from t2 where t2.a<t1.a order by t2.c limit 1) from t1 where t1.a<0;
+ANALYZE
+{
+  "query_block": {
+    "select_id": 1,
+    "r_loops": 1,
+    "r_total_time_ms": "REPLACED",
+    "table": {
+      "table_name": "t1",
+      "access_type": "ALL",
+      "r_loops": 1,
+      "rows": 10,
+      "r_rows": 10,
+      "r_total_time_ms": "REPLACED",
+      "filtered": 100,
+      "r_filtered": 0,
+      "attached_condition": "t1.a < 0"
+    },
+    "subqueries": [
+      {
+        "expression_cache": {
+          "state": "uninitialized",
+          "r_loops": 0,
+          "query_block": {
+            "select_id": 2,
+            "read_sorted_file": {
+              "r_rows": null,
+              "filesort": {
+                "sort_key": "t2.c",
+                "r_loops": null,
+                "r_limit": null,
+                "r_used_priority_queue": null,
+                "r_output_rows": null,
+                "table": {
+                  "table_name": "t2",
+                  "access_type": "ALL",
+                  "r_loops": 0,
+                  "rows": 10,
+                  "r_rows": null,
+                  "filtered": 100,
+                  "r_filtered": null,
+                  "attached_condition": "t2.a < t1.a"
+                }
+              }
+            }
+          }
+        }
+      }
+    ]
+  }
+}
+drop table t0,t1,t2;

mysql-test/t/analyze_format_json.test

@@ -212,3 +212,15 @@ GROUP BY sq ORDER BY gc;
 
 drop table t1,t2,t3;
 
+
+--echo #
+--echo # MDEV-13286: Floating point exception in Filesort_tracker::print_json_members(Json_writer*)
+--echo #
+create table t0(a int);
+insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+create table t1 (a int, b int, c int);
+insert into t1 select a,a,a from t0;
+create table t2 as select * from t1;
+--source include/analyze-format.inc
+analyze format=json select a, (select t2.b from t2 where t2.a<t1.a order by t2.c limit 1) from t1 where t1.a<0;
+drop table t0,t1,t2;

sql/sql_analyze_stmt.cc

@@ -26,6 +26,10 @@
 void Filesort_tracker::print_json_members(Json_writer *writer)
 {
   const char *varied_str= "(varied across executions)";
+
+  if (!get_r_loops())
+    writer->add_member("r_loops").add_null();
+  else
     writer->add_member("r_loops").add_ll(get_r_loops());
   
   if (get_r_loops() && time_tracker.timed)
@@ -36,20 +40,27 @@ void Filesort_tracker::print_json_members(Json_writer *writer)
   if (r_limit != HA_POS_ERROR)
   {
     writer->add_member("r_limit");
-    if (r_limit == 0)
+    if (!get_r_loops())
+      writer->add_null();
+    else if (r_limit == 0)
       writer->add_str(varied_str);
     else
       writer->add_ll((longlong) rint(r_limit/get_r_loops()));
   }
 
   writer->add_member("r_used_priority_queue"); 
-  if (r_used_pq == get_r_loops())
+  if (!get_r_loops())
+    writer->add_null();
+  else if (r_used_pq == get_r_loops())
     writer->add_bool(true);
   else if (r_used_pq == 0)
     writer->add_bool(false);
   else
     writer->add_str(varied_str);
 
+  if (!get_r_loops())
+    writer->add_member("r_output_rows").add_null();
+  else
     writer->add_member("r_output_rows").add_ll((longlong) rint(r_output_rows /
                                                               get_r_loops()));