[MDEV-18306] Optimizer_trace has invalid JSON near rows_estimation Created: 2019-01-18  Updated: 2019-02-13  Resolved: 2019-02-13

Status: Closed
Project: MariaDB Server
Component/s: Optimizer
Affects Version/s: N/A
Fix Version/s: N/A

Type: Bug Priority: Major
Reporter: Sergei Petrunia Assignee: Varun Gupta (Inactive)
Resolution: Fixed Votes: 0
Labels: None

Issue Links:
PartOf
is part of MDEV-6111 optimizer trace Closed

 Description   

I thought that improvements to JSON writer would make this impossible, but
somehow they didn't? 

create table ten(a int);
 
insert into ten values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
 
set optimizer_trace=1;
 
select * from ten where a<3 ;

produces:

        "steps": [
 
          {
 
             ...
 
          },
 
          ...
 
          {
 
            "ref_optimizer_key_uses": []
 
          },
 
          "rows_estimation": [
 
            {
 
              "selectivity_for_indexes": [],
 
              "selectivity_for_columns": []
 
            },
 
            {
 
              "table": "ten",
 
              "table_scan": {
 
                "rows": 10,
 
                "cost": 1
 
              }
 
            }
 
          ],

Note that "rows_estimation" is a named element, but it is in the "steps" array.

 Comments   
Comment by Sergei Petrunia [ 2019-01-18 ]

execution_plan_for_potential_materialization has the same problem.

Comment by Varun Gupta (Inactive) [ 2019-01-21 ]

I added a small patch to see the above irregularity

--- a/sql/sql_select.cc
 
+++ b/sql/sql_select.cc
 
@@ -61,6 +61,7 @@
 
 #include <my_bit.h>
 
 #include <hash.h>
 
 #include <ft_global.h>
 
+#include "my_json_writer.h"
 
 
 /*
 
   A key part number that means we're using a fulltext scan.
 
@@ -1214,6 +1215,14 @@ JOIN::optimize_inner()
 
   set_allowed_join_cache_types();
 
   need_distinct= TRUE;
 
+  {
 
+    Json_writer wri;
 
+    wri.start_array();
 
+    wri.add_member("varun").start_object();
 
+    wri.end_object();
 
+    wri.end_array();
 
+  }
 
+

And there is no assert failure , we are trying to add a key-value pair to the array which is incorrect accoring to JSON standards

Comment by Varun Gupta (Inactive) [ 2019-02-13 ]

Fixed as a part of MDEV-6111

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