Estimation for filtered rows less precise with JSON histogram comparing to DOUBLE_PREC (#6)

--source include/have_sequence.inc

create table t1 (a char(1)) engine=MyISAM;

insert into t1 select chr(seq%26+97) from seq_1_to_50;

insert into t1 select ':' from t1;

select count(*) from t1 where a <> 'a';

set histogram_type=JSON_HB;

analyze table t1 persistent for all;

explain format=json select COUNT(*) FROM t1 WHERE a <> 'a';

set histogram_type=DOUBLE_PREC_HB;

analyze table t1 persistent for all;

explain format=json select COUNT(*) FROM t1 WHERE a <> 'a';

# Cleanup

drop table t1;

select count(*) from t1 where a <> 'a';

count(*)

99

  "query_block": {

    "select_id": 1,

    "nested_loop": [

      {

        "table": {

          "table_name": "t1",

          "access_type": "ALL",

          "rows": 100,

          "filtered": 100,

          "attached_condition": "t1.a <> 'a'"

        }

      }

    ]

  }

  "query_block": {

    "select_id": 1,

    "nested_loop": [

      {

        "table": {

          "table_name": "t1",

          "access_type": "ALL",

          "rows": 100,

          "filtered": 52.70370102,

          "attached_condition": "t1.a <> 'a'"

        }

      }

    ]

  }