MDEV-26737: Outdated VARIABLE_COMMENT for HISTOGRAM_TYPE in I_S.SYSTEM_VARIABLES

Fix the description

mysql-test/main/mysqld--help.result

@@ -368,7 +368,8 @@ The following specify which files/extra groups are read (specified before remain
  Specifies type of the histograms created by ANALYZE.
  Possible values are: SINGLE_PREC_HB - single precision
  height-balanced, DOUBLE_PREC_HB - double precision
- height-balanced.
+ height-balanced, JSON_HB - height-balanced, stored as
+ JSON.
  --host-cache-size=# How many host names should be cached to avoid resolving.
  (Automatically configured unless set explicitly)
  --idle-readonly-transaction-timeout=# 

mysql-test/main/statistics_json.result

@@ -7940,3 +7940,9 @@ test.t1	analyze	status	OK
 SELECT * FROM t1 WHERE f > 'qux';
 f
 DROP TABLE t1;
+#
+# MDEV-26737: Outdated VARIABLE_COMMENT for HISTOGRAM_TYPE in I_S.SYSTEM_VARIABLES
+#
+select variable_comment from information_schema.system_variables where VARIABLE_NAME='HISTOGRAM_TYPE';
+variable_comment
+Specifies type of the histograms created by ANALYZE. Possible values are: SINGLE_PREC_HB - single precision height-balanced, DOUBLE_PREC_HB - double precision height-balanced, JSON_HB - height-balanced, stored as JSON.

mysql-test/main/statistics_json.test

@@ -242,3 +242,8 @@ ANALYZE TABLE t1 PERSISTENT FOR ALL;
 SELECT * FROM t1 WHERE f > 'qux';
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-26737: Outdated VARIABLE_COMMENT for HISTOGRAM_TYPE in I_S.SYSTEM_VARIABLES
+--echo #
+select variable_comment from information_schema.system_variables where VARIABLE_NAME='HISTOGRAM_TYPE';
+

sql/sys_vars.cc

@@ -6496,7 +6496,8 @@ static Sys_var_enum Sys_histogram_type(
        "Specifies type of the histograms created by ANALYZE. "
        "Possible values are: "
        "SINGLE_PREC_HB - single precision height-balanced, "
-       "DOUBLE_PREC_HB - double precision height-balanced.",
+       "DOUBLE_PREC_HB - double precision height-balanced, "
+       "JSON_HB - height-balanced, stored as JSON.",
        SESSION_VAR(histogram_type), CMD_LINE(REQUIRED_ARG),
        histogram_types, DEFAULT(1));