From 79cdb535da8c4128a4572297d264ca8e4a0ba70d Mon Sep 17 00:00:00 2001
From: Michael Okoko <okokomichaels@outlook.com>
Date: Mon, 14 Jun 2021 17:14:11 +0100
Subject: add json statistics test and change histogram column type to blob

---
 mysql-test/main/statistics_json.test | 28 ++++++++++++++++++++++++++++
 scripts/mysql_system_tables.sql      |  2 +-
 sql/sql_statistics.cc                |  5 +++--
 3 files changed, 32 insertions(+), 3 deletions(-)
 create mode 100644 mysql-test/main/statistics_json.test

diff --git a/mysql-test/main/statistics_json.test b/mysql-test/main/statistics_json.test
new file mode 100644
index 00000000000..0af7d1f6d1d
--- /dev/null
+++ b/mysql-test/main/statistics_json.test
@@ -0,0 +1,28 @@
+--source include/have_stat_tables.inc
+--echo #
+--echo # Test that JSON is a valid histogram type and we can store JSON strings in mysql.column_stats
+--echo #
+--disable_warnings
+drop table if exists t1;
+--enable_warnings
+
+set @save_histogram_type=@@histogram_type;
+
+CREATE TABLE t1 (
+  a int NOT NULL PRIMARY KEY,
+  b varchar(32)
+) ENGINE=MYISAM;
+
+SET histogram_type='JSON';
+SELECT @@histogram_type;
+
+INSERT INTO t1 VALUES
+  (7, 'xxxxxxxxxxxxxxxxxxxxxxxxxx'),
+  (17, 'vvvvvvvvvvvvv');
+
+ANALYZE TABLE t1 PERSISTENT FOR COLUMNS(b) INDEXES();
+DESCRIBE mysql.column_stats;
+SELECT * FROM mysql.column_stats;
+
+set histogram_type=@save_histogram_type;
+DROP TABLE t1;
\ No newline at end of file
diff --git a/scripts/mysql_system_tables.sql b/scripts/mysql_system_tables.sql
index 353f6658447..e31f3372b5f 100644
--- a/scripts/mysql_system_tables.sql
+++ b/scripts/mysql_system_tables.sql
@@ -314,7 +314,7 @@ DROP TABLE tmp_proxies_priv;
 
 CREATE TABLE IF NOT EXISTS table_stats (db_name varchar(64) NOT NULL, table_name varchar(64) NOT NULL, cardinality bigint(21) unsigned DEFAULT NULL, PRIMARY KEY (db_name,table_name) ) engine=Aria transactional=0 CHARACTER SET utf8 COLLATE utf8_bin comment='Statistics on Tables';
 
-CREATE TABLE IF NOT EXISTS column_stats (db_name varchar(64) NOT NULL, table_name varchar(64) NOT NULL, column_name varchar(64) NOT NULL, min_value varbinary(255) DEFAULT NULL, max_value varbinary(255) DEFAULT NULL, nulls_ratio decimal(12,4) DEFAULT NULL, avg_length decimal(12,4) DEFAULT NULL, avg_frequency decimal(12,4) DEFAULT NULL, hist_size tinyint unsigned, hist_type enum('SINGLE_PREC_HB','DOUBLE_PREC_HB','JSON'), histogram varbinary(255), PRIMARY KEY (db_name,table_name,column_name) ) engine=Aria transactional=0 CHARACTER SET utf8 COLLATE utf8_bin comment='Statistics on Columns';
+CREATE TABLE IF NOT EXISTS column_stats (db_name varchar(64) NOT NULL, table_name varchar(64) NOT NULL, column_name varchar(64) NOT NULL, min_value varbinary(255) DEFAULT NULL, max_value varbinary(255) DEFAULT NULL, nulls_ratio decimal(12,4) DEFAULT NULL, avg_length decimal(12,4) DEFAULT NULL, avg_frequency decimal(12,4) DEFAULT NULL, hist_size tinyint unsigned, hist_type enum('SINGLE_PREC_HB','DOUBLE_PREC_HB','JSON'), histogram blob, PRIMARY KEY (db_name,table_name,column_name) ) engine=Aria transactional=0 CHARACTER SET utf8 COLLATE utf8_bin comment='Statistics on Columns';
 
 CREATE TABLE IF NOT EXISTS index_stats (db_name varchar(64) NOT NULL, table_name varchar(64) NOT NULL, index_name varchar(64) NOT NULL, prefix_arity int(11) unsigned NOT NULL, avg_frequency decimal(12,4) DEFAULT NULL, PRIMARY KEY (db_name,table_name,index_name,prefix_arity) ) engine=Aria transactional=0 CHARACTER SET utf8 COLLATE utf8_bin comment='Statistics on Indexes';
 
diff --git a/sql/sql_statistics.cc b/sql/sql_statistics.cc
index 5e78738c184..16e3e8b1664 100644
--- a/sql/sql_statistics.cc
+++ b/sql/sql_statistics.cc
@@ -183,7 +183,7 @@ TABLE_FIELD_TYPE column_stat_fields[COLUMN_STAT_N_FIELDS] =
   },
   {
     { STRING_WITH_LEN("histogram") },
-    { STRING_WITH_LEN("varbinary(255)") },
+    { STRING_WITH_LEN("blob") },
     { NULL, 0 }
   }
 };
@@ -1071,7 +1071,8 @@ public:
           break;
         case COLUMN_STAT_HISTOGRAM:
           if (stats->histogram.get_type() == JSON) {
-            stat_field->store((char *) "hello_world", 11, &my_charset_bin);
+            const char* val = "{'hello': 'world'}";
+            stat_field->store(val, strlen(val), &my_charset_bin);
           } else {
             stat_field->store((char *) stats->histogram.get_values(),
                               stats->histogram.get_size(), &my_charset_bin);
-- 
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