MDEV-25151 JSON_TABLE: Unexpectedly padded values in a PATH column.

Field length can increase after the change_charset(), so need to
set field->ptr properly.

also sensitive parts of the test moved to json_not_embedded.test.

mysql-test/suite/json/r/json_table.result

@@ -98,26 +98,6 @@ a
 1
 connection default;
 disconnect con1;
-create database db;
-use db;
-create table t (a text);
-insert into t values ('{"foo":"bar"}');
-create user u@localhost;
-grant select (a) on db.t to u@localhost;
-connect  con1,localhost,u,,db;
-select a from t;
-a
-{"foo":"bar"}
-select * from t, json_table(t.a, '$' columns(f varchar(20) path '$.foo')) as jt;
-a	f
-{"foo":"bar"}	bar
-select * into outfile 'f' from json_table('[]', '$' columns(x for ordinality)) q;
-ERROR 28000: Access denied for user 'u'@'localhost' (using password: NO)
-connection default;
-disconnect con1;
-drop user u@localhost;
-drop database db;
-use test;
 create table t1 (
 color varchar(32),
 price int
@@ -515,5 +495,15 @@ a
 SELECT a, b FROM JSON_TABLE('[]', '$' COLUMNS (a FOR ORDINALITY, b INT PATH '$[*]' ERROR ON EMPTY)) AS t ORDER BY a;
 ERROR HY000: Field 'b' can't be set for JSON_TABLE 't'.
 #
+# MDEV-25151 JSON_TABLE: Unexpectedly padded values in a PATH column.
+#
+SET @old_character_set_connection= @@character_set_connection;
+SET @@character_set_connection= utf8;
+select hex(a), b from json_table('["foo","bar"]','$[*]' columns (a char(3) path '$', b for ordinality)) t;
+hex(a)	b
+666F6F	1
+626172	2
+SET @@character_set_connection= @old_character_set_connection;
+#
 # End of 10.6 tests
 #

mysql-test/suite/json/r/json_table_notembedded.result

+create database db;
+use db;
+create table t (a text);
+insert into t values ('{"foo":"bar"}');
+create user u@localhost;
+grant select (a) on db.t to u@localhost;
+connect  con1,localhost,u,,db;
+select a from t;
+a
+{"foo":"bar"}
+select * from t, json_table(t.a, '$' columns(f varchar(20) path '$.foo')) as jt;
+a	f
+{"foo":"bar"}	bar
+select * into outfile 'f' from json_table('[]', '$' columns(x for ordinality)) q;
+ERROR 28000: Access denied for user 'u'@'localhost' (using password: NO)
+connection default;
+disconnect con1;
+drop user u@localhost;
+drop database db;
+use test;

mysql-test/suite/json/t/json_table.test

@@ -59,34 +59,6 @@ select a from json_table('{"a":0}',"$" columns(a for ordinality)) foo;
 connection default;
 disconnect con1;
 
-#
-# MDEV-22302 JSON_TABLE: Column privilege is insufficient for query with json_table
-#
-
-create database db;
-use db;
-create table t (a text);
-insert into t values ('{"foo":"bar"}');
-create user u@localhost;
-grant select (a) on db.t to u@localhost;
- 
---connect (con1,localhost,u,,db)
-select a from t;
-select * from t, json_table(t.a, '$' columns(f varchar(20) path '$.foo')) as jt;
-
-#
-# MDEV-25141 JSON_TABLE: SELECT into outfile bypasses file privilege check
-#
---error ER_ACCESS_DENIED_ERROR
-select * into outfile 'f' from json_table('[]', '$' columns(x for ordinality)) q;
-
-connection default;
-disconnect con1;
-
-drop user u@localhost;
-drop database db;
-
-use test;
 create table t1 (
       color varchar(32),
         price int
@@ -407,6 +379,14 @@ EXECUTE stmt;
 --error ER_JSON_TABLE_ERROR_ON_FIELD
 SELECT a, b FROM JSON_TABLE('[]', '$' COLUMNS (a FOR ORDINALITY, b INT PATH '$[*]' ERROR ON EMPTY)) AS t ORDER BY a;
 
+--echo #
+--echo # MDEV-25151 JSON_TABLE: Unexpectedly padded values in a PATH column.
+--echo #
+SET @old_character_set_connection= @@character_set_connection;
+SET @@character_set_connection= utf8;
+select hex(a), b from json_table('["foo","bar"]','$[*]' columns (a char(3) path '$', b for ordinality)) t;
+SET @@character_set_connection= @old_character_set_connection;
+
 --echo #
 --echo # End of 10.6 tests
 --echo #

mysql-test/suite/json/t/json_table_notembedded.test

+source include/not_embedded.inc;
+
+#
+# MDEV-22302 JSON_TABLE: Column privilege is insufficient for query with json_table
+#
+
+create database db;
+use db;
+create table t (a text);
+insert into t values ('{"foo":"bar"}');
+create user u@localhost;
+grant select (a) on db.t to u@localhost;
+ 
+--connect (con1,localhost,u,,db)
+select a from t;
+select * from t, json_table(t.a, '$' columns(f varchar(20) path '$.foo')) as jt;
+
+#
+# MDEV-25141 JSON_TABLE: SELECT into outfile bypasses file privilege check
+#
+--error ER_ACCESS_DENIED_ERROR
+select * into outfile 'f' from json_table('[]', '$' columns(x for ordinality)) q;
+
+connection default;
+disconnect con1;
+
+drop user u@localhost;
+drop database db;
+
+use test;

sql/json_table.cc

@@ -1134,12 +1134,31 @@ int Table_function_json_table::setup(THD *thd, TABLE_LIST *sql_table,
   }
 
   {
+    /*
+      The m_json defines it's charset during the fix_fields stage so we're
+      changing the field's current charsets with it.
+      The complicated part is that the length of the field can be changed so
+      in this case we should move all the consequent fiedlds.
+    */
     List_iterator_fast<Json_table_column> jc_i(m_columns);
-    for (uint i= 0; t->field[i]; i++)
+    int field_offset= 0;
+    Field *f;
+    for (uint i= 0; (f= t->field[i]); i++)
     {
       Json_table_column *jc= jc_i++;
-      t->field[i]->change_charset(
+      uint32 old_pack_length= f->pack_length();
+
+      f->change_charset(
            jc->m_explicit_cs ? jc->m_explicit_cs : m_json->collation);
+
+      if (field_offset)
+      {
+        f->move_field(f->ptr + field_offset, f->null_ptr, f->null_bit);
+        f->reset();
+      }
+
+      field_offset= (field_offset + f->pack_length()) - old_pack_length;
+
       /*
         The m_field->charset is going to be reused if it's the prepared
         statement running several times. So should restored the original