MDEV-27036: re-enable my_json_writer-t unit test

17 files changed, 199 insertions, 152 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5c045360631..22f3f1101a4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -142,6 +142,7 @@ IF (NOT CPACK_GENERATOR)
   ENDIF(WIN32) 
 ENDIF(NOT CPACK_GENERATOR)
 
+INCLUDE(build_depends)
 INCLUDE(FeatureSummary)
 INCLUDE(misc)
 INCLUDE(mysql_version)
@@ -538,8 +539,6 @@ IF(UNIX)
   INSTALL_DOCUMENTATION(Docs/INSTALL-BINARY Docs/README-wsrep COMPONENT Readme)
 ENDIF()
 
-INCLUDE(build_depends)
-
 INCLUDE(CPack)
 
 IF(WIN32 AND SIGNCODE)
diff --git a/cmake/ctest.cmake b/cmake/ctest.cmake
index 5bc1ce5f832..db0defa1869 100644
--- a/cmake/ctest.cmake
+++ b/cmake/ctest.cmake
@@ -22,3 +22,4 @@ MACRO(MY_ADD_TESTS)
   ENDFOREACH()
 ENDMACRO()
 
+FIND_PACKAGE(Boost COMPONENTS unit_test_framework)
diff --git a/include/my_dir.h b/include/my_dir.h
index 12cf5db149d..2f152844e7e 100644
--- a/include/my_dir.h
+++ b/include/my_dir.h
@@ -17,6 +17,9 @@
 #define MY_DIR_H
 
 #include <sys/stat.h>
+#include <stddef.h>
+
+#include "my_global.h"
 
 #ifdef	__cplusplus
 extern "C" {
diff --git a/sql/CMakeLists.txt b/sql/CMakeLists.txt
index 73a574aed8a..dacdfdd2e2b 100644
--- a/sql/CMakeLists.txt
+++ b/sql/CMakeLists.txt
@@ -206,7 +206,7 @@ RECOMPILE_FOR_EMBEDDED)
 ADD_LIBRARY(sql STATIC ${SQL_SOURCE})
 MAYBE_DISABLE_IPO(sql)
 DTRACE_INSTRUMENT(sql)
-TARGET_LINK_LIBRARIES(sql
+TARGET_LINK_LIBRARIES(sql PUBLIC
   mysys mysys_ssl dbug strings vio pcre2-8
   ${FMT_LIBRARIES}
   tpool
@@ -221,7 +221,7 @@ ENDIF()
 FOREACH(se aria partition perfschema sql_sequence wsrep)
   # These engines are used directly in sql sources.
   IF(TARGET ${se})
-    TARGET_LINK_LIBRARIES(sql ${se})
+    TARGET_LINK_LIBRARIES(sql PUBLIC ${se})
   ENDIF()
 ENDFOREACH()
 
diff --git a/sql/my_json_writer.cc b/sql/my_json_writer.cc
index 8284c9bbfca..8bc582c50a8 100644
--- a/sql/my_json_writer.cc
+++ b/sql/my_json_writer.cc
@@ -13,10 +13,14 @@
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */
 
+#include "my_json_writer.h"
+
+#include "sql_class.h"
 #include "mariadb.h"
 #include "sql_priv.h"
 #include "sql_string.h"
-#include "my_json_writer.h"
+#include "log.h"
+
 
 #if !defined(NDEBUG) || defined(JSON_WRITER_UNIT_TEST)
 #include <iostream>
@@ -328,6 +332,7 @@ Json_writer_temp_disable::Json_writer_temp_disable(THD *thd_arg)
   thd= thd_arg;
   thd->opt_trace.disable_tracing_if_required();
 }
+
 Json_writer_temp_disable::~Json_writer_temp_disable()
 {
   thd->opt_trace.enable_tracing_if_required();
@@ -497,3 +502,18 @@ void Single_line_formatting_helper::disable_and_flush()
   state= INACTIVE;
 }
 
+
+Json_writer_struct::Json_writer_struct(THD *thd)
+    : Json_writer_struct(thd->opt_trace.get_current_json())
+{
+}
+
+Json_writer_object::Json_writer_object(THD *thd, const char *str)
+    : Json_writer_object(thd->opt_trace.get_current_json(), str)
+{
+}
+
+Json_writer_array::Json_writer_array(THD *thd, const char *str)
+    : Json_writer_array(thd->opt_trace.get_current_json(), str)
+{
+}
diff --git a/sql/my_json_writer.h b/sql/my_json_writer.h
index a4e8c825582..201e3136c08 100644
--- a/sql/my_json_writer.h
+++ b/sql/my_json_writer.h
@@ -17,7 +17,6 @@
 #define JSON_WRITER_INCLUDED
 
 #include "my_base.h"
-#include "sql_select.h"
 
 #if !defined(NDEBUG) || defined(JSON_WRITER_UNIT_TEST) || defined ENABLED_JSON_WRITER_CONSISTENCY_CHECKS
 #include <set>
@@ -32,6 +31,7 @@ constexpr uint FAKE_SELECT_LEX_ID= UINT_MAX;
 // Also, mock objects are defined in my_json_writer-t.cc
 #define VALIDITY_ASSERT(x) if (!(x)) this->invalid_json= true;
 #else
+#include "sql_select.h"
 #define VALIDITY_ASSERT(x) DBUG_ASSERT(x)
 #endif
 
@@ -40,8 +40,11 @@ constexpr uint FAKE_SELECT_LEX_ID= UINT_MAX;
 class Opt_trace_stmt;
 class Opt_trace_context;
 class Json_writer;
+struct TABLE;
 struct TABLE_LIST;
 
+struct st_join_table;
+using JOIN_TAB= struct st_join_table;
 
 /*
   Single_line_formatting_helper is used by Json_writer to do better formatting
@@ -387,10 +390,7 @@ protected:
     named_items_expectation.push_back(expect_named_children);
 #endif
   }
-  explicit Json_writer_struct(THD *thd)
-  : Json_writer_struct(thd->opt_trace.get_current_json())
-  {
-  }
+  explicit Json_writer_struct(THD *thd);
 
 public:
 
@@ -446,10 +446,7 @@ public:
     }
   }
 
-  explicit Json_writer_object(THD* thd, const char *str= nullptr)
-  : Json_writer_object(thd->opt_trace.get_current_json(), str)
-  {
-  }
+  explicit Json_writer_object(THD* thd, const char *str= nullptr);
 
   ~Json_writer_object()
   {
@@ -619,10 +616,7 @@ public:
     }
   }
 
-  explicit Json_writer_array(THD *thd, const char *str= nullptr)
-    : Json_writer_array(thd->opt_trace.get_current_json(), str)
-  {
-  }
+  explicit Json_writer_array(THD *thd, const char *str= nullptr);
 
   ~Json_writer_array()
   {
diff --git a/sql/opt_range.cc b/sql/opt_range.cc
index 06063cb9ae1..2ef30924aa5 100644
--- a/sql/opt_range.cc
+++ b/sql/opt_range.cc
@@ -1254,6 +1254,14 @@ void SQL_SELECT::cleanup()
   close_cached_file(&file);
 }
 
+int SQL_SELECT::skip_record(THD *thd)
+{
+    int rc= MY_TEST(!cond || cond->val_int());
+    if (thd->is_error())
+        rc= -1;
+    return rc;
+}
+
 
 SQL_SELECT::~SQL_SELECT()
 {
@@ -1872,6 +1880,20 @@ QUICK_RANGE::QUICK_RANGE()
   min_keypart_map(0), max_keypart_map(0)
 {}
 
+QUICK_RANGE::QUICK_RANGE(THD *thd, const uchar *min_key_arg, uint min_length_arg, key_part_map min_keypart_map_arg, const uchar *max_key_arg, uint max_length_arg, key_part_map max_keypart_map_arg, uint flag_arg)
+: min_key((uchar*) thd->memdup(min_key_arg, min_length_arg + 1)),
+  max_key((uchar*) thd->memdup(max_key_arg, max_length_arg + 1)),
+  min_length((uint16) min_length_arg),
+  max_length((uint16) max_length_arg),
+  flag((uint16) flag_arg),
+  min_keypart_map(min_keypart_map_arg),
+  max_keypart_map(max_keypart_map_arg)
+{
+#ifdef HAVE_valgrind
+  dummy=0;
+#endif
+}
+
 SEL_ARG::SEL_ARG(SEL_ARG &arg) :Sql_alloc()
 {
   type=arg.type;
@@ -10848,6 +10870,31 @@ uint SEL_ARG::get_max_key_part() const
   return max_part;
 }
 
+SEL_ARG *SEL_ARG::clone_and(THD *thd, SEL_ARG *arg)
+{						// Get overlapping range
+  uchar *new_min,*new_max;
+  uint8 flag_min,flag_max;
+  if (cmp_min_to_min(arg) >= 0)
+  {
+    new_min=min_value; flag_min=min_flag;
+  }
+  else
+  {
+    new_min=arg->min_value; flag_min=arg->min_flag; /* purecov: deadcode */
+  }
+  if (cmp_max_to_max(arg) <= 0)
+  {
+    new_max=max_value; flag_max=max_flag;
+  }
+  else
+  {
+    new_max=arg->max_value; flag_max=arg->max_flag;
+  }
+  return new (thd->mem_root) SEL_ARG(field, part, new_min, new_max, flag_min,
+                                     flag_max,
+                                     MY_TEST(maybe_flag && arg->maybe_flag));
+}
+
 
 /*
   Remove the SEL_ARG graph elements which have part > max_part.
@@ -16568,3 +16615,11 @@ void print_keyparts_name(String *out, const KEY_PART_INFO *key_part,
   }
   out->append(STRING_WITH_LEN(")"));
 }
+
+bool RANGE_OPT_PARAM::statement_should_be_aborted() const
+{
+  return thd->killed
+      || thd->is_fatal_error
+      || thd->is_error()
+      || alloced_sel_args > SEL_ARG::MAX_SEL_ARGS;
+}
diff --git a/sql/opt_range.h b/sql/opt_range.h
index 1014176ecc5..65e2d6db9ae 100644
--- a/sql/opt_range.h
+++ b/sql/opt_range.h
@@ -36,8 +36,9 @@
 #include "sql_class.h"                          // set_var.h: THD
 #include "set_var.h"                            /* Item */
 
-class JOIN;
 class Item_sum;
+class JOIN;
+class Unique;
 
 struct KEY_PART {
   uint16           key,part;
@@ -389,30 +390,7 @@ public:
   {
     return sel_cmp(field,max_value, arg->min_value, max_flag, arg->min_flag);
   }
-  SEL_ARG *clone_and(THD *thd, SEL_ARG* arg)
-  {						// Get overlapping range
-    uchar *new_min,*new_max;
-    uint8 flag_min,flag_max;
-    if (cmp_min_to_min(arg) >= 0)
-    {
-      new_min=min_value; flag_min=min_flag;
-    }
-    else
-    {
-      new_min=arg->min_value; flag_min=arg->min_flag; /* purecov: deadcode */
-    }
-    if (cmp_max_to_max(arg) <= 0)
-    {
-      new_max=max_value; flag_max=max_flag;
-    }
-    else
-    {
-      new_max=arg->max_value; flag_max=arg->max_flag;
-    }
-    return new (thd->mem_root) SEL_ARG(field, part, new_min, new_max, flag_min,
-                                       flag_max,
-                                       MY_TEST(maybe_flag && arg->maybe_flag));
-  }
+  SEL_ARG *clone_and(THD *thd, SEL_ARG* arg);
   SEL_ARG *clone_first(SEL_ARG *arg)
   {						// min <= X < arg->min
     return new SEL_ARG(field,part, min_value, arg->min_value,
@@ -733,14 +711,7 @@ public:
   bool force_default_mrr;
   KEY_PART *key[MAX_KEY]; /* First key parts of keys used in the query */
 
-  bool statement_should_be_aborted() const
-  {
-    return
-      thd->killed ||
-      thd->is_fatal_error ||
-      thd->is_error() ||
-      alloced_sel_args > SEL_ARG::MAX_SEL_ARGS;
-  }
+  bool statement_should_be_aborted() const;
 };
 
 
@@ -763,21 +734,9 @@ class QUICK_RANGE :public Sql_alloc {
   QUICK_RANGE();				/* Full range */
   QUICK_RANGE(THD *thd, const uchar *min_key_arg, uint min_length_arg,
               key_part_map min_keypart_map_arg,
-	      const uchar *max_key_arg, uint max_length_arg,
+              const uchar *max_key_arg, uint max_length_arg,
               key_part_map max_keypart_map_arg,
-	      uint flag_arg)
-    : min_key((uchar*) thd->memdup(min_key_arg, min_length_arg + 1)),
-      max_key((uchar*) thd->memdup(max_key_arg, max_length_arg + 1)),
-      min_length((uint16) min_length_arg),
-      max_length((uint16) max_length_arg),
-      flag((uint16) flag_arg),
-      min_keypart_map(min_keypart_map_arg),
-      max_keypart_map(max_keypart_map_arg)
-    {
-#ifdef HAVE_valgrind
-      dummy=0;
-#endif
-    }
+              uint flag_arg);
 
   /**
      Initalizes a key_range object for communication with storage engine. 
@@ -1724,13 +1683,7 @@ class SQL_SELECT :public Sql_alloc {
      -1   if error
       1   otherwise
   */   
-  inline int skip_record(THD *thd)
-  {
-    int rc= MY_TEST(!cond || cond->val_int());
-    if (thd->is_error())
-      rc= -1;
-    return rc;
-  }
+  int skip_record(THD *thd);
   int test_quick_select(THD *thd, key_map keys, table_map prev_tables,
 			ha_rows limit, bool force_quick_range, 
                         bool ordered_output, bool remove_false_parts_of_where,
diff --git a/sql/set_var.cc b/sql/set_var.cc
index 4b3e23b06c0..07e378e50d1 100644
--- a/sql/set_var.cc
+++ b/sql/set_var.cc
@@ -241,6 +241,11 @@ const uchar *sys_var::global_value_ptr(THD *thd, const LEX_CSTRING *base) const
   return global_var_ptr();
 }
 
+uchar *sys_var::session_var_ptr(THD *thd) const
+{
+  return ((uchar*)&(thd->variables)) + offset;
+}
+
 bool sys_var::check(THD *thd, set_var *var)
 {
   if (unlikely((var->value && do_check(thd, var)) ||
diff --git a/sql/set_var.h b/sql/set_var.h
index 2d538624825..cc279af5355 100644
--- a/sql/set_var.h
+++ b/sql/set_var.h
@@ -247,8 +247,7 @@ protected:
     Typically it's the same as session_value_ptr(), but it's different,
     for example, for ENUM, that is printed as a string, but stored as a number.
   */
-  uchar *session_var_ptr(THD *thd) const
-  { return ((uchar*)&(thd->variables)) + offset; }
+  uchar *session_var_ptr(THD *thd) const;
 
   uchar *global_var_ptr() const
   { return ((uchar*)&global_system_variables) + offset; }
diff --git a/sql/sql_explain.h b/sql/sql_explain.h
index bfd52290374..709ddd3f745 100644
--- a/sql/sql_explain.h
+++ b/sql/sql_explain.h
@@ -54,6 +54,8 @@ it into the slow query log.
 #ifndef SQL_EXPLAIN_INCLUDED
 #define SQL_EXPLAIN_INCLUDED
 
+class select_result_sink;
+
 class String_list: public List<char>
 {
 public:
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 2830e65a49e..bbfc8e0bf9b 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -12569,6 +12569,13 @@ inline void JOIN::eval_select_list_used_tables()
   }
 }
 
+JOIN_TAB *JOIN::get_sort_by_join_tab()
+{
+  return (need_tmp || !sort_by_table || skip_sort_order
+      || ((group || tmp_table_param.sum_func_count) && !group_list))
+            ? nullptr : join_tab+const_tables;
+}
+
 
 /*
   Determine {after which table we'll produce ordered set} 
@@ -13991,6 +13998,17 @@ bool JOIN_TAB::pfs_batch_update(JOIN *join)
          (!select_cond || !select_cond->with_subquery());               // 3
 }
 
+int st_join_table::get_non_merged_semijoin_select() const
+{
+  Item_in_subselect *subq;
+  if (table->pos_in_table_list &&
+      (subq= table->pos_in_table_list->jtbm_subselect))
+  {
+    return subq->unit->first_select()->select_number;
+  }
+  return 0; /* Not a merged semi-join */
+}
+
 
 /**
   Build a TABLE_REF structure for index lookup in the temporary table
@@ -30240,3 +30258,48 @@ static bool process_direct_rownum_comparison(THD *thd, SELECT_LEX_UNIT *unit,
 /**
   @} (end of group Query_Optimizer)
 */
+
+store_key::store_key_result store_key_item::copy_inner()
+{
+  TABLE *table= to_field->table;
+  MY_BITMAP *old_map= dbug_tmp_use_all_columns(table,
+                                               &table->write_set);
+  int res= FALSE;
+
+  /*
+    It looks like the next statement is needed only for a simplified
+    hash function over key values used now in BNLH join.
+    When the implementation of this function will be replaced for a proper
+    full version this statement probably should be removed.
+  */
+  to_field->reset();
+
+  if (use_value)
+     item->save_val(to_field);
+  else
+    res= item->save_in_field(to_field, 1);
+  /*
+   Item::save_in_field() may call Item::val_xxx(). And if this is a subquery
+   we need to check for errors executing it and react accordingly
+  */
+  if (!res && table->in_use->is_error())
+    res= 1; /* STORE_KEY_FATAL */
+  dbug_tmp_restore_column_map(&table->write_set, old_map);
+  null_key= to_field->is_null() || item->null_value;
+  return ((err != 0 || res < 0 || res > 2)
+        ? STORE_KEY_FATAL : (store_key_result) res);
+}
+
+store_key::store_key_result store_key::copy(THD *thd)
+{
+  enum store_key_result result;
+  enum_check_fields org_count_cuted_fields= thd->count_cuted_fields;
+  sql_mode_t org_sql_mode= thd->variables.sql_mode;
+  thd->variables.sql_mode&= ~(MODE_NO_ZERO_IN_DATE | MODE_NO_ZERO_DATE);
+  thd->variables.sql_mode|= MODE_INVALID_DATES;
+  thd->count_cuted_fields= CHECK_FIELD_IGNORE;
+  result= copy_inner();
+  thd->count_cuted_fields= org_count_cuted_fields;
+  thd->variables.sql_mode= org_sql_mode;
+  return result;
+}
diff --git a/sql/sql_select.h b/sql/sql_select.h
index d4e06f42249..ce8ee69ae3c 100644
--- a/sql/sql_select.h
+++ b/sql/sql_select.h
@@ -30,11 +30,17 @@
 
 #include "procedure.h"
 #include "sql_array.h"                        /* Array */
+#include "sql_class.h"
+#include "sql_lex.h"
 #include "records.h"                          /* READ_RECORD */
 #include "opt_range.h"                /* SQL_SELECT, QUICK_SELECT_I */
 #include "filesort.h"
 
-typedef struct st_join_table JOIN_TAB;
+class POSITION;
+#ifndef TMP_ENGINE_COLUMNDEF
+class TMP_ENGINE_COLUMNDEF;
+#endif
+
 /* Values in optimize */
 #define KEY_OPTIMIZE_EXISTS		1U
 #define KEY_OPTIMIZE_REF_OR_NULL	2U
@@ -199,6 +205,8 @@ enum join_type { JT_UNKNOWN,JT_SYSTEM,JT_CONST,JT_EQ_REF,JT_REF,JT_MAYBE_REF,
                  JT_HASH, JT_HASH_RANGE, JT_HASH_NEXT, JT_HASH_INDEX_MERGE};
 
 class JOIN;
+struct st_join_table;
+using JOIN_TAB= struct st_join_table;
 
 enum enum_nested_loop_state
 {
@@ -250,7 +258,7 @@ class Filesort;
 struct SplM_plan_info;
 class SplM_opt_info;
 
-typedef struct st_join_table {
+struct st_join_table {
   TABLE		*table;
   TABLE_LIST    *tab_list;
   KEYUSE	*keyuse;       /**< pointer to first used key */
@@ -649,16 +657,7 @@ typedef struct st_join_table {
     If this join_tab reads a non-merged semi-join (also called jtbm), return
     the select's number.  Otherwise, return 0.
   */
-  int get_non_merged_semijoin_select() const
-  {
-    Item_in_subselect *subq;
-    if (table->pos_in_table_list && 
-        (subq= table->pos_in_table_list->jtbm_subselect))
-    {
-      return subq->unit->first_select()->select_number;
-    }
-    return 0; /* Not a merged semi-join */
-  }
+  int get_non_merged_semijoin_select() const;
 
   bool access_from_tables_is_allowed(table_map used_tables,
                                      table_map sjm_lookup_tables)
@@ -686,7 +685,7 @@ typedef struct st_join_table {
                                         table_map remaining_tables);
   bool fix_splitting(SplM_plan_info *spl_plan, table_map remaining_tables,
                      bool is_const_table);
-} JOIN_TAB;
+};
 
 
 #include "sql_join_cache.h"
@@ -1663,12 +1662,7 @@ public:
     Return the table for which an index scan can be used to satisfy 
     the sort order needed by the ORDER BY/(implicit) GROUP BY clause 
   */
-  JOIN_TAB *get_sort_by_join_tab()
-  {
-    return (need_tmp || !sort_by_table || skip_sort_order ||
-            ((group || tmp_table_param.sum_func_count) && !group_list)) ?
-              NULL : join_tab+const_tables;
-  }
+  JOIN_TAB *get_sort_by_join_tab();
   bool setup_subquery_caches();
   bool shrink_join_buffers(JOIN_TAB *jt, 
                            ulonglong curr_space,
@@ -1839,19 +1833,7 @@ public:
     @details this function makes sure truncation warnings when preparing the
     key buffers don't end up as errors (because of an enclosing INSERT/UPDATE).
   */
-  enum store_key_result copy(THD *thd)
-  {
-    enum store_key_result result;
-    enum_check_fields org_count_cuted_fields= thd->count_cuted_fields;
-    sql_mode_t org_sql_mode= thd->variables.sql_mode;
-    thd->variables.sql_mode&= ~(MODE_NO_ZERO_IN_DATE | MODE_NO_ZERO_DATE);
-    thd->variables.sql_mode|= MODE_INVALID_DATES;
-    thd->count_cuted_fields= CHECK_FIELD_IGNORE;
-    result= copy_inner();
-    thd->count_cuted_fields= org_count_cuted_fields;
-    thd->variables.sql_mode= org_sql_mode;
-    return result;
-  }
+  enum store_key_result copy(THD *thd);
 
  protected:
   Field *to_field;				// Store data here
@@ -1937,36 +1919,7 @@ public:
   const char *name() const  override { return "func"; }
 
  protected:  
-  enum store_key_result copy_inner() override
-  {
-    TABLE *table= to_field->table;
-    MY_BITMAP *old_map= dbug_tmp_use_all_columns(table,
-                                                 &table->write_set);
-    int res= FALSE;
-
-    /* 
-      It looks like the next statement is needed only for a simplified
-      hash function over key values used now in BNLH join.
-      When the implementation of this function will be replaced for a proper
-      full version this statement probably should be removed.
-    */  
-    to_field->reset();
-
-    if (use_value)
-      item->save_val(to_field);
-    else
-      res= item->save_in_field(to_field, 1);
-    /*
-     Item::save_in_field() may call Item::val_xxx(). And if this is a subquery
-     we need to check for errors executing it and react accordingly
-    */
-    if (!res && table->in_use->is_error())
-      res= 1; /* STORE_KEY_FATAL */
-    dbug_tmp_restore_column_map(&table->write_set, old_map);
-    null_key= to_field->is_null() || item->null_value;
-    return ((err != 0 || res < 0 || res > 2) ? STORE_KEY_FATAL : 
-            (store_key_result) res);
-  }
+  enum store_key_result copy_inner() override;
 };
 
 
diff --git a/sql/sys_vars.cc b/sql/sys_vars.cc
index 7127cbc00f6..5c17f8a633e 100644
--- a/sql/sys_vars.cc
+++ b/sql/sys_vars.cc
@@ -6794,3 +6794,9 @@ static Sys_var_ulonglong Sys_max_rowid_filter_size(
        SESSION_VAR(max_rowid_filter_size), CMD_LINE(REQUIRED_ARG),
        VALID_RANGE(1024, (ulonglong)~(intptr)0), DEFAULT(128*1024),
        BLOCK_SIZE(1));
+
+bool Sys_var_mybool::session_update(THD *thd, set_var *var)
+{
+    session_var(thd, my_bool)= var->save_result.ulonglong_value != 0;
+    return false;
+}
diff --git a/sql/sys_vars.ic b/sql/sys_vars.ic
index 97e3a28b67e..47b2241d1a9 100644
--- a/sql/sys_vars.ic
+++ b/sql/sys_vars.ic
@@ -460,11 +460,7 @@ public:
     SYSVAR_ASSERT(getopt.arg_type == OPT_ARG || getopt.id < 0);
     SYSVAR_ASSERT(size == sizeof(my_bool));
   }
-  bool session_update(THD *thd, set_var *var)
-  {
-    session_var(thd, my_bool)= var->save_result.ulonglong_value != 0;
-    return false;
-  }
+  bool session_update(THD *thd, set_var *var);
   bool global_update(THD *thd, set_var *var)
   {
     global_var(my_bool)= var->save_result.ulonglong_value != 0;
diff --git a/unittest/sql/CMakeLists.txt b/unittest/sql/CMakeLists.txt
index 7dd0074eddb..f7367baa082 100644
--- a/unittest/sql/CMakeLists.txt
+++ b/unittest/sql/CMakeLists.txt
@@ -31,6 +31,7 @@ ADD_DEPENDENCIES(mf_iocache-t GenError)
 MY_ADD_TEST(mf_iocache)
 
 # Json writer needs String which needs sql library
-#ADD_EXECUTABLE(my_json_writer-t my_json_writer-t.cc dummy_builtins.cc)
-#TARGET_LINK_LIBRARIES(my_json_writer-t sql mytap)
-#MY_ADD_TEST(my_json_writer)
+ADD_EXECUTABLE(my_json_writer-t my_json_writer-t.cc dummy_builtins.cc)
+TARGET_LINK_LIBRARIES(my_json_writer-t PUBLIC sql mytap)
+TARGET_COMPILE_DEFINITIONS(my_json_writer-t PUBLIC JSON_WRITER_UNIT_TEST)
+MY_ADD_TEST(my_json_writer)
diff --git a/unittest/sql/my_json_writer-t.cc b/unittest/sql/my_json_writer-t.cc
index a585c17c75f..52988f7a979 100644
--- a/unittest/sql/my_json_writer-t.cc
+++ b/unittest/sql/my_json_writer-t.cc
@@ -26,7 +26,6 @@
 */
 
 struct TABLE;
-struct JOIN_TAB;
 class Json_writer;
 
 
@@ -39,13 +38,15 @@ public:
   Json_writer *get_current_json() { return nullptr; }
 };
 
-class THD 
+class THD
 {
 public:
   Opt_trace opt_trace;
 };
 
+#ifndef JSON_WRITER_UNIT_TEST
 #define JSON_WRITER_UNIT_TEST
+#endif
 #include "../sql/my_json_writer.h"
 #include "../sql/my_json_writer.cc"
 
@@ -124,19 +125,15 @@ int main(int args, char **argv)
     w.start_object();
     w.add_member("name").add_ll(1);
     w.add_member("name").add_ll(2);
-    w.end_object();
     ok(w.invalid_json, "JSON object member name collision");
   }
 
   {
     Json_writer w;
     w.start_object();
-    w.add_member("name").add_ll(1);
-    w.start_object();
+    w.add_member("name").start_object();
     w.add_member("name").add_ll(2);
-    w.end_object();
-    w.end_object();
-    ok(!w.invalid_json, "Valid JSON: nested object member name is the same");
+    ok(!w.invalid_json, "This must be valid JSON: nested object member has the same name");
   }
 
   diag("Done");