MDEV-6388: ANALYZE $stmt output in the slow query log

Make log_slow_verbosity=explain actually print ANALYZE (that
is, EXPLAIN otuput with two extra columns).

sql/log.cc

@@ -2951,7 +2951,7 @@ bool MYSQL_QUERY_LOG::write(THD *thd, time_t current_time,
     {
       StringBuffer<128> buf;
       DBUG_ASSERT(!thd->free_list);
-      if (!print_explain_query(thd->lex, thd, &buf))
+      if (!print_explain_for_slow_log(thd->lex, thd, &buf))
         my_b_printf(&log_file, "%s", buf.c_ptr_safe());
       thd->free_items();
     }

sql/sql_class.cc

@@ -2367,10 +2367,10 @@ CHANGED_TABLE_LIST* THD::changed_table_dup(const char *key, long key_length)
 }
 
 
-int THD::send_explain_fields(select_result *result)
+int THD::send_explain_fields(select_result *result, uint8 explain_flags, bool is_analyze)
 {
   List<Item> field_list;
-  make_explain_field_list(field_list);
+  make_explain_field_list(field_list, explain_flags, is_analyze);
   result->prepare(field_list, NULL);
   return (result->send_result_set_metadata(field_list,
                                            Protocol::SEND_NUM_ROWS | 
@@ -2386,7 +2386,8 @@ int THD::send_explain_fields(select_result *result)
   Explain_query::print_explain and co.
 */
 
-void THD::make_explain_field_list(List<Item> &field_list)
+void THD::make_explain_field_list(List<Item> &field_list, uint8 explain_flags,
+                                  bool is_analyze)
 {
   Item *item;
   CHARSET_INFO *cs= system_charset_info;
@@ -2395,7 +2396,7 @@ void THD::make_explain_field_list(List<Item> &field_list)
   field_list.push_back(new Item_empty_string("select_type", 19, cs));
   field_list.push_back(item= new Item_empty_string("table", NAME_CHAR_LEN, cs));
   item->maybe_null= 1;
-  if (lex->describe & DESCRIBE_PARTITIONS)
+  if (explain_flags & DESCRIBE_PARTITIONS)
   {
     /* Maximum length of string that make_used_partitions_str() can produce */
     item= new Item_empty_string("partitions", MAX_PARTITIONS * (1 + FN_LEN),
@@ -2419,20 +2420,20 @@ void THD::make_explain_field_list(List<Item> &field_list)
   item->maybe_null=1;
   field_list.push_back(item= new Item_return_int("rows", 10,
                                                  MYSQL_TYPE_LONGLONG));
-  if (lex->analyze_stmt)
+  if (is_analyze)
   {
     field_list.push_back(item= new Item_return_int("r_rows", 10,
                                                    MYSQL_TYPE_LONGLONG));
     item->maybe_null=1;
   }
 
-  if (lex->analyze_stmt || lex->describe & DESCRIBE_EXTENDED)
+  if (is_analyze || (explain_flags & DESCRIBE_EXTENDED))
   {
     field_list.push_back(item= new Item_float("filtered", 0.1234, 2, 4));
     item->maybe_null=1;
   }
 
-  if (lex->analyze_stmt)
+  if (is_analyze)
   {
     field_list.push_back(item= new Item_float("r_filtered", 0.1234, 2, 4));
     item->maybe_null=1;

sql/sql_class.h

@@ -3083,8 +3083,10 @@ class THD :public Statement,
   void add_changed_table(TABLE *table);
   void add_changed_table(const char *key, long key_length);
   CHANGED_TABLE_LIST * changed_table_dup(const char *key, long key_length);
-  int send_explain_fields(select_result *result);
-  void make_explain_field_list(List<Item> &field_list);
+  int send_explain_fields(select_result *result, uint8 explain_flags,
+                          bool is_analyze);
+  void make_explain_field_list(List<Item> &field_list, uint8 explain_flags,
+                               bool is_analyze);
   /**
     Clear the current error, if any.
     We do not clear is_fatal_error or is_fatal_sub_stmt_error since we

sql/sql_explain.cc

@@ -136,7 +136,7 @@ int Explain_query::send_explain(THD *thd)
   LEX *lex= thd->lex;
  
   if (!(result= new select_send()) || 
-      thd->send_explain_fields(result))
+      thd->send_explain_fields(result, lex->describe, lex->analyze_stmt))
     return 1;
 
   int res;
@@ -177,9 +177,9 @@ int Explain_query::print_explain(select_result_sink *output,
 }
 
 
-bool print_explain_query(LEX *lex, THD *thd, String *str)
+bool print_explain_for_slow_log(LEX *lex, THD *thd, String *str)
 {
-  return lex->explain->print_explain_str(thd, str, false);
+  return lex->explain->print_explain_str(thd, str, /*is_analyze*/ true);
 }
 
 
@@ -190,7 +190,7 @@ bool print_explain_query(LEX *lex, THD *thd, String *str)
 bool Explain_query::print_explain_str(THD *thd, String *out_str,  bool is_analyze)
 {
   List<Item> fields;
-  thd->make_explain_field_list(fields);
+  thd->make_explain_field_list(fields, thd->lex->describe, is_analyze);
 
   select_result_text_buffer output_buf(thd);
   output_buf.send_result_set_metadata(fields, thd->lex->describe);

sql/sql_lex.h

@@ -541,7 +541,7 @@ class Explain_query;
 void delete_explain_query(LEX *lex);
 void create_explain_query(LEX *lex, MEM_ROOT *mem_root);
 void create_explain_query_if_not_exists(LEX *lex, MEM_ROOT *mem_root);
-bool print_explain_query(LEX *lex, THD *thd, String *str);
+bool print_explain_for_slow_log(LEX *lex, THD *thd, String *str);
 
 class st_select_lex_unit: public st_select_lex_node {
 protected:

sql/sql_parse.cc

@@ -5618,7 +5618,7 @@ static bool execute_sqlcom_select(THD *thd, TABLE_LIST *all_tables)
       */
       if (!(result= new select_send()))
         return 1;                               /* purecov: inspected */
-      thd->send_explain_fields(result);
+      thd->send_explain_fields(result, lex->describe, lex->analyze_stmt);
         
       /*
         This will call optimize() for all parts of query. The query plan is