Unify profiling SHOW code and INFORMATION_SCHEMA code for

profiling.  Also,

Bug#26938: profiling client hang if used before enabled

In the SHOW command, not sending header data because we had no 
rows to send was a protocol violation.  Porting the SHOW PROFILE
command to use the Information Schema table avoids that problem.

mysql-test/r/profiling.result

+show profiles;
+Query_ID	Duration	Query
+show profile all;
+Status	Duration	CPU_user	CPU_system	Context_voluntary	Context_involuntary	Block_ops_in	Block_ops_out	Messages_sent	Messages_received	Page_faults_major	Page_faults_minor	Swaps	Source_function	Source_file	Source_line
 show session variables like 'profil%';
 Variable_name	Value
 profiling	OFF

mysql-test/t/profiling.test

+# Verify that the protocol isn't violated if we ask for profiling info
+# before profiling has recorded anything.
+show profiles;
+show profile all;
+
 # default is OFF
 show session variables like 'profil%';
 select @@profiling;

sql/sql_parse.cc

@@ -2315,6 +2315,15 @@ int prepare_schema_table(THD *thd, LEX *lex, Table_ident *table_ident,
       break;
     }
 #endif
+  case SCH_PROFILES:
+    /* 
+      Mark this current profiling record to be discarded.  We don't
+      wish to have SHOW commands show up in profiling.
+    */
+#ifdef ENABLED_PROFILING
+    thd->profiling.discard();
+#endif
+    break;
   case SCH_OPEN_TABLES:
   case SCH_VARIABLES:
   case SCH_STATUS:
@@ -2755,23 +2764,6 @@ mysql_execute_command(THD *thd)
 #else
     my_error(ER_FEATURE_DISABLED, MYF(0), "SHOW PROFILES", "enable-profiling");
     goto error;
-#endif
-    break;
-  }
-  case SQLCOM_SHOW_PROFILE:
-  {
-#ifdef ENABLED_PROFILING
-    thd->profiling.store();
-    thd->profiling.discard(); // will get re-enabled by reset()
-    if (lex->profile_query_id != 0)
-      res= thd->profiling.show(lex->profile_options, lex->profile_query_id);
-    else
-      res= thd->profiling.show_last(lex->profile_options);
-    if (res)
-      goto error;
-#else
-    my_error(ER_FEATURE_DISABLED, MYF(0), "SHOW PROFILE", "enable-profiling");
-    goto error;
 #endif
     break;
   }

sql/sql_profile.h

@@ -39,6 +39,7 @@ extern const char * const _unknown_func_;
 
 extern ST_FIELD_INFO query_profile_statistics_info[];
 int fill_query_profile_statistics_info(THD *thd, struct st_table_list *tables, Item *cond);
+int make_profile_table_for_show(THD *thd, ST_SCHEMA_TABLE *schema_table);
 
 
 #define PROFILE_NONE         0
@@ -332,12 +333,6 @@ public:
   /* SHOW PROFILES */
   bool show_profiles();
 
-  /* SHOW PROFILE FOR QUERY query_id */
-  bool show(uint options, uint profiling_query_id);
-
-  /* SHOW PROFILE */
-  bool show_last(uint options);
-
   /* ... from INFORMATION_SCHEMA.PROFILING ... */
   int fill_statistics_info(THD *thd, struct st_table_list *tables, Item *cond);
 };

sql/sql_show.cc

@@ -4344,7 +4344,8 @@ ST_SCHEMA_TABLE schema_tables[]=
   {"OPEN_TABLES", open_tables_fields_info, create_schema_table,
    fill_open_tables, make_old_format, 0, -1, -1, 1},
   {"PROFILING", query_profile_statistics_info, create_schema_table,
-    fill_query_profile_statistics_info, NULL, NULL, -1, -1, false},
+   fill_query_profile_statistics_info, make_profile_table_for_show, 
+   NULL, -1, -1, false},
   {"ROUTINES", proc_fields_info, create_schema_table, 
     fill_schema_proc, make_proc_old_format, 0, -1, -1, 0},
   {"SCHEMATA", schema_fields_info, create_schema_table,

sql/sql_yacc.yy

@@ -7044,7 +7044,13 @@ show_param:
         | PROFILES_SYM
           { Lex->sql_command = SQLCOM_SHOW_PROFILES; }
         | PROFILE_SYM opt_profile_defs opt_profile_args opt_limit_clause_init
-          { Lex->sql_command = SQLCOM_SHOW_PROFILE; }
+          { 
+            LEX *lex= Lex;
+            lex->sql_command= SQLCOM_SELECT;
+            lex->orig_sql_command= SQLCOM_SHOW_PROFILE;
+            if (prepare_schema_table(YYTHD, lex, NULL, SCH_PROFILES) != 0)
+              YYABORT;
+          }
         | opt_var_type STATUS_SYM wild_and_where
           {
             LEX *lex= Lex;

sql/table.h

@@ -320,7 +320,7 @@ enum enum_schema_tables
   SCH_COLUMN_PRIVILEGES,
   SCH_KEY_COLUMN_USAGE,
   SCH_OPEN_TABLES,
-  SCH_PROFILING,
+  SCH_PROFILES,
   SCH_PROCEDURES,
   SCH_SCHEMATA,
   SCH_SCHEMA_PRIVILEGES,