BUG#12427262 : 60961: SHOW TABLES VERY SLOW WHEN NOT IN SYSTEM DISK CACHE

Details:
- Merge : 5.1 -> 5.5
- Addded a new test case which was not added in 5.1 because PS was
  not there in 5.1.

mysql-test/r/bug12427262.result

+#
+# Bug#12427262 : 60961: SHOW TABLES VERY SLOW WHEN NOT IN SYSTEM DISK CACHE. 
+#
+create database show_table_db;
+use show_table_db;
+create table t1 (c1 int);
+create table t2 (c1 int);
+create table t3 (c1 int);
+create table t4 (c1 int);
+create table t5 (c1 int);
+create table t6 (c1 int);
+create table t7 (c1 int);
+create table t8 (c1 int);
+create table t9 (c1 int);
+create table t10 (c1 int);
+select Sum(ALL(COUNT_READ)) from performance_schema.file_summary_by_instance where FILE_NAME 
+like "%show_table_db/%.frm%" AND EVENT_NAME='wait/io/file/sql/FRM' into @count_read_before;
+show tables;
+Tables_in_show_table_db
+t1
+t10
+t2
+t3
+t4
+t5
+t6
+t7
+t8
+t9
+select Sum(ALL(COUNT_READ)) from performance_schema.file_summary_by_instance where FILE_NAME 
+like "%show_table_db/%.frm%" AND EVENT_NAME='wait/io/file/sql/FRM' into @count_read_after;
+select @count_read_after-@count_read_before;
+@count_read_after-@count_read_before
+0.000000000000000000000000000000
+show full tables;
+Tables_in_show_table_db	Table_type
+t1	BASE TABLE
+t10	BASE TABLE
+t2	BASE TABLE
+t3	BASE TABLE
+t4	BASE TABLE
+t5	BASE TABLE
+t6	BASE TABLE
+t7	BASE TABLE
+t8	BASE TABLE
+t9	BASE TABLE
+select Sum(ALL(COUNT_READ)) from performance_schema.file_summary_by_instance where FILE_NAME 
+like "%show_table_db/%.frm%" AND EVENT_NAME='wait/io/file/sql/FRM' into @count_read_after;
+select @count_read_after-@count_read_before;
+@count_read_after-@count_read_before
+10.000000000000000000000000000000
+drop table t1;
+drop database show_table_db;

mysql-test/t/bug12427262.test

+--echo #
+--echo # Bug#12427262 : 60961: SHOW TABLES VERY SLOW WHEN NOT IN SYSTEM DISK CACHE. 
+--echo #
+
+--source include/not_embedded.inc
+--source include/have_perfschema.inc
+
+--disable_warnings
+create database show_table_db;
+use show_table_db;
+create table t1 (c1 int);
+create table t2 (c1 int);
+create table t3 (c1 int);
+create table t4 (c1 int);
+create table t5 (c1 int);
+create table t6 (c1 int);
+create table t7 (c1 int);
+create table t8 (c1 int);
+create table t9 (c1 int);
+create table t10 (c1 int);
+--enable_warnings
+
+# Query PS to know initial read count for frm file.
+select Sum(ALL(COUNT_READ)) from performance_schema.file_summary_by_instance where FILE_NAME 
+like "%show_table_db/%.frm%" AND EVENT_NAME='wait/io/file/sql/FRM' into @count_read_before;
+
+show tables;
+
+# Query PS to know read count for frm file after above query. It should
+# not be changed as FRM file will not be opened for above query.
+select Sum(ALL(COUNT_READ)) from performance_schema.file_summary_by_instance where FILE_NAME 
+like "%show_table_db/%.frm%" AND EVENT_NAME='wait/io/file/sql/FRM' into @count_read_after;
+
+select @count_read_after-@count_read_before;
+
+show full tables;
+
+# Query PS to know read count for frm file after above query. COUNT_READ
+# will be incremented by 1 as FRM file will be opened for above query.
+select Sum(ALL(COUNT_READ)) from performance_schema.file_summary_by_instance where FILE_NAME 
+like "%show_table_db/%.frm%" AND EVENT_NAME='wait/io/file/sql/FRM' into @count_read_after;
+
+select @count_read_after-@count_read_before;
+
+--disable_warnings
+drop table t1;
+drop database show_table_db;
+--enable_warnings

sql/sql_show.cc

@@ -3192,8 +3192,12 @@ end:
 
 static int fill_schema_table_names(THD *thd, TABLE *table,
                                    LEX_STRING *db_name, LEX_STRING *table_name,
-                                   bool with_i_schema)
+                                   bool with_i_schema,
+                                   bool need_table_type)
 {
+  /* Avoid opening FRM files if table type is not needed. */
+  if (need_table_type)
+  {
     if (with_i_schema)
     {
       table->field[3]->store(STRING_WITH_LEN("SYSTEM VIEW"),
@@ -3227,6 +3231,7 @@ static int fill_schema_table_names(THD *thd, TABLE *table,
         return 0;
       }
     }
+  }
   if (schema_table_store_record(thd, table))
     return 1;
   return 0;
@@ -3763,7 +3768,8 @@ int get_all_tables(THD *thd, TABLE_LIST *tables, COND *cond)
           if (schema_table_idx == SCH_TABLE_NAMES)
           {
             if (fill_schema_table_names(thd, tables->table, db_name,
-                                        table_name, with_i_schema))
+                                        table_name, with_i_schema,
+                                        lex->verbose))
               continue;
           }
           else