Alexander Barkov added a comment - 2019-08-17 00:55 - edited Results of this change look good in many aspects. Code change made summary The old code made a really hard job on every INFORMATION_SCHEMA query: converted every ST_FIELD_INFO into Item then converted every new Item to Field then put every new Field into List<Field> and only after that called create_tmp_table() with the List<Field> The new code just creates a table directly from the array of ST_FIELD_INFO without such heavy conversion Unnecessary classes removed These classes were used only in I_S table creation, in the ST_FIELD_INFO->Item->Field chain: Item_return_date_time Item_blob After this change these classes were not needed any more, so they were removed. Note, it should be also easy to remove class Item_return_int (in a separate change). Creation of INFORMATION_SCHEMA tables is now faster I_S tables are now created directly from an array of ST_FIELD_INFO, no such heavy conversion involved any more. This example code runs 1% faster after the change: mysql --socket=/tmp/mysql.sock -s --database=test << QEND DELIMITER $$ CREATE OR REPLACE PROCEDURE p1() BEGIN FOR i IN 1..1000000 DO BEGIN SELECT * FROM INFORMATION_SCHEMA.COLUMNS LIMIT 0; END ; END FOR ; END ; $$ DELIMITER ; QEND   time mysql --socket=/tmp/mysql.sock -s --database=test --execute="CALL p1()" The code is now data type friendly I_S columns of new data types now work out of the box, without a need of new wrapper classes like the former Item_blob, Item_return_date_time or Item_return_int. A new data type developer just needs to override Type_handler_xxx::create_schema_field(), which is one line method with a single new Field_xxx() statement. User defined plugins are now able to have fields of their own data type in their pluggable INFORMATION_SCHEMA tables. We'll be adding built-in SQL standard data types soon, such as TIMESTAMP WITH TIME ZONE, INTERVAL, so adding I_S columns of these types is also trivial. It's now easy to extend creating of temporary tables The new class Create_tmp_table now understands two input data formats: List<Item> ST_SCHEMA_TABLE Adding new formats is now trivial and does not need heavy conversion like ST_FIELD_INFO->Item->Field. One just needs to add a proper add_fields() method. Examples: it's now trivial to create a temporary table directly from List<Item>. Currently we convert List<Item> into List<Field> in such cases. Direct table creation from List<Item> can make the code faster. On ALTER, we convert every Field into Create_field. Such conversion is not really needed. We could create an altered table from a mixture of old Fields with new Create_fields, which would improve performance.