Daniel

  1. set transaction level to repeatable read.

  2. create table in mysql and postgresql. create table repeatable_read (id integer primary key,text varchar(200));

  3. insert a new data in repeatable_read; insert into repeatable_read values(1,’first’);

  4. mysql | session 1 | session 2 | | — | — | | insert into repeatable_read values(1,’first’); | | | | select * from repeatable_read; result:(1,’first’) | | start transaction; | | | | start transaction; | | update repeatable_read set text = ‘second’ where id = 1; | | | select * from repeatable_read; result:(1,’second’) | select * from repeatable_read; result:(1,’first’) | | commit; | | | | update repeatable_read set text = ‘third’ where id = 1;| | select * from repeatable_read; result:(1,’second’) | select * from repeatable_read; result:(1,’third’) | | | commit; | | select * from repeatable_read; result:(1,’third’) | select * from repeatable_read; result:(1,’third’) |

  5. postgresql | session 1 | session 2 | | — | — | | insert into repeatable_read values(1,’first’); | | | | select * from repeatable_read; result:(1,’first’) | | begin; | | | | begin; | | update repeatable_read set text = ‘second’ where id = 1; | | | select * from repeatable_read; result:(1,’second’) | select * from repeatable_read; result:(1,’first’) | | commit; | | | | update repeatable_read set text = ‘third’ where id = 1; result: (ERROR: could not serialize access due to concurrent update)| | | update repeatable_read set text = ‘third’ where id = 1; result: (ERROR: current transaction is aborted, commands ignored until end of transaction block)| | select * from repeatable_read; result:(1,’second’) | select * from repeatable_read; result:(ERROR: current transaction is aborted, commands ignored until end of transaction block) | | | commit; result: (ROLLBACK) | | select * from repeatable_read; result:(1,’second’) | select * from repeatable_read; result:(1,’second’) |