Edit your postgresql.conf file to set the following:

log_statement = 'ddl'

Setting it to mod or all is also OK for this. Don't forget to reload the configuration:

/etc/init-d/postgresql reload

Now find all occurrences of the CREATE, ALTER, and DROP commands in the log:

postgres@hvost:~$ egrep -i "create|alter|drop" \ /var/log/postgresql/postgresql-9.4-main.log

If log rotation is in effect, you may need to use grep on older logs as well.

If the available logs are too new, and you haven't saved the older logs in some other place, you are out of luck.

The default settings in the postgresql.conf file for log rotation are as follows:

log_filename = 'postgresql-%Y-%m-%d_%H%M%S.log'
log_rotation_age = 1d
log_rotation_size = 10MB