jing han wrote:
Hello,
I have questions about transaction and rollback.
Question 1:
In the postgresql.conf file of our running system,
autocommit=true. If leave it as true, can we disable
this attribute when we issue a connection to database?
From the DBD::Pg documentation:
The transaction behavior is now controlled with the attribute
AutoCommit. For a complete definition of AutoCommit
please refer to the DBI documentation.
According to the DBI specification the default for AutoCommit is TRUE.
In this mode, any change to the database
becomes valid immediately. Any ’begin’, ’commit’ or ’rollback’ statement
will be rejected.
If AutoCommit is switched-off, immediately a transaction will be started
by issuing a ’begin’ statement.
Any ’commit’ or ’rollback’ will start a new transaction. A disconnect
will issue a ’rollback’ statement.
Question 2:
If we use the following command to restore database.
system("su -l postgres -c \"psql -d dbname -f
/tmp/db_dump\"");
Can command psql rollback if in the middle of restore
power failure happens?
If the db_dump file starts with a transaction yes.
Question 3:
During restore, if power failure happens, we want to
rollback everything having been inserted or updated to
database. In another word, if we are restoring a
database with thousands of turples changes, at the
time, we restore the last turple, power failure
happens, we want to rollback. Can postgres support
huge data changes in one transaction block?
Yes.
How to
configure the limit of how much we can do in one
transaction block?
That would be controlled by issuing multiple transactions.
Hope to hear from you soon and thank you in advance.
Sincerely,
Joshua D. Drake
Best Regards
jing
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