In circumstances where locking a table or a row in one table while fetching
data into one or more other tables, it is important to avoid unwanted cancellation
of the initial transaction in case something goes wrong in one of the secondary
query. This kind of situation is often related to update of records by user
during the interaction, the user triggers widgets leading to other data
Example with customer data editing: you present customer data and the user
edit the address, he enters a erroneous zip code and you present a list
of valid zip codes. Doing this means executing another select on your zip
code table. This may lead to executing SQL code conflicting with the fact
that we are inside a transaction. This situation is solved by executing
the secondary queries from another PostgreSQL connection object.
The easiest way to get another connection object to the same database is
to clone the first one.
This is the purpose of
What does this method is really give you a NEW connection to the back-end.
This new connection is independent of the first one but with exactly the
same characteristics (login, database, options).
Another circumstance where cloning a connection object may be required
is when processing result from a SELECT query needs to UPDATE another table.
You could use -(PgSQLResult *)getResultSet; but this routine copy the data
from the back-end into the client memory. If the result is huge, this may
lead to performance hit. If you clone the connection object and execute
the UPDATE thru this new connection, There is no need to fetch the whole
result of the first query and you may process each row at the time in a
Note that each PosgreSQL connection object created
should be released by calling
so that it's returned to the internal connection pool.