According to the postgres 7 docs:
By default, Postgres executes transactions in unchained mode (also
known as “autocommit” in other database systems). In other words, each
user statement is executed in its own transaction and a commit is
implicitly performed at the end of the statement (if
Forest Wilkinson writes:
Does this mean that when I call a function I wrote, which is composed
of several queries, each of those queries will be executed in its own
transaction?
No
Or, will the statement containing the function call be executed in its
own transaction, thereby including