(This came up on IRC, but I'm not sure to what extent it should be considered a "bug")
If you do PQprepare(conn, "myfetch", "FETCH ALL FROM mycursor", ...); then the results are unpredictable in two ways: Firstly, nothing causes the plancache entry to be revalidated just because "mycursor" got opened with a different query, so the result type can change between uses. This could be considered a "caveat user" case, though, and I can't find anything that actually breaks. But the problem that actually came up is this: if you do the PQprepare before the named cursor has actually been opened, then everything works _up until_ the first event, such as a change to search_path, that forces a revalidation; and at that point it fails with the "must not change result type" error _even if_ the cursor always has exactly the same result type. This happens because the initial prepare actually stored NULL for plansource->resultDesc, since the cursor name wasn't found, while on the revalidate, when the cursor obviously does exist, it gets the actual result type. It seems a bit of a "gotcha" to have it fail in this case when the result type isn't actually being checked in other cases. (In the reported case, search_path was actually changing due to the creation of a temp table, so there was a certain amount of spooky-action-at-a-distance to figure out in order to locate the problem.) -- Andrew (irc:RhodiumToad) -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
