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Tom Lane 37507962c3 Handle unexpected query results, especially NULLs, safely in connectby(). ... connectby() didn't adequately check that the constructed SQL query returns what it's expected to; in fact, since commit 08c33c426b it wasn't checking that at all. This could result in a null-pointer-dereference crash if the constructed query returns only one column instead of the expected two. Less excitingly, it could also result in surprising data conversion failures if the constructed query returned values that were not I/O-conversion-compatible with the types specified by the query calling connectby(). In all branches, insist that the query return at least two columns; this seems like a minimal sanity check that can't break any reasonable use-cases. In HEAD, insist that the constructed query return the types specified by the outer query, including checking for typmod incompatibility, which the code never did even before it got broken. This is to hide the fact that the implementation does a conversion to text and back; someday we might want to improve that. In back branches, leave that alone, since adding a type check in a minor release is more likely to break things than make people happy. Type inconsistencies will continue to work so long as the actual type and declared type are I/O representation compatible, and otherwise will fail the same way they used to. Also, in all branches, be on guard for NULL results from the constructed query, which formerly would cause null-pointer dereference crashes. We now print the row with the NULL but don't recurse down from it. In passing, get rid of the rather pointless idea that build_tuplestore_recursively() should return the same tuplestore that's passed to it. Michael Paquier, adjusted somewhat by me		11 years ago
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tablefunc.sql	Handle unexpected query results, especially NULLs, safely in connectby().	11 years ago