Fast default trigger and expand_tuple fixes

Andrew Dunstan <andrew@dunslane.net>

Commit: 9625ab79245b5b91162ede9d1b4d8b4be823c21c
Author: Andrew Dunstan <andrew@dunslane.net>
Date: 2018-09-24T20:20:08Z
Releases: 11.0
Fast default trigger and expand_tuple fixes

Ensure that triggers get properly filled in tuples for the OLD value.
Also fix the logic of detecting missing null values. The previous logic
failed to detect a missing null column before the first missing column
with a default. Fixing this has simplified the logic a bit.

Regression tests are added to test changes. This should ensure better
coverage of expand_tuple().

Original bug reports, and some code and test scripts from Tomas Vondra

Backpatch to release 11.

Files