When browsing the HISTORY file for 7.4.2 I discovered the following:
[...] A dump/restore is not required for those running 7.4.X. However, it may be advisable as the easiest method of incorporating fixes for two errors that have been found in the initial contents of 7.4.X system catalogs. A dump/initdb/reload sequence using 7.4.2's initdb will automatically correct these problems. [...]
The HISTORY file documents how to manually fix the problems without a dump/initdb/reload.
Oliver Elphick, the Debian Pg package maintainer informs me that if you were running the 7.4.1 Debian package before, the 7.4.2 package does NOT automatically install these fixes.
