I noticed the following code in src/backend/rewrite/rewriteDefine.c,
circa line 390:
/* * Are we converting a relation to a view? * * If so, check that the relation is empty because the
storage * for the relation is going to be deleted. Also insist that * the rel not have any triggers, indexes,
orchild tables. */ if (event_relation->rd_rel->relkind != RELKIND_VIEW) {
Under what circumstances do we "convert a relation to a view"? Is this
functionality exposed to the user?
Furthermore, it seems broken: it checks the pgclass.relhassubclass
attribute for this relation to see "if it has child tables", but this
is wrong, as relhassubclass only indicates that the relation MAY have
a subclass, not that is definitely does[1]. It also doesn't drop the
relation's TOAST table, if any, as the code itself notes.
-Neil
[1] This is because relhassubclass is not updated when a table's child
table is dropped, due to concurrency concerns; see has_subclass() in
plancat.c