What is the safest way to access/modify the pg_class attribute
and still avoid any race conditions with the other backends ?

A specific example is: To solve the CREATE INDEX problem with
HOT, I am thinking of adding (along with other things) a pg_class
boolean attribute, say hot_update_enable. All backends are
supposed to check this attribute before they perform an UPDATE.
The attribute would usually be available in relation->rd_rel

My understanding is that the backend which sets this attribute
must first acquire a lock on the heap relation of sufficient
strength so as to ensure that there are no concurrent UPDATErs,
update the pg_class row and then release the lock on the relation.
This would ensure that no backend has a stale "Relation"
pointer with stale value of hot_update_enable.

Also, should I use heap_inplace_update() rather than
simple_heap_update() because I want other backends to see the
change immediately irrespective of their snapshot ?

Is this a fair analysis ? Are there any rules I must follow
to avoid any deadlock and race conditions. I know we should
not be requesting a higher grade lock while holding a
lower grade lock, but are there any other restrictions/best
practices ?



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