HeapTupleHeaderGetRawCommandId will give you what’s in the header whether
it is useful or not. Most code should use HeapTupleHeaderGetCmin or
HeapTupleHeaderGetCmax instead, but note that those Assert that you can
get a legitimate result, ie you are in the originating transaction!
How many attributes does the specified [HeapTupleHeader
] have?
HeapTupleHeaderGetRawXmin returns the “raw” xmin field, which is the xid
originally used to insert the tuple. However, the tuple might actually
be frozen (via HeapTupleHeaderSetXminFrozen) in which case the tuple’s xmin
is visible to every snapshot. Prior to PostgreSQL 9.4, we actually changed
the xmin to FrozenTransactionId, and that value may still be encountered
on disk.
Safety
Safety
Safety
Does the specified [HeapTuple
] (tup
) contain nulls?
Extract an attribute of a heap tuple and return it as a Datum.
This works for either system or user attributes. The given attnum
is properly range-checked.