Re: Questions about HeapTupleHeaderData

Zdenek Kotala  writes:
> If I understand correctly then for read path (select) tuple is always 
> HeapTuple, because we need support select xmax ... And DatumTuple is 
> used for write path (insert/update) and it is "converted" to HeapTuple 
> in heap_insert/heap_update function.

No, DatumTuple is used for any free-standing composite-type Datum.
Thinking about it as "write path" and "read path" seems to me to
be missing the mark entirely.  In general most tuple-reading code
is supposed to work with either.
		regards, tom lane