Heikki Linnakangas napsal(a):
Zdenek Kotala wrote:
Heikki Linnakangas napsal(a):
Besides, the "read all formats" approach wouldn't really avoid it
either. If you passed a toasted datum to a function, when the
function needs to detoast it, detoast_datum still wouldn't know
whether the datum is in old or new format. You'd still need to
detoast all values in the tuple somewhere before they could be passed
around.
If you look into pg_upgrade prototype patch I added page version
information into HeapTupleData structure. It keeps information about
format. All chunked data are stored on a pages with same page
versions. I think these two things are enough to have all necessary
information.
Functions are passed just a Datum, not HeapTupleData.
But executor works with HeapTupleData structure and it should convert it to the
new format before it passes it to function. My idea is to convert tuple in
ExecTupleStore or invent new node special for tuple conversion.
I expect that function cannot get toast pointer. It can get only detoasted
attributes. Correct me if I'm wrong.
Zdenek
--
Zdenek Kotala Sun Microsystems
Prague, Czech Republic http://sun.com/postgresql
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