Hi,
Maybe my test case is wrong and possibly also my understanding of BufFile.
There is some ambiguity about what interXact=true really means.
Current code documentations for bufFileCreateTemp says:
* If interXact is true, the temp file will not be automatically deleted
* at end of transaction.
*
* Note: if interXact is true, the caller had better be calling us in a
* memory context, and with a resource owner, that will survive across
* transaction boundaries.
buffile.c headers also say:
* BufFile also supports temporary files that can be used by the single
backend
* when the corresponding files need to be survived across the
transaction and
* need to be opened and closed multiple times. Such files need to be created
* as a member of a FileSet.
I don't know what this means for a BufFile created with interXact=True and is
not a FileSet.
The only use case I have found in in tuplestore_puttuple_common:
/*
* We switch out of the state->context as this is a generation
* context, which isn't ideal for allocations relating to the
* BufFile.
*/
oldcxt = MemoryContextSwitchTo(state->context->parent);
state->myfile = BufFileCreateTemp(state->interXact);
MemoryContextSwitchTo(oldcxt);
CurrentResourceOwner = oldowner;
This seems to be used by cursors declared with HOLD.
I agree with your patch because as far as I understand interXact=true keeps
temp file open
and does not mean bufFileClose is called several time for the same temp file.
Le 17/08/2026 à 08:01, Sergey Soloviev a écrit :
Hi!
Thanks for response.
I do not know whether this is correct to throw error when we can not
do it.
'temp_file_limit' is enforced for actually created files and not on
BufFile, so
if we can create one without it's associated file, then I see here no
problems.
And this must be true for both normal and inter-xact, because in that
case
owner backend is the only who can work with the file, so there is no need
to forcibly create disk file.
Hello
I think there is an issue with this patch: you are not taking into
account a inter-transaction BufFile.
If a BufFile is created with isInterXact set to true, BufFileClose
does not flush data and this looks wrong.
You can test this with the following extension
https://github.com/pierreforstmann/buffile .
With PostgreSQL 20devdel, I get:
--
-- Test BufFileClose() flushing behavior.
--
CREATE EXTENSION buffile;
-- A regular temporary BufFile should not be flushed by BufFileClose().
--
-- With temp_file_limit = 0, a physical write must fail. Therefore
-- false means that BufFileClose() did not attempt the write.
SET temp_file_limit = 0;
SELECT test_buffile_temp(false);
INFO: BufFileClose has not flushed data
test_buffile_temp
-------------------
f
(1 row)
-- An inter-transaction BufFile must still be flushed by BufFileClose().
--
-- Therefore the physical write should fail with temp_file_limit = 0.
SELECT test_buffile_temp(true);
INFO: BufFileClose has not flushed data
test_buffile_temp
-------------------
f
(1 row)
RESET temp_file_limit;
-- A FileSet BufFile must also be flushed by BufFileClose(), because
-- another opener must be able to see its contents.
SELECT test_buffile_fileset();
INFO: BufFileClose has flushed data
test_buffile_fileset
----------------------
t
(1 row)
Regards
Pierre Forstmann
---
Sergey Soloviev
TantorLabs: https://tantorlabs.com
