On Thu, Nov 18, 2021 at 12:59:03PM -0500, Melanie Plageman wrote: > On Mon, Nov 8, 2021 at 3:13 PM Justin Pryzby <pry...@telsasoft.com> wrote: > > On Mon, Nov 08, 2021 at 02:52:28PM -0500, Melanie Plageman wrote: > > > On Tue, Nov 2, 2021 at 4:23 PM Justin Pryzby <pry...@telsasoft.com> wrote: > > > > > > > > Several places have a conditional value for the first argument > > > > (randomAccess), > > > > but your patch changes the behavior to a constant "true". I didn't > > > > review the > > > > patch beyond that. > > > > ... > > > I believe the patch has preserved the same behavior. All of the callers > > > for which I replaced tuplestore_begin_heap() which passed a variable for > > > the randomAccess parameter had set that variable to something which was > > > effectively the same as passing true -- SFRM_Materialize_Random. > > > > I don't think so ? > > > > They callers aren't passing SFRM_Materialize_Random, but rather > > (allowedModes & SFRM_Materialize_Random) != 0 > > > > Where allowedModes is determined EXEC_FLAG_BACKWARD. ... > You are right. I misread it. > > So, I've attached a patch where randomAccess is now an additional > parameter (and registered for the next fest). > > I was thinking about how to add a test that would have broken when I > passed true for randomAccess to tuplestore_begin_heap() when false was > required. But, I don't fully understand the problem. If backward > accesses to a tuplestore are not allowed but randomAccess is mistakenly > passed as true, would the potential result be potentially wrong results > from accessing the tuplestore results backwards?
No, see here src/backend/utils/fmgr/README-The Tuplestore must be created with randomAccess = true if src/backend/utils/fmgr/README:SFRM_Materialize_Random is set in allowedModes, but it can (and preferably src/backend/utils/fmgr/README-should) be created with randomAccess = false if not. Callers that can support src/backend/utils/fmgr/README-both ValuePerCall and Materialize mode will set SFRM_Materialize_Preferred, src/backend/utils/fmgr/README-or not, depending on which mode they prefer. If you use "randomAccess=true" when it's not needed, the result might be less efficient. Some callers specify "true" when they don't need to. I ran into that here. https://www.postgresql.org/message-id/21724.1583955...@sss.pgh.pa.us Maybe you'd want to add an 0002 patch which changes those to conditional ? BTW, there should be a newline before MakeFuncResultTuplestore(). -- Justin
