Re: Adding skip scan (including MDAM style range skip scan) to nbtree

On Tue, Mar 18, 2025 at 9:37 AM Alena Rybakina
<a(dot)rybakina(at)postgrespro(dot)ru> wrote:
> Sorry, I figured it out. The Assert was added to avoid misuse of the function to reinitialize memory and to ensure that it happens when parallel_aware is positive.

Yeah. The assertion is supposed to suggest "don't worry, I didn't
forget to test parallel_aware in this function
[ExecIndexScanReInitializeDSM or ExecIndexScanReInitializeDSM], it's
just that I expect to not be called unless parallel_aware is true".

An alternative approach would have been to explicitly handle
parallel_aware=false in ExecIndexScanReInitializeDSM and
ExecIndexScanReInitializeDSM: they could just return false. That would
make ExecIndexScanReInitializeDSM and ExecIndexScanReInitializeDSM
more consistent with other nearby functions (in nodeIndexScan.c and
nodeIndexOnlyScan.c), at the cost of making the calling code (in
execParallel.c) less consistent. I really don't think that that
alternative is any better to what I actually did (I actually
considered doing things this way myself at one point), though it also
doesn't seem worse. So I'm inclined to do nothing about it now.

--
Peter Geoghegan