On Wed, Oct 14, 2020 at 6:04 PM Heikki Linnakangas <[email protected]> wrote:
I'll continue with the last couple of patches in this thread.
I committed the move of the cross-partition logic to new
ExecCrossPartitionUpdate() function, with just minor comment editing and
pgindent. I left out the refactoring around the calls to AFTER ROW
INSERT/DELETE triggers. I stared at the change for a while, and wasn't
sure if I liked the patched or the unpatched new version better, so I
left it alone.
Looking at the last patch, "Revise child-to-root tuple conversion map
management", that's certainly an improvement. However, I find it
confusing that sometimes the mapping from child to root is in
relinfo->ri_ChildToRootMap, and sometimes in
relinfo->ri_PartitionInfo->pi_PartitionToRootMap. When is each of those
filled in? If both are set, is it well defined which one is initialized
first?
In general, I'm pretty confused by the initialization of
ri_PartitionInfo. Where is initialized, and when? In execnodes.h, the
definition of ResultRelInfo says:
/* info for partition tuple routing (NULL if not set up yet) */
struct PartitionRoutingInfo *ri_PartitionInfo;
That implies that the field is initialized lazily. But in
ExecFindPartition, we have this:
if (partidx == partdesc->boundinfo->default_index)
{
PartitionRoutingInfo *partrouteinfo =
rri->ri_PartitionInfo;
/*
* The tuple must match the partition's layout for the
constraint
* expression to be evaluated successfully. If the
partition is
* sub-partitioned, that would already be the case due
to the code
* above, but for a leaf partition the tuple still
matches the
* parent's layout.
*
* Note that we have a map to convert from root to
current
* partition, but not from immediate parent to current
partition.
* So if we have to convert, do it from the root slot;
if not, use
* the root slot as-is.
*/
if (partrouteinfo)
{
TupleConversionMap *map =
partrouteinfo->pi_RootToPartitionMap;
if (map)
slot =
execute_attr_map_slot(map->attrMap, rootslot,
partrouteinfo->pi_PartitionTupleSlot);
else
slot = rootslot;
}
ExecPartitionCheck(rri, slot, estate, true);
}
That check implies that it's not just lazily initialized, the code will
work differently if ri_PartitionInfo is set or not.
I think all this would be more clear if ri_PartitionInfo and
ri_ChildToRootMap were both truly lazily initialized, the first time
they're needed. And if we removed
ri_PartitionInfo->pi_PartitionToRootMap, and always used
ri_ChildToRootMap for it.
Maybe remove PartitionRoutingInfo struct altogether, and just move its
fields directly to ResultRelInfo.
- Heikki
