Tom Lane wrote:
Joe Conway <[EMAIL PROTECTED]> writes:
I was actually just looking at that and ended up thinking that it might
be better to deal with it one level down in ExecProject (because it is
already passing targetlists directly to ExecTargetList).
I'd vote against that, because (a) ExecProject is used by all executor
node types, and we shouldn't add overhead to all of them for the benefit
of one; (b) ExecProject doesn't actually have any internal state at the
moment. To keep track of which targetlist to evaluate next, it would
not only need some internal state, it would have to be told the current
"es_direction". This stuff fits much better at the exec node level ---
again, I'd suggest looking at Append for a comparison.
OK.
But really the executor part of this is not the hard part; what we need
to think about first is what's the impact on the Query datastructure
that the parser/rewriter/planner use.
After a quick look, I think changing Query.targetList is too big an
impact, and probably unneeded given your suggestion below.
One of the problems with the current code is that the targetList in the
"VALUES..." case is being used for two purposes -- 1) to define the
column types, and 2) to hold the actual data. By putting the data into a
new node type, I think the targetList reverts to being just a list of
datatypes as it is with INSERT ... SELECT ...
I'm still liking the idea of pushing multi-values into a jointree node
type. Basically this would suggest representing "VALUES ..." as if it
were "SELECT * FROM VALUES ..." (which I believe is actually legal
syntax per spec) --- in the general case you'd need to have a Query node
that has a trivial "col1, col2, col3, ..." targetlist and then the
multiple values lists are in some kind of jointree entry. But possibly
this could be short-circuited somehow, at least for INSERT.
I'm liking this too. But when you say "jointree node", are you saying to
model the new node type after NestLoop/MergeJoin/HashJoin nodes? These
are referred to as "join nodes" in ExecInitNode. Or as you mentioned a
couple of times, should this look more like an Append node?
Thanks,
Joe
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