On 2016/02/04 21:57, Ashutosh Bapat wrote:

    One more: I think the following in postgresGetForeignJoinPaths() is
    a good idea, but I think it's okay to just check whether
    root->rowMarks is non-NIL, because that since we have rowmarks for
    all base relations except the target, if we have
    root->parse->commandType==CMD_DELETE (or
    root->parse->commandType==CMD_UPDATE), then there would be at least
    one non-target base relation in the joinrel, which would have a rowmark.


Sorry, I am unable to understand it fully. But what you are suggesting
that if there are root->rowMarks, then we are sure that there is at
least one base relation apart from the target, which needs locking rows.
Even if we don't have one, still changes in a row of target relation
after it was scanned, can result in firing EPQ check, which would need
the local plan to be executed, thus even if root->rowMarks is NIL, EPQ
check can fire and we will need alternate local plan.

Yeah, I think that is true, but if root->rowMarks==NIL, we won't have non-target foreign tables, and therefore postgresGetForeignJoinPaths() will never be called. No?

Best regards,
Etsuro Fujita




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