Itagaki Takahiro <[email protected]> writes:
> On Thu, Oct 21, 2010 at 2:18 PM, Tom Lane <[email protected]> wrote:
>> The plan for UNION initially involves a couple of SubqueryScan nodes,
>> which impose an extra cost of cpu_tuple_cost per tuple. Â Those later
>> get optimized away, but we don't try to readjust the cost estimates
>> for that.
> Thanks. It also explains my another question why Merge Append cannot
> be used for UNION ALL plans.
Hmm, seems like the example you show ought to work. I wonder if there
was an oversight in that patch...
regards, tom lane
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