Re: COALESCE implementation question

At 22:27 5/08/00 -0400, Tom Lane wrote:
>Philip Warner <pjw@rhyme.com.au> writes:
>> explain update t1 set f1 = Coalesce( (select f2 from t2 x where x.f1 =
>> t1.f1), t1.f1);
>> NOTICE:  QUERY PLAN:
>
>> Seq Scan on t1  (cost=0.00..20.00 rows=1000 width=10)
>>   SubPlan
>>     -> Index Scan using t2f1 on t2 x  (cost=0.00..8.14 rows=10 width=4)
>>     -> Seq Scan on t2 x  (cost=0.00..22.50 rows=1000 width=4)
>
>This is a bug caused by interaction between two planning passes run
>on the same Query node.  The parser thinks it's cool to generate a
>CASE parsetree with multiple paths to the same sub-select Query node,
>but in fact it is not cool because planning destructively alters the
>Query node contents.  I'm amazed it didn't crash, to tell the truth.
>
>I have a patch but haven't applied it yet (been offline for most of
>two days due to telco idiocy :-().

Thanks for this; I must admit I was very surprised not to get a response
withing 24 hours! Is there any chance of sending me the patch - I have been
looking at the sources for a while now, and it would be nice to see the
answer...


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