Re: [Postgres-xc-developers] Query Planning bug ?

[Ashutosh B. <ash...@en...>]

Hi Tomonari,
Can you please check the list's sanity before calling pgxc_collect_RTE()
and at every point in the minions of this function. My primary suspect is
the line pgxcplan.c:3094. We should copy the list before concatenating it.


On Wed, Jun 12, 2013 at 2:26 PM, Tomonari Katsumata <
kat...@po...> wrote:

> Hi Ashutosh,
>
> Thank you for the response.
>
> (2013/06/12 14:43), Ashutosh Bapat wrote:
>  >> Hi,
>  >> >
>  >> > I've investigated this problem(BUG:3614369).
>  >> >
>  >> > I caught the cause of it, but I can not
>  >> > find where to fix.
>  >> >
>  >> > The problem occurs when "pgxc_collect_RTE_walker" is called
> infinitely.
>  >> > It seems that rtable(List of RangeTable) become cyclic List.
>  >> > I'm not sure where the List is made.
>  >> >
>  >> >
>  > I guess, we are talking about EXECUTE DIRECT statement that you have
>  > mentioned earlier.
>
> Yes, that's right.
> I'm talking about EXECUTE DIRECT statement like below.
>   ---
>   EXECUTE DIRECT ON (data1) $$
>   SELECT
>   count(*)
>   FROM
>   (SELECT * FROM pg_locks l LEFT JOIN
>   (SELECT * FROM pg_stat_activity) s ON l.database = s.datid) a
>   $$
>   ---
>
>  > The function pgxc_collect_RTE_walker() is a recursive
>  > function. The condition to end the recursion is if the given node is
> NULL.
>  > We have to look at if that condition is met and if not why.
>  >
> I investigated it deeper, and I noticed that
> the infinitely loop happens at the function "range_table_walker()".
>
> Please see below trace.
> ===========================
> Breakpoint 1, range_table_walker (rtable=0x15e7968, walker=0x612c70
> <pgxc_collect_RTE_walker>, context=0x7fffd2de31c0,
>      flags=0) at nodeFuncs.c:1908
> 1908    in nodeFuncs.c
>
> (gdb) p *rtable
> $10 = {type = T_List, length = 5, head = 0x15e7998, tail = 0x15e9820}
> (gdb) p *rtable->head
> $11 = {data = {ptr_value = 0x15e79b8, int_value = 22968760, oid_value =
> 22968760}, next = 0x15e8190}
> (gdb) p *rtable->head->next
> $12 = {data = {ptr_value = 0x15e81b0, int_value = 22970800, oid_value =
> 22970800}, next = 0x15e8988}
> (gdb) p *rtable->head->next->next
> $13 = {data = {ptr_value = 0x15e89a8, int_value = 22972840, oid_value =
> 22972840}, next = 0x15e9018}
> (gdb) p *rtable->head->next->next->next
> $14 = {data = {ptr_value = 0x15e9038, int_value = 22974520, oid_value =
> 22974520}, next = 0x15e9820}
> (gdb) p *rtable->head->next->next->next->next
> $15 = {data = {ptr_value = 0x15e9840, int_value = 22976576, oid_value =
> 22976576}, next = 0x15e7998}
> ===========================
>
> The line which starts with "$15" has 0x15e7998 as its next data.
> But it is the head pointer(see the line which starts with $10).
>
> And in range_table_walker(), the function is called recursively.
> --------
> ...
>          if (!(flags & QTW_IGNORE_RANGE_TABLE))
>          {
>                  if (range_table_walker(query->rtable, walker, context,
> flags))
>                          return true;
>          }
> ...
> --------
>
> We should make rtable right or deal with "flags" properly.
> But I can't find where to do it...
>
> What do you think ?
>
> regards,
> ---------
> NTT Software Corporation
> Tomonari Katsumata
>
>
>
>
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-- 
Best Wishes,
Ashutosh Bapat
EntepriseDB Corporation
The Postgres Database Company