Re: Add a filed to PageHeaderData

On Tue, Jun 24, 2014 at 3:40 PM, Kevin Grittner <kgrittn(at)ymail(dot)com> wrote:
>
> Soroosh Sardari <soroosh(dot)sardari(at)gmail(dot)com> wrote:
>
> > I check this problem with a virgin source code of
> > postgresql-9.3.2. So the bug is not for my codes.
>
> > By the way, following code has two different output and it is
> > weird.
>
> I can confirm that I see the difference in 9.3.2, and that I don't
> see the difference in 9.3.4. Upgrade.
>
> http://www.postgresql.org/support/versioning/
>
> There's really no point in reporting a possible bug on a version
> with known bugs which have already had fixes published.
>

FWIW I can reproduce this on HEAD with the attached patch. I could
reproduce this on a 64-bit Ubuntu as well as 64-bit Mac OSX. Very confusing
it is because I tried with various values for N in char[N] array and it
fails for N=20. Other values I tried are 4, 12, 22, 24 and the test passes
for all of them. The logic for trying other values is to see if pd_linp[]
starting on un-aligned boundary can trigger the issue. But there seem to be
no correlation.

postgres=# select version();

PostgreSQL 9.5devel on x86_64-apple-darwin13.2.0, compiled by Apple LLVM
version 5.1 (clang-503.0.38) (based on LLVM 3.4svn), 64-bit

postgres=# -- test SP-GiST index that's been built incrementally

postgres=# create table test_range_spgist(ir int4range);
postgres=# create index test_range_spgist_idx on test_range_spgist using
spgist (ir);
postgres=# insert into test_range_spgist select int4range(g, g+10) from
generate_series(1,586) g;
INSERT 0 586

postgres=# SET enable_seqscan = t;
postgres=# SET enable_indexscan = f;
postgres=# SET enable_bitmapscan = f;

postgres=# select * from test_range_spgist where ir -|- int4range(100,500);
ir
-----------
[90,100)
[500,510)
(2 rows)

postgres=# SET enable_seqscan = f;
postgres=# select * from test_range_spgist where ir -|- int4range(100,500);
ir
-----------
[90,100)
[500,510)
(2 rows)

At this point, both rows are visible via index scan as well as seq scan.

postgres=# insert into test_range_spgist select int4range(g, g+10) from
generate_series(587,587) g;
INSERT 0 1

postgres=# select * from test_range_spgist where ir -|- int4range(100,500);
ir
----------
[90,100)
(1 row)

Ouch. The second row somehow disappeared.

postgres=# SET enable_seqscan = t;
postgres=# select * from test_range_spgist where ir -|- int4range(100,500);
ir
-----------
[90,100)
[500,510)
(2 rows)

So the last INSERT suddenly makes one row disappear via the index scan
though its still reachable via seq scan. I tried looking at the SP-Gist
code but clearly I don't understand it a whole lot to figure out the issue,
if one exists.

Thanks,
Pavan

--
Pavan Deolasee
http://www.linkedin.com/in/pavandeolasee