> Sorry for long delay. Here is more or less what I had in mind. After changing
> read_closest to read the whole page I couldn't resist to just merge it into
> readpage itself, since it's basically the same. It could raise questions about>
> performance and how intrusive this patch is, but I hope it's not that much of a
> problem (in the worst case we can split it back). I've also added few tests for
> the issue you've mentioned. Thanks again, I'm appreciate how much efforts you
> put into reviewing!
Putting it into one function makes sense I think. Looking at the patch, I think in general there are some good improvements in there.
I'm afraid I did manage to find another incorrect query result though, having to do with the keepPrev part and skipping to the first tuple on an index page:
postgres=# drop table if exists b; create table b as select a,b::int2 b,(b%2)::int2 c from generate_series(1,5) a, generate_series(1,366) b; create index on b (a,b,c); analyze b;
DROP TABLE
SELECT 1830
CREATE INDEX
ANALYZE
postgres=# set enable_indexskipscan=1;
SET
postgres=# select distinct on (a) a,b,c from b where b>=1 and c=0 order by a,b;
a | b | c
---+---+---
1 | 2 | 0
2 | 4 | 0
3 | 4 | 0
4 | 4 | 0
5 | 4 | 0
(5 rows)
postgres=# set enable_indexskipscan=0;
SET
postgres=# select distinct on (a) a,b,c from b where b>=1 and c=0 order by a,b;
a | b | c
---+---+---
1 | 2 | 0
2 | 2 | 0
3 | 2 | 0
4 | 2 | 0
5 | 2 | 0
(5 rows)
