Re: Page Scan Mode in Hash Index

Hi, Ashutosh!

I've assigned to review this patch.
At first, I'd like to notice that I like idea and general design.
Secondly, patch set don't apply cleanly to master. Please, rebase it.

On Tue, Feb 14, 2017 at 8:27 AM, Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com>
wrote:

> 1) 0001-Rewrite-hash-index-scans-to-work-a-page-at-a-time.patch: this
> patch rewrites the hash index scan module to work in page-at-a-time
> mode. It basically introduces two new functions-- _hash_readpage() and
> _hash_saveitem(). The former is used to load all the qualifying tuples
> from a target bucket or overflow page into an items array. The latter
> one is used by _hash_readpage to save all the qualifying tuples found
> in a page into an items array. Apart from that, this patch bascially
> cleans _hash_first(), _hash_next and hashgettuple().
>

I see that forward and backward scan cases of function _hash_readpage
contain a lot of code duplication
Could you please refactor this function to have less code duplication?

Also, I wonder if you have a special idea behind inserting data in test.sql
by 1002 separate SQL statements.
INSERT INTO con_hash_index_table (keycol) SELECT a FROM GENERATE_SERIES(1,
1000) a;

You can achieve the same result by execution of single SQL statement.
INSERT INTO con_hash_index_table (keycol) SELECT (a - 1) % 1000 + 1 FROM
GENERATE_SERIES(1, 1002000) a;
Unless you have some special idea of doing this in 1002 separate
transactions.

------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company