Re: Page Scan Mode in Hash Index

Jesper Pedersen <jesper.pedersen@redhat.com>

From: Jesper Pedersen <jesper.pedersen@redhat.com>
To: Ashutosh Sharma <ashu.coek88@gmail.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2017-03-23T14:59:59Z
Lists: pgsql-hackers
Hi,

On 03/22/2017 09:32 AM, Ashutosh Sharma wrote:
> Done. Please refer to the attached v2 version of patch.
>

Thanks.

>>> 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().
>>>

0001v2:

In hashgettuple() you can remove the 'currItem' and 'offnum' from the 
'else' part, and do the assignment inside

   if (so->numKilled < MaxIndexTuplesPerPage)

instead.


No new comments for 0002 and 0003.

Best regards,
  Jesper



Commits

  1. Remove lsn from HashScanPosData.

  2. Fix trivial mistake in README.

  3. hash: Implement page-at-a-time scan.

  4. Reduce pinning and buffer content locking for btree scans.