Horton

Re: [POC] hash partitioning

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>
Cc: amul sul <sulamul@gmail.com>, Yugo Nagata <nagata@sraoss.co.jp>, David Steele <david@pgmasters.net>, Greg Stark <stark@mit.edu>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2017-05-16T17:23:13Z
Lists: pgsql-hackers 
On Tue, May 16, 2017 at 3:19 AM, Ashutosh Bapat
<ashutosh.bapat@enterprisedb.com> wrote:
> While earlier, I thought the same, I am wondering whether this is
> true. Don't different collations deem different strings equal e.g one
> collation may deem 'aa' and 'AA' as same but other may not.

No, that's not allowed.  This has been discussed many times on this
mailing list.  See varstr_cmp(), which you will notice refuses to
return 0 unless the strings are bytewise identical.

> Or is that
> encoding problem being discussed in hash functions thread?

No, that's something else entirely.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Commits

  1. Refactor get_partition_for_tuple a bit.

  2. Adopt Bob Jenkins' improved hash function for hash_any(). This changes the

  3. Improve hash_any() to use word-wide fetches when hashing suitably aligned