Horton

Re: [POC] hash partitioning

Amul Sul <sulamul@gmail.com>

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From: amul sul <sulamul@gmail.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>, Jesper Pedersen <jesper.pedersen@redhat.com>, Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>, Thom Brown <thom@linux.com>, Dilip Kumar <dilipbalaut@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: 2017-11-02T08:15:22Z
Lists: pgsql-hackers 
On Thu, Nov 2, 2017 at 1:35 PM, Robert Haas <robertmhaas@gmail.com> wrote:
> On Wed, Nov 1, 2017 at 3:46 PM, amul sul <sulamul@gmail.com> wrote:
>> Although partition constraints become more simple, there isn't any performance
>> gain with 0005 patch. Also I am little skeptic about logic in 0005 where we
>> copied extended hash function info from the partition key, what if parent is
>> changed while we are using it? Do we need to keep lock on parent until commit in
>> satisfies_hash_partition?
>
> I don't think it should be possible for the parent to be changed.  I
> mean, the partition key is altogether immutable -- it can't be changed
> after creation time.  The partition bounds can be changed for
> individual partitions but that would require a lock on the partition.
>
> Can you give an example of the kind of scenario about which you are concerned?
>

Yes, you are correct, column involved in the partitioning are immutable.

I was just worried about any change in the partition key column that
might change selected hash function.

Regards,
Amul

Commits

  1. Add hash partitioning.

  2. Add sanity check for pg_proc.provariadic

  3. Add hash_combine64.

  4. Make RelationGetPartitionDispatchInfo expand depth-first.

  5. Introduce 64-bit hash functions with a 64-bit seed.

  6. pg_dump: Add a --load-via-partition-root option.