Horton

Re: Partition-wise join for join between (declaratively) partitioned tables

Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>

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From: Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>, Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp>, Thomas Munro <thomas.munro@enterprisedb.com>, Rafia Sabih <rafia.sabih@enterprisedb.com>, Rajkumar Raghuwanshi <rajkumar.raghuwanshi@enterprisedb.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2017-10-05T17:03:30Z
Lists: pgsql-hackers 
On Thu, Oct 5, 2017 at 7:18 PM, Alvaro Herrera <alvherre@2ndquadrant.com> wrote:
> Robert Haas wrote:
>
>> Regarding nomenclature and my previous griping about wisdom, I was
>> wondering about just calling this a "partition join" like you have in
>> the regression test.  So the GUC would be enable_partition_join, you'd
>> have generate_partition_join_paths(), etc.  Basically just delete
>> "wise" throughout.
>
> If I understand correctly, what's being used here is the "-wise" suffix,
> unrelated to wisdom, which Merriam Webster lists as "adverb combining
> form" here https://www.merriam-webster.com/dictionary/wise (though you
> have to scroll down a lot), which is defined as
>
> 1 a :in the manner of  * crabwise * fanwise
>   b :in the position or direction of  * slantwise * clockwise
> 2 :with regard to :in respect of * dollarwise
>

That's right.

> According to that, the right way to write this is "partitionwise join"
> (no dash), which means "join in respect of partitions", "join with
> regard to partitions".

Google lists mostly  "partition wise" or "partition-wise" and very
rarely "partitionwise". The first being used in other DBMS literature.
The paper (there aren't many on this subject) I referred [1] uses
"partition-wise". It made more sense to replace " " or "-" with "_"
when syntax doesn't allow the first two. I am not against
"partitionwise" but I don't see any real reason why we should move
away from popular usage of this term.

[1] https://users.cs.duke.edu/~shivnath/papers/sigmod295-herodotou.pdf

-- 
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company

Commits

  1. Add test for partitionwise join involving default partition.

  2. Rewrite the code that applies scan/join targets to paths.

  3. Fix code related to partitioning schemes for dropped columns.

  4. Copy information from the relcache instead of pointing to it.

  5. Basic partition-wise join functionality.

  6. Associate partitioning information with each RelOptInfo.

  7. Expand partitioned table RTEs level by level, without flattening.

  8. Set partitioned_rels appropriately when UNION ALL is used.

  9. Remove dedicated B-tree root-split record types.

  10. Assorted preparatory refactoring for partition-wise join.

  11. Teach adjust_appendrel_attrs(_multilevel) to do multiple translations.

  12. Avoid unnecessary single-child Append nodes.

  13. Revisit handling of UNION ALL subqueries with non-Var output columns.