Re: Postgres 11, partitioning with a custom hash function

On 4 October 2018 at 16:22, Harry B <harrysungod@gmail.com> wrote:
> I am still having trouble reconciling what happens under the HASH
> partitioning!. If I have text column forming the basis of PARTITIONED BY
> HASH, the HASH value used in the partitioning setup does not seem to match
> to `hashtext()` of that value

It won't match. The hash partition hash is seeded with a special const
(HASH_PARTITION_SEED) see [1].

You could likely roll your own hash ops. See [2] for an example. This
can then be used to create a hash partitioned table like [3].

[1] https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/backend/partitioning/partbounds.c#l2056
[2] https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/test/regress/sql/insert.sql#l241
[3] https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/test/regress/sql/hash_part.sql#l10

-- 
 David Rowley                   http://www.2ndQuadrant.com/
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