Re: [POC] hash partitioning

On Tue, May 16, 2017 at 4:22 PM, amul sul <sulamul(at)gmail(dot)com> wrote:
> v6 patch has bug in partition oid mapping and indexing, fixed in the
> attached version.
>
> Now partition oids will be arranged in the ascending order of hash
> partition bound (i.e. modulus and remainder sorting order)

Thanks for the update patch. I have some more comments.

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+ if (spec->remainder < 0)
+ ereport(ERROR,
+ (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
+ errmsg("hash partition remainder must be less than modulus")));

I think this error message is not correct, you might want to change it
to "hash partition remainder must be non-negative integer"

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+ The table is partitioned by specifying remainder and modulus for each
+ partition. Each partition holds rows for which the hash value of

Wouldn't it be better to say "modulus and remainder" instead of
"remainder and modulus" then it will be consistent?

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+ An <command>UPDATE</> that causes a row to move from one partition to
+ another fails, because

fails, because -> fails because

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Wouldn't it be a good idea to document how to increase the number of
hash partitions, I think we can document it somewhere with an example,
something like Robert explained upthread?

create table foo (a integer, b text) partition by hash (a);
create table foo1 partition of foo with (modulus 2, remainder 0);
create table foo2 partition of foo with (modulus 2, remainder 1);

You can detach foo1, create two new partitions with modulus 4 and
remainders 0 and 2, and move the data over from the old partition

I think it will be good information for a user to have? or it's
already documented and I missed it?

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--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com