Re: Add SPLIT PARTITION/MERGE PARTITIONS commands

On Tue, May 31, 2022 at 1:43 PM Zhihong Yu <zyu(at)yugabyte(dot)com> wrote:

>
>
> On Tue, May 31, 2022 at 12:43 PM Dmitry Koval <d(dot)koval(at)postgrespro(dot)ru>
> wrote:
>
>> >Just out of curiosity, why is SPLIT / MERGE support not included for
>> >HASH partitions? Because sibling partitions can have a different
>> >modulus, you should be able to e.g. split a partition with (modulus,
>> >remainder) of (3, 1) into two partitions with (mod, rem) of (6, 1) and
>> >(6, 4) respectively, with the reverse being true for merge operations,
>> >right?
>>
>> You are right, SPLIT/MERGE operations can be added for HASH-partitioning
>> in the future. But HASH-partitioning is rarer than RANGE- and
>> LIST-partitioning and I decided to skip it in the first step.
>> Maybe community will say that SPLIT/MERGE commands are not needed... (At
>> first step I would like to make sure that it is no true)
>>
>> P.S. I attached patch with 1-line warning fix (for cfbot).
>> --
>> With best regards,
>> Dmitry Koval
>>
>> Postgres Professional: http://postgrespro.com
>
>
> Hi,
> For attachPartTable, the parameter wqueue is missing from comment.
> The parameters of CloneRowTriggersToPartition are called parent
> and partition. I think it is better to name the parameters to
> attachPartTable in a similar manner.
>
> For struct SplitPartContext, SplitPartitionContext would be better name.
>
> + /* Store partition contect into list. */
> contect -> context
>
> Cheers
>
Hi,
For transformPartitionCmdForMerge(), nested loop is used to detect
duplicate names.
If the number of partitions in partcmd->partlist, we should utilize map to
speed up the check.

For check_parent_values_in_new_partitions():

+ if (!find_value_in_new_partitions(&key->partsupfunc[0],
+ key->partcollation, parts,
nparts, datum, false))
+ found = false;

It seems we can break out of the loop when found is false.

Cheers