Re: Add SPLIT PARTITION/MERGE PARTITIONS commands - Mailing list pgsql-hackers

From Zhihong Yu
Subject Re: Add SPLIT PARTITION/MERGE PARTITIONS commands
Date
Msg-id CALNJ-vRsNi5bNy2M8BU+oPOimqm5J2ZU6HK_w1SnhGu8mT99yg@mail.gmail.com
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In response to Re: Add SPLIT PARTITION/MERGE PARTITIONS commands  (Zhihong Yu <zyu@yugabyte.com>)
List pgsql-hackers


On Tue, May 31, 2022 at 1:43 PM Zhihong Yu <zyu@yugabyte.com> wrote:


On Tue, May 31, 2022 at 12:43 PM Dmitry Koval <d.koval@postgrespro.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

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