Re: Examples required in || 5.10. Table Partitioning

Hello Bruce,

Apologies for late reply.
Thank you for acknowledging my email.

If I have any doubts regarding partition,indixing or query tuning in
feature may I email you?

Kind regards,
Tanay

On Sun, Mar 15, 2020, 1:12 AM Bruce Momjian <bruce(at)momjian(dot)us> wrote:

> On Thu, Feb 6, 2020 at 12:23:46PM +0000, PG Doc comments form wrote:
> > The following documentation comment has been logged on the website:
> >
> > Page: https://www.postgresql.org/docs/12/ddl-partitioning.html
> > Description:
> >
> > Hello ,
> >
> > As I'm searching for the official documentation of Hash Partition and
> List
> > Partition with example with more description the only information is
> found
> > is as below :
> >
> > List Partitioning
> > The table is partitioned by explicitly listing which key values appear in
> > each partition.
> >
> > Hash Partitioning
> > The table is partitioned by specifying a modulus and a remainder for each
> > partition. Each partition will hold the rows for which the hash value of
> the
> > partition key divided by the specified modulus will produce the specified
> > remainder.
> >
> > But how to create and manage these above 2 partition is not explained in
> > documentation properly officially.for further information related to
> these 2
> > partition we need to search private blogs,because of lack of information
> > provided in the documentation 5.10. Table Partitioning I only saw the
> Range
> > partition example throughout the Table Partitioning .
> >
> > I request you to modify the 5.10. Table Partitioning section and make it
> > more informative as Table Partition is very important in PostgreSQL .
>
> Well, there are examples in the CREATE TABLE manual page:
>
> https://www.postgresql.org/docs/12/sql-createtable.html
>
> When creating a hash partition, a modulus and remainder must be
> specified. The modulus must be a positive integer, and the
> remainder
> must be a non-negative integer less than the modulus. Typically,
> when
> initially setting up a hash-partitioned table, you should choose a
> modulus equal to the number of partitions and assign every table
> the
> same modulus and a different remainder (see examples, below).
> However,
> it is not required that every partition have the same modulus,
> only that
> every modulus which occurs among the partitions of a
> hash-partitioned
> table is a factor of the next larger modulus. This allows the
> number of
> partitions to be increased incrementally without needing to move
> all the
> data at once. For example, suppose you have a hash-partitioned
> table
> with 8 partitions, each of which has modulus 8, but find it
> necessary to
> increase the number of partitions to 16. You can detach one of the
> modulus-8 partitions, create two new modulus-16 partitions
> covering the
> same portion of the key space (one with a remainder equal to the
> remainder of the detached partition, and the other with a remainder
> equal to that value plus 8), and repopulate them with data. You
> can then
> repeat this -- perhaps at a later time -- for each modulus-8
> partition
> until none remain. While this may still involve a large amount of
> data
> movement at each step, it is still better than having to create a
> whole
> new table and move all the data at once.
>
> CREATE TABLE orders (
> order_id bigint not null,
> cust_id bigint not null,
> status text
> ) PARTITION BY HASH (order_id);
>
> CREATE TABLE orders_p1 PARTITION OF orders
> FOR VALUES WITH (MODULUS 4, REMAINDER 0);
> CREATE TABLE orders_p2 PARTITION OF orders
> FOR VALUES WITH (MODULUS 4, REMAINDER 1);
> CREATE TABLE orders_p3 PARTITION OF orders
> FOR VALUES WITH (MODULUS 4, REMAINDER 2);
> CREATE TABLE orders_p4 PARTITION OF orders
> FOR VALUES WITH (MODULUS 4, REMAINDER 3);
>
>
> CREATE TABLE cities (
> city_id bigserial not null,
> name text not null,
> population bigint
> ) PARTITION BY LIST (left(lower(name), 1));
>
> CREATE TABLE cities_ab
> PARTITION OF cities (
> CONSTRAINT city_id_nonzero CHECK (city_id != 0)
> ) FOR VALUES IN ('a', 'b');
>
> Is that sufficient?
>
> --
> Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
> EnterpriseDB https://enterprisedb.com
>
> + As you are, so once was I. As I am, so you will be. +
> + Ancient Roman grave inscription +
>