is it ok to rename a parent table from which partitioned child tables are based ?
For example if I have
CREATE TABLE demos_qa (
demo_id int,
demo_date VARCHAR,
demo_text TEXT)
PARTITION BY RANGE (trxn_post_dt);
CREATE TABLE demos_2022 PARTITION OF demos_qa
FOR VALUES FROM ('2022-01-01') TO ('2023-01-01');
CREATE TABLE demos_2021 PARTITION OF demos_qa
FOR VALUES FROM ('2021-01-01') TO ('2022-01-01');
CREATE TABLE demos_2020 PARTITION OF demos_qa
FOR VALUES FROM ('2020-01-01') TO ('2021-01-01');
and I bulk load the partition tables.
I now want to rename the parent table from demo_qa to demo. Can I do that and will things work as normal without having to change the definitions of the partition tables ?
Yes, this will work.
The partitions won't be renamed though, in case you expected that.
Related
I have a postgres table set up with a list partition defined on a column like so:
create table table1 (
val varchar(10),
t_type varchar(10)
) partition by list(t_type);
create table table1_xvals partition of table1 for values in ('xval1','xval2');
create table table1_yvals partition of table1 for values in ('yval1','yval2');
As I insert data into table1, and I can see the size of the table and individual partitions increasing, however when I try to select data from any of those tables, nothing shows up (select * from ). Is there anything wrong with how I'm creating the tables or selecting data?
That is normal. You are loading the data in a single database transaction, and the effects of a database transaction only become visible when the transaction is completed (committed). If you are loading the data with a single INSERT or COPY statement, the transaction will end as soon as the statement is done.
I would like to shift data from a specific paritioned table of parent to separate table.Can someone suggest what's the better way.
If I create a table
CREATE TABLE parent columns(a,b,c)partition by c
c Type is DATE.
CREATE TABLE dec_partition PARTITION OF parent FOR VALUES FROM '2021-02-12' to 2021-03-12;
Now I want to copy table dec_partition to separate table in single command with least time.
NOTE: The table has around 4million rows with 20 columns (1 of the column is in jsonb)
I have a postgres table (in postgres12) which is supposed to have thousands of partitions (200k at least) in near future.
Here is how I am creating the parent table:
create table if not exists content (
key varchar(20) not NULL,
value json not null default '[]'::json
) PARTITION BY LIST(key)
And then adding any given child tables like:
create table if not exists content_123 PARTITION OF content for VALUES in ('123');
Also I am adding an index on top of the child table for quick access (since I will be accessing the child table directly):
create index if not exists content_123_idx on content_123 using btree(key)
Here is my question: I have never in the past managed this many partitions in a postgres table so I am just wondering is there any downside of doing what I am doing? Also, (as mentioned above) I will not be querying from the parent table directly, but will read directly from individual child tables.
With these table definitions, the index is completely useless.
With 200000 partitions, query planning will become intolerably slow, and each SQL statement will need very many locks and open files. This won't work well.
Lump several keys together into a single partition (then the index might make sense).
Is there any problem when creating partitions of a table which has got seqence (nextval) as one of its field in postgresql 12?
Regards,
Seenu.
If you define a bigserial or identity column in a partitioned table, all partitions you create will share the same sequence. Consequently, auto-generated values will be unique across the whole partitioned table.
I am trying to ALTER a table to use partitions LIST in postgres 11. I have been trying for hours but i keep getting errors.
I have a huge table, clients, with ( client_id, customer_id, value).
I have already created a new empty table, clients, by renaming the old table to clients_old and then created the new table with: CREATE TABLE clients( like clients_old including all).
And from here I am stuck when trying to add the LIST partition.
I have tried to:
ALTER TABLE Clients attach PARTITION BY LIST (client_id) --> fail;
ALTER TABLE Clients attach PARTITION LIST (client_id) --> fail;
ALTER TABLE Clients ADD PARTITION LIST (client_id) --> fail;
What syntax should I use to alter the table to use partitions?
Quote from the manual
It is not possible to turn a regular table into a partitioned table or vice versa
So, you can not change an existing non-partitioned table to a partitioned table.
You need to create a new table (with a different name) that is partitioned, create all necessary partitions and then copy the data from the old table to the new, partitioned table.
Something like:
create table clients_partitioned
(
.... all columns ...
)
PARTITION BY LIST (client_id);
Then create the partitions:
create table clients_1
partition of clients_partioned
for values in (1,2,3);
create table clients_1
partition of clients_partioned
for values in (4,5,6);
Then copy the data:
insert into clients_partitioned
select *
from clients;
Once that is done, you can drop the old table and rename the new table:
drop table clients;
alter table clients_partitioned rename to clients;
Don't forget to re-create your foreign keys and indexes.
I had to add for tag in order to add the partition:
create table clients_1
partition of clients_partioned
for values in (4,5,6);
because without for was a syntax error.