> select * from t1 where name = somename ? == equality match // if yes, hash
> partitioning may be helpful to a have reasonably balanced distribution
yes, its an equality check,
On Friday, May 21, 2021, 12:08:25 PM PDT, Vijaykumar Jain
<vijaykumarjain.git...@gmail.com> wrote:
just out of curiosity,what would a typical query be ?
select * from t1 where name = somename ? == equality match // if yes, hash
partitioning may be helpful to a have reasonably balanced distributionorselect
* from t1 where name like 'some%'; ---- what would be the distribution of
rows for such queries. i mean it can return 1 row or all rows or anything in
between.
that may result in unbalanced partitioning.
then why partition at all ? 2B rows,
if i go with 100KB size per row. that would be around 200GB.
also, queries may benefit from trigram matching.Index Columns for `LIKE` in
PostgreSQL | Niall Burkley's Developer Blog
On Fri, 21 May 2021 at 22:08, Nagaraj Raj <nagaraj...@yahoo.com> wrote:
Hi David,
Hi,
I am trying to create partitions on the table which have around 2BIL records
and users will always look for the "name", its not possible to create a
partition with a list, so we are trying to create a partition-based first
letter of the name column. name column has a combination of alpha numeric
values.
> postgres=# select chr(ascii('z')+1) ;
> chr
> -----
> {
> (1 row)
I tried as below, I'm able to create a partition table for 'Z', but it's not
identifying partition table.
postgres=# select chr(ascii('Z')+1) ;
chr
-----
[
(1 row)
create table mytable_z of mytable for values from ('Z') to ('Z[');CREATE
TABLE
insert into mytable values(4,'ZAR83NB');
ERROR: no partition of relation "mytable" found for rowDETAIL: Partition key of
the failing row contains (name) = (ZAR83NB).SQL state: 23514
On Friday, May 21, 2021, 01:24:13 AM PDT, David Rowley
<dgrowle...@gmail.com> wrote:
On Fri, 21 May 2021 at 19:02, Nagaraj Raj <nagaraj...@yahoo.com> wrote:
> then what would be the range of Z
> FROM (Z) to (?) ;
postgres=# select chr(ascii('z')+1) ;
chr
-----
{
(1 row)
> same way for 9
postgres=# select chr(ascii('9')+1) ;
chr
-----
:
(1 row)
https://en.wikipedia.org/wiki/ASCII
You can also use MINVALUE and MAXVALUE to mean unbounded at either end
of the range.
But is there a particular need that you want to partition this way? It
seems like it might be a bit painful to maintain, especially if you're
not limiting yourself to ASCII or ANSI characters.
You might want to consider HASH partitioning if you're just looking
for a way to keep your tables and indexes to a more manageable size.
You've not really mentioned your use case here, so it's hard to give
any advice.
There are more details about partitioning in
https://www.postgresql.org/docs/current/ddl-partitioning.html
David
--
Thanks,VijayMumbai, India
