Re: [GENERAL] GIN Indexes: Extensibility

[Anton Ananich]

Paul,

This is a really valuable idea. It will work in some situations for me. But in 
other situations I do not know if table will have a key of type int[] or 
string[] or even mixed. That’s why I’d wish to use JSON arrays and customize 
sort ordering.

Anyway I appreciate you shared this approach!
Regards,
Anthony Ananich
http://ananich.pro

On Jul 27, 2016, at 18:00, Paul Jungwirth  wrote:

> On 07/27/2016 07:44 AM, Vick Khera wrote:
>> On Wed, Jul 27, 2016 at 3:28 AM, Anton Ananich  
>> wrote:
>>> In my situation this order is invalid. Obviously, year 2016 should go after
>>> 2014, like that:
>> 
>> I think you expect JSONB to sort differently than it does. I cannot
>> imagine what a "natural" ordering of arbitrary JSON objects is.
> 
> FWIW, Postgres arrays do sort in the way he's expecting:
> 
> paul=# create table t (id integer, v integer[]);
> CREATE TABLE
> paul=# insert into t values (1, array[2014]), (2, array[2014, 1]), (3, 
> array[2016]);
> INSERT 0 3
> paul=# select * from t order by v;
> id |v
> +--
>  1 | {2014}
>  2 | {2014,1}
>  3 | {2016}
> (3 rows)
> 
> So maybe convert to an array before sorting?
> 
> Paul
> 
> 
> 
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Re: [GENERAL] GIN Indexes: Extensibility

[Anton Ananich]

Vick, you are right. That’s why I’d wish to add some custom code to MY 
PostgreSQL instance and set such a sort order, which is optimal for my 
application.

On Jul 27, 2016, at 17:44, Vick Khera  wrote:

> On Wed, Jul 27, 2016 at 3:28 AM, Anton Ananich  
> wrote:
>> In my situation this order is invalid. Obviously, year 2016 should go after
>> 2014, like that:
> 
> I think you expect JSONB to sort differently than it does. I cannot
> imagine what a "natural" ordering of arbitrary JSON objects is.
> 
> 
> -- 
> Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
> To make changes to your subscription:
> http://www.postgresql.org/mailpref/pgsql-general



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Re: [GENERAL] GIN Indexes: Extensibility

[Paul Jungwirth]

On 07/27/2016 07:44 AM, Vick Khera wrote:

On Wed, Jul 27, 2016 at 3:28 AM, Anton Ananich  wrote:

In my situation this order is invalid. Obviously, year 2016 should go after
2014, like that:


I think you expect JSONB to sort differently than it does. I cannot
imagine what a "natural" ordering of arbitrary JSON objects is.


FWIW, Postgres arrays do sort in the way he's expecting:

paul=# create table t (id integer, v integer[]);
CREATE TABLE
paul=# insert into t values (1, array[2014]), (2, array[2014, 1]), (3, 
array[2016]);

INSERT 0 3
paul=# select * from t order by v;
 id |v
+--
  1 | {2014}
  2 | {2014,1}
  3 | {2016}
(3 rows)

So maybe convert to an array before sorting?

Paul



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Re: [GENERAL] GIN Indexes: Extensibility

[Vick Khera]

On Wed, Jul 27, 2016 at 3:28 AM, Anton Ananich  wrote:
> In my situation this order is invalid. Obviously, year 2016 should go after
> 2014, like that:

I think you expect JSONB to sort differently than it does. I cannot
imagine what a "natural" ordering of arbitrary JSON objects is.


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[GENERAL] GIN Indexes: Extensibility

[Anton Ananich]

Dear All,

Here is what I have:

user=# create table FOO (key jsonb);
CREATE TABLE
user=# insert into FOO(key) values ('[2014]'), ('[2015]'), ('[2016]'), ('[2014, 
2]'), ('[2014, 2, 3]'), ('[2014, 3]'), ('[2014,2,4]'), ('[2014, 2,4]'), 
('[2014,3,13]'), ('[2014, 2, 15]');
INSERT 0 10
user=# SELECT key FROM FOO order by key;
  key  
---
 [2014]
 [2015] <==
 [2016] <==
 [2014, 2]
 [2014, 3] <==
 [2014, 2, 3]
 [2014, 2, 4]
 [2014, 2, 4]
 [2014, 2, 15]
 [2014, 3, 13]
(10 rows)


In my situation this order is invalid. Obviously, year 2016 should go after 
2014, like that:

  key  
---
 [2014]
 [2014, 2]
 [2014, 2, 3]
 [2014, 2, 4]
 [2014, 2, 4]
 [2014, 2, 15]
 [2014, 3] <==
 [2014, 3, 13]
 [2015] <==
 [2016] <==

This is a simplified example, my real application is much more complicated and 
sorted arrays could have tens of values, could even be arrays of arrays.For 
this reason I need to customize sort function.

I found that there is a way to customize function `int compare(Datum a, Datum 
b)` (proof link: 
https://www.postgresql.org/docs/9.5/static/gin-extensibility.html), but I found 
no example which shows how to use it.

I’d appreciate any information which could help me to achieve the described 
result, even if it is just a link to an existing example.

Regards,
Anthony Ananich