Обсуждение: Performance on JSONB select

select * from MyTable where
  ((JsonBField->>'status'='descartada' and
To_Date(JsonBField->'descartada'->>'data','yyyy-mm-dd') > Current_Date) or
   (JsonBField->>'status'='contrato' and
To_Date(JsonBField->'contrato'->>'data','yyyy-mm-dd') > Current_Date-7) or
   (JsonBField->>'status'='naoatribuido'));

Considering this table has a million records, I would like to use a proper
index, but how can I use an index when using operator >. 




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ok, my select performed better but I had to create 8 indices to speed up my
query.

I would love to create just one index using GIN(JsonBField jsonb_ops) but
using version 11 I cannot use operators like > and  <. 

I see on docs that version 12 has jsonpath Filter Expression Elements and
they include > and <. So, the question is, will be possible to have just one
index and use it with "jsonpath Filter Expression Elements ?



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Greetings,

* Michael Lewis (mlewis@entrata.com) wrote:
> Much of indexing strategy depends on knowing the data like how many
> distinct values and what the distribution is like. Is JsonBField->>'status'
> always set? Are those three values mentioned in this query common or rare?
> Can you re-write this query to avoid using an OR in the where clause? Are
> you just wanting to add a GIN index for the jsonb paths? Or do you want
> indexed like below that are a bit stylized to this query?

If you know a field is going to always be there, you're better off, by
far, by just having a regular column for that value and a straight up
btree for it.  This saves a significant amount of space and makes it
much easier to index and work with.

Thanks,

Stephen

I think I solved my problem. I didn´t know it was possible but I´ve created
an almost dynamic index, because it´ll index for status and corresponding
datevalue of an object with that status value.

Postgres, I love you.

Just one B-Tree index with 2 fields, Status and DateTime of that respective
Status object. My Json has always a status and a respective object of that
status with other values. So I know if it has that status it has a Date
Value or not on its correspondent object.

{
    "status": "visitadescartada",
    "contrato": {},
    "atribuido": {"datevalue": "2019-09-05 14:47:11.149095-03"},
    "trabalhando": {},
    "visitaagendada": {"datevalue": "2019-09-05
15:06:24.255548-03","caption": "Agendado"},
    "visitadescartada": {"datevalue": "2019-09-12
11:47:17.45782-03","caption": "Desagendado"},
    "digitacaodescartada": {}
}

create index IndexByStatusAndDate on MyTable (
(JsonBField->>$$status$$),
castimmutabletimestamp(JsonBField->(JsonBField->>$$status$$)->>'datevalue'))
where (JsonBField ? $$status$$);

select * from MyTable where (JsonBField ? $$status$$) and
case when JsonBField->>$$status$$=$$cadastrodescartado$$ then
castimmutabletimestamp(JsonBField->(JsonBField->>$$status$$)->>'datevalue')
> castimmutabletimestamp($$2019-10-01$$)
     when JsonBField->>$$status$$=$$visitadescartada$$ then
castimmutabletimestamp(JsonBField->(JsonBField->>$$status$$)->>'datevalue')
> castimmutabletimestamp($$2019-10-01$$)
     when JsonBField->>$$status$$=$$contrato$$ then
castimmutabletimestamp(funilvendas->(JsonBField->>$$status$$)->>'data') >
castimmutabletimestamp($$2019-10-01$$)
     when JsonBField->>$$status$$=$$naoatribuido$$ then True end;

And performance now is great because I´m using both fields on index.



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I think I solved my problem. I didn´t know it was possible but I´ve created
an almost dynamic index, because it´ll index for status and corresponding
datevalue of an object with that status value.

Postgres, I love you.

Just one B-Tree index with 2 fields, Status and DateTime of that respective
Status object. My Json has always a status and a respective object of that
status with other values. So I know if it has that status it has a Date
Value or not on its correspondent object.

{
    "status": "visitadescartada",
    "contrato": {},
    "atribuido": {"datevalue": "2019-09-05 14:47:11.149095-03"},
    "trabalhando": {},
    "visitaagendada": {"datevalue": "2019-09-05
15:06:24.255548-03","caption": "Agendado"},
    "visitadescartada": {"datevalue": "2019-09-12
11:47:17.45782-03","caption": "Desagendado"},
    "digitacaodescartada": {}
}

create index IndexByStatusAndDate on MyTable (
(JsonBField->>$$status$$),
castimmutabletimestamp(JsonBField->(JsonBField->>$$status$$)->>'datevalue'))
where (JsonBField ? $$status$$);

select * from MyTable where (JsonBField ? $$status$$) and
case when JsonBField->>$$status$$=$$cadastrodescartado$$ then
castimmutabletimestamp(JsonBField->(JsonBField->>$$status$$)->>'datevalue')
> castimmutabletimestamp($$2019-10-01$$)
     when JsonBField->>$$status$$=$$visitadescartada$$ then
castimmutabletimestamp(JsonBField->(JsonBField->>$$status$$)->>'datevalue')
> castimmutabletimestamp($$2019-10-01$$)
     when JsonBField->>$$status$$=$$contrato$$ then
castimmutabletimestamp(JsonBField->(JsonBField->>$$status$$)->>'data') >
castimmutabletimestamp($$2019-10-01$$)
     when JsonBField->>$$status$$=$$naoatribuido$$ then True end;

And performance now is great because I´m using both fields on index.




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I told it was almost dynamic because it uses DateValue from an object or
another, depending on value of staus key.



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No, no, no, partial index is the where clause of it and I´m not talking about that.
I´m talking about datevalue, which will be used one or another, depending on status value

This record iindex will be status and datevalue from "visitadescartada" object
{
  "status": "visitadescartada",
  "atribuido": {"datevalue": "2019-09-05 14:47:11"},
  "visitadescartada": {"datevalue": "2019-09-12 11:47:17"},
  "digitacaodescartada": {}
}

And here the index record will be status and datevalue from "atribuido" object
{
  "status": "atribuido",
  "atribuido": {"datevalue": "2019-09-05 14:47:11"},
  "visitadescartada": {"datevalue": "2019-09-12 11:47:17"},
  "digitacaodescartada": {}
}

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Sent from the PostgreSQL - general mailing list archive at Nabble.com.

Sorry, I told you that the status was always populated but not, I need that
filter for the index because not all records are using that json structure.
When json is not null then yes, Status is always there. 
I have maybe 20 or 25% of records having json populated, so, I really need
that filter.

Yes, that solution is fine. Selectivity is fine, speed is fine and the index
is "almost dynamic"



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