Re: [GENERAL] json aggregation question

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От Yasin Sari
Тема Re: [GENERAL] json aggregation question
Дата
Msg-id CADhAfgPhiXKS14KHfxFXsAmi2=0auh5J2rmDZn36bDpz85QhGw@mail.gmail.com
обсуждение исходный текст
Ответ на [GENERAL] json aggregation question  (Chris Withers <chris@simplistix.co.uk>)
Список pgsql-general
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Hi Chris,

Maybe there is an another better solution;

1. sending values into jsonb_array_elements to getting elements (lateral join)
2. distinct to eliminate duplicates
3. regexp_replace to remove malformed Array literals
4. Casting into text array

SELECT 
 count(distinct tags ),
string_to_array(regexp_replace(string_agg(distinct elem::text , ','),'\[*\"*\s*\]*','','g'),',') AS list
from thing as t, jsonb_array_elements(t.tags->'tag1') elem
where tags->'tag2'?'t2val1'

count | tag1
2        | {val1,val2,val3}



28 Şub 2017 Sal, 19:22 tarihinde, Chris Withers <chris@simplistix.co.uk> şunu yazdı:
Hi All,

Given the following table:

# create table thing (id serial, tags jsonb);
# \d thing                        Table "public.thing"Column |  Type   |                     Modifiers                      
--------+---------+----------------------------------------------------id     | integer | not null default nextval('thing_id_seq'::regclass)tags   | jsonb   |

...and the following data:

insert into thing (tags) values ('{"tag1": ["val1", "val2"], "tag2": ["t2val1"]}');
insert into thing (tags) values ('{"tag1": ["val3", "val1"], "tag2": ["t2val1"]}');
insert into thing (tags) values ('{"tag1": ["val2", "val1"], "tag2": ["t2val2"]}');

How can I aggregate the results of a query that equates to "show me the number of matching rows and the set of tag1 value that have a tag2 value of t2val1?

The closes I can get is:

# select count(*), json_agg(tags) from thing where tags->'tag2'?'t2val1';count |                                             json_agg                                             
-------+--------------------------------------------------------------------------------------------------    2 | [{"tag1": ["val1", "val2"], "tag2": ["t2val1"]}, {"tag1": ["val3", "val1"], "tag2": ["t2val1"]}]
(1 row)

...but I really want:

 count |     tag1                                             
-------+-------------------------    2 | ["val1", "val2", "val3"]
(1 row)
cheers,

Chris

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