Composite JSONB array query in Postgres?

问题

Table: test, JSONB column: content:

create table test (id bigserial primary key, content jsonb);

content contains a list of fixed-length lists:

insert into test values (1, '[["first 1", "second 3"]]');
insert into test values (2, '[["first 1", "second 2"], ["first 2", "second 3"]]');
insert into test values (3, '[["first 1", "second 2"], ["first 1", "second 3"]]');
insert into test values (4, '[["first 2", "second 3"], ["first 1", "second 2"], ["first 1", "second 2"]]');

What's the correct Postgres syntax for a query that returns all rows where at least one of the content elements satisfies (first element = "first 1") AND (second element ILIKE "%3%")?

That is, in the example above, it should select rows 1 and 3, but not 2 or 4.

Bonus question: what is the most efficient way to do such query (in case there are multiple alternatives)? Does it make sense to look into GIN over JSONB with pg_trgm? (There are millions of rows, the inner string values are typically 10-100 characters long, and each content list contains 0-1000s of lists (most usually 0).)

Thanks!

回答1:

Inner select expands array elements into separate rows with jsonb_array_elements, outer select does the filtering you want. See SQL Fiddle for live example.

select * from (
select id, jsonb_array_elements(content) as item from test  
) as expandedtest
where item->>0 like 'first 1' and item->>1 like '%3%'

回答2:

You should split apart the top level arrays and check the elements from there:

select distinct id, content
FROM test
JOIN lateral (
    select elems 
    FROM jsonb_array_elements(content) jae(elems)
) all_arrays ON TRUE
WHERE elems ->> 0 = 'first 1'
and elems ->> 1 ilike '%3%'
ORDER BY 1;

As for the best way to do this, that depends a lot on your actual data - how many rows, how big these jsonb structures are, etc. In general, though, a search like ilike '%3%' will benefit from indexes based off of pg_trgm because they can't use traditional btree indexes.

Edit: @Abelisto's query in the comments is better because it should be more performant, especially if content can contain 1000s of elements:

select * from test 
where exists 
  (select 1 
   from jsonb_array_elements(content) jae(elems) 
   where elems ->> 0 = 'first 1' 
   and elems ->> 1 ilike '%3%'
  );

来源：https://stackoverflow.com/questions/56483600/composite-jsonb-array-query-in-postgres

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postgresql

jsonb