Querying Postgres Table with JSONB data - sql

Question

I have a Table which stores data in a JSONB column.
Now, what i want to do is, query that table, and fetch records, which have specific values for a key.
This works fine:
SELECT "documents".*
FROM "documents"
WHERE (data #> '{"type": "foo"}')
But what i want to do is, fetch all the rows in the table, which have types foo OR bar.
I tried this:
SELECT "documents".*
FROM "documents"
WHERE (data #> '{"type": ["foo", "bar"]}')
But this doesn't seem to work.
I also tried this:
SELECT "documents".*
FROM "documents"
WHERE (data->'type' ?| array['foo', 'bar'])
Which works, but if I specify a key like so data->'type' it takes away the dynamicity of the query.
BTW, I am using Ruby on Rails with Postgres, so all the queries are going through ActiveRecord. This is how:
Document.where("data #> ?", query)

Answer 1

if I specify a key like so data->'type' it takes away the dynamicity of the query.
I understand you have a gin index on the column data defined like this:
CREATE INDEX ON documents USING GIN (data);
The index works for this query:
EXPLAIN ANALYSE
SELECT "documents".*
FROM "documents"
WHERE data #> '{"type": "foo"}';
QUERY PLAN
------------------------------------------------------------------------------------------------------------------------------
Bitmap Heap Scan on documents (cost=30.32..857.00 rows=300 width=25) (actual time=0.639..0.640 rows=1 loops=1)
Recheck Cond: (data #> '{"type": "foo"}'::jsonb)
Heap Blocks: exact=1
-> Bitmap Index Scan on documents_data_idx (cost=0.00..30.25 rows=300 width=0) (actual time=0.581..0.581 rows=1 loops=1)
Index Cond: (data #> '{"type": "foo"}'::jsonb)
Planning time: 7.928 ms
Execution time: 0.841 ms
but not for this one:
EXPLAIN ANALYSE
SELECT "documents".*
FROM "documents"
WHERE (data->'type' ?| array['foo', 'bar']);
QUERY PLAN
-----------------------------------------------------------------------------------------------------------
Seq Scan on documents (cost=0.00..6702.98 rows=300 width=25) (actual time=31.895..92.813 rows=2 loops=1)
Filter: ((data -> 'type'::text) ?| '{foo,bar}'::text[])
Rows Removed by Filter: 299997
Planning time: 1.836 ms
Execution time: 92.839 ms
Solution 1. Use the operator #> twice, the index will be used for both conditions:
EXPLAIN ANALYSE
SELECT "documents".*
FROM "documents"
WHERE data #> '{"type": "foo"}'
OR data #> '{"type": "bar"}';
QUERY PLAN
------------------------------------------------------------------------------------------------------------------------------------
Bitmap Heap Scan on documents (cost=60.80..1408.13 rows=600 width=25) (actual time=0.222..0.233 rows=2 loops=1)
Recheck Cond: ((data #> '{"type": "foo"}'::jsonb) OR (data #> '{"type": "bar"}'::jsonb))
Heap Blocks: exact=2
-> BitmapOr (cost=60.80..60.80 rows=600 width=0) (actual time=0.204..0.204 rows=0 loops=1)
-> Bitmap Index Scan on documents_data_idx (cost=0.00..30.25 rows=300 width=0) (actual time=0.144..0.144 rows=1 loops=1)
Index Cond: (data #> '{"type": "foo"}'::jsonb)
-> Bitmap Index Scan on documents_data_idx (cost=0.00..30.25 rows=300 width=0) (actual time=0.059..0.059 rows=1 loops=1)
Index Cond: (data #> '{"type": "bar"}'::jsonb)
Planning time: 3.170 ms
Execution time: 0.289 ms
Solution 2. Create an additional index on (data->'type'):
CREATE INDEX ON documents USING GIN ((data->'type'));
EXPLAIN ANALYSE
SELECT "documents".*
FROM "documents"
WHERE (data->'type' ?| array['foo', 'bar']);
QUERY PLAN
------------------------------------------------------------------------------------------------------------------------------
Bitmap Heap Scan on documents (cost=30.32..857.75 rows=300 width=25) (actual time=0.056..0.067 rows=2 loops=1)
Recheck Cond: ((data -> 'type'::text) ?| '{foo,bar}'::text[])
Heap Blocks: exact=2
-> Bitmap Index Scan on documents_expr_idx (cost=0.00..30.25 rows=300 width=0) (actual time=0.035..0.035 rows=2 loops=1)
Index Cond: ((data -> 'type'::text) ?| '{foo,bar}'::text[])
Planning time: 2.951 ms
Execution time: 0.108 ms
Solution 3. In fact this is a variant of the solution 1, with a different format of the condition which may be more convenient to use by the client program:
EXPLAIN ANALYSE
SELECT "documents".*
FROM "documents"
WHERE data #> any(array['{"type": "foo"}', '{"type": "bar"}']::jsonb[]);
QUERY PLAN
------------------------------------------------------------------------------------------------------------------------------
Bitmap Heap Scan on documents (cost=60.65..1544.20 rows=600 width=26) (actual time=0.803..0.819 rows=2 loops=1)
Recheck Cond: (data #> ANY ('{"{\"type\": \"foo\"}","{\"type\": \"bar\"}"}'::jsonb[]))
Heap Blocks: exact=2
-> Bitmap Index Scan on documents_data_idx (cost=0.00..60.50 rows=600 width=0) (actual time=0.778..0.778 rows=2 loops=1)
Index Cond: (data #> ANY ('{"{\"type\": \"foo\"}","{\"type\": \"bar\"}"}'::jsonb[]))
Planning time: 2.080 ms
Execution time: 0.304 ms
(7 rows)
Read more in the documentation.