YugabyteDB not using expression index on json column - yugabytedb

Question

[Question posted by a user of YugabyteDB]
I'm having difficulty making the query planner use the index in the query below:
postgres=# create table books(k int primary key, doc jsonb not null);
postgres=# CREATE INDEX books_year
ON books (((doc->>'year')::int) ASC)
WHERE doc->>'year' is not null;
postgres=# EXPLAIN select
(doc->>'ISBN')::bigint as isbn,
doc->>'title' as title,
(doc->>'year')::int as year
from books
where (doc->>'year')::int > 1850
order by 3;
QUERY PLAN
-----------------------------------------------------------------
Sort (cost=177.33..179.83 rows=1000 width=44)
Sort Key: (((doc ->> 'year'::text))::integer)
-> Seq Scan on books (cost=0.00..127.50 rows=1000 width=44)
Filter: (((doc ->> 'year'::text))::integer > 1850)
(4 rows)
While querying by string value, looks like it's using it:
postgres=# EXPLAIN select
(doc->>'ISBN')::bigint as isbn,
doc->>'title' as title,
(doc->>'year')::int as year
from books
where (doc->>'year') = '1988'
order by 3;
QUERY PLAN
------------------------------------------------------------------------------
Index Scan using books_year on books (cost=0.00..125.50 rows=1000 width=44)
Filter: ((doc ->> 'year'::text) = '1988'::text)
(2 rows)

Answer 1

The predicate on the index and query must match like below:
postgres=# CREATE INDEX books_year ON books (((doc->>'year')::int) asc) where doc->>'year' is not null;
postgres=# EXPLAIN select
(doc->>'ISBN')::bigint as isbn,
doc->>'title' as title,
(doc->>'year')::int as year
from books
where (doc->>'year')::int > 1850 and doc->>'year' is not null;
QUERY PLAN
--------------------------------------------------------------------------
Index Scan using books_year on books (cost=0.00..5.24 rows=10 width=44)
Index Cond: (((doc ->> 'year'::text))::integer > 1850)
(2 rows)