Accessing Arrays - placement of index

Documentation feedback

• Page title: Selecting data
• Page URL: https://crate.io/docs/crate/reference/en/latest/general/dql/selects.html
• Source: https://github.com/crate/crate/blob/master/docs/general/dql/selects.rst

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From the documentation it is unclear how to correctly access arrays within objects. The example has the index right after the identifier, but it is not clear if information is an object or array:

select name, information[1]['population'] as population from locations
... where information['population'] is not null
... order by name;

Putting the index first look unintuitive

CREATE TABLE test (a OBJECT);
insert into a values({ id = 1, name = 'foo', tags = ['apple', 'banana', 'pear'], size = 3.1415, valid = true });

SELECT a FROM test limit 100;
-- SELECT OK, 1 row in set (0.005 sec)

SELECT a[1]['tags'] FROM test limit 100;
-- SELECT a[1]['tags'] FROM test limit 100; --> apple

SELECT a['tags'][1] FROM test LIMIT 100;
-- SQLActionException[UnsupportedFeatureException: Nested array access is not supported]

[mfussenegger]

@mechanomi I think this is something where we can also look into changing the behavior or support both versions.

This is indeed rather unintuitive:

cr> SELECT a['tags'] FROM test limit 100;
+-----------------------------+
| a['tags']                   |
+-----------------------------+
| ["apple", "banana", "pear"] |
+-----------------------------+
SELECT 1 row in set (0.007 sec)


cr> SELECT ['apple', 'banana', 'pear'][1] FROM test limit 100;
+---------+
| 'apple' |
+---------+
| apple   |
+---------+
SELECT 1 row in set (0.005 sec)

With an explicit cast it would work:

cr> select a['tags']::text[][1] from test;
+--------------+
| a[1]['tags'] |
+--------------+
| apple        |
+--------------+

[proddata]

@mechanomi

Looks good to me.

Though I think there is a small typing error Lucine instead of Lucene in the Limitations section … can’t find the pr