fix-3091 added simple mapping for constatnt expressions

[bhavnajindal]

Issue: https://github.ibm.com/ClickHouse/issue-repo/issues/3091

Changelog category (leave one):

• Improvement

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):

Requirement was to add a direct mapping without using expression inside the array. Therefore, now computing the index first and then passing it to CH SQL only for constant numerical expressions.

Query:
select * from kql(events | project custom_prop_value[0] | take 1)

Output:

SELECT *
FROM
(
    SELECT custom_prop_value[1] AS Column1
    FROM events
    LIMIT 1
)

[bkuschel]

This is an automated comment for commit ef5abbf with description of existing statuses. It's updated for the latest CI running
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[kashwy]

add some test cases of negative index

[kashwy]

can this recursive case be solved too?

[bhavnajindal]

We would need to get the value of B[2] to correctly map it, which isn't available during Parsing. Therefore, treating B[2] as an arbitrary expression.

[kashwy]

We would need to get the value of B[2] to correctly map it, which isn't available during Parsing. Therefore, treating B[2] as an arbitrary expression.

ok, that's good