[CALCITE-7732] Make the TABLE keyword optional for table function calls in LATERAL context

[darpan-14]

Jira Link

CALCITE-7732

Changes Proposed

Calcite allows table functions in the FROM clause without the TABLE(...)
wrapper:

SELECT *
FROM fn(args)

However, explicitly specifying LATERAL currently makes the wrapper mandatory:

SELECT *
FROM t, LATERAL TABLE(fn(t.a))

This change makes TABLE optional in that context, allowing:

SELECT *
FROM t, LATERAL fn(t.a)

The existing wrapped syntax remains supported and unchanged.

The parser recognizes unqualified and schema-qualified function names and
constructs the same LATERAL and COLLECTION_TABLE parse tree used by the
wrapped form. Existing handling of LATERAL TABLE(...), LATERAL UNNEST(...),
and lateral subqueries remains unchanged.

[mihaibudiu]

I am not crazy about this function. Is there a simpler way to do it, maybe by refactoring the grammar a bit?

[darpan-14]

Thanks for the review, have updated the implementation. Could you please check again?

[mihaibudiu]

This is much better; please squash the commits for merging
Also, please note that your commit message is not the same as the JIRA issue

[darpan-14]

Thanks @mihaibudiu , have updated commit message as well as PR title according to convention.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

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