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https://issues.apache.org/jira/browse/CALCITE-7732?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Darpan Lunagariya (e6data) reassigned CALCITE-7732:
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Assignee: Darpan Lunagariya (e6data)
> Make the TABLE keyword optional for table function calls in LATERAL context
> ---------------------------------------------------------------------------
>
> Key: CALCITE-7732
> URL: https://issues.apache.org/jira/browse/CALCITE-7732
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Reporter: Fabian Hueske
> Assignee: Darpan Lunagariya (e6data)
> Priority: Major
>
> h3. Summary
> Calcite currently requires the {{TABLE}} keyword when a table function is
> invoked together with the explicit {{LATERAL}} keyword. This issue proposes
> making {{TABLE}} optional in that position, so that both of the following are
> accepted:
> {code:sql}
> -- explicit form (still supported, unchanged)
> SELECT * FROM t, LATERAL TABLE(fn(t.a))
> -- new, TABLE keyword omitted
> SELECT * FROM t, LATERAL fn(t.a)
> {code}
> The {{TABLE}} keyword remains fully supported, it simply becomes optional.
> Existing queries continue to parse and behave exactly as before; this is a
> purely additive, backward-compatible change.
> h3. Motivation
> As of CALCITE-6254 (1.37.0), a table function can be invoked in the
> {{{}FROM{}}}/{{{}JOIN{}}} position without the {{TABLE(...)}} wrapper:
> {code:sql}
> SELECT * FROM fn(args) -- OK since 1.37.0
> SELECT * FROM t JOIN fn(args) ON ...
> {code}
> However, once the {{LATERAL}} keyword is written explicitly, the {{TABLE}}
> wrapper becomes mandatory again. This leaves an inconsistent matrix:
> ||Syntax||Supported today||
> |{{FROM t, fn(args)}} (implicit lateral, no {{{}TABLE{}}})|(/) (CALCITE-6254)|
> |{{FROM t, LATERAL TABLE(fn(args))}}|(/)|
> |{{FROM t, TABLE(fn(args))}}|(/)|
> |{{FROM t, LATERAL fn(args)}}|(x)|
> Requiring {{TABLE}} _only_ when {{LATERAL}} is spelled out is a syntactic
> inconsistency. The {{TABLE}} keyword adds no information in this context and
> bloats the syntax. Several vendors treat it as optional. Making it optional
> under {{LATERAL}} completes the matrix and aligns the two spellings.
> h3. Backward compatibility
> Fully backward compatible:
> * {{TABLE}} stays a legal, supported keyword — it is only made optional.
> * All existing queries ({{{}LATERAL TABLE(fn(...)){}}},
> {{{}TABLE(fn(...)){}}}, plain {{{}fn(...){}}}) parse and behave identically.
> * The change only adds an optional syntax path; no existing behavior is
> removed or altered.
> h3. References
> * CALCITE-6254 — Support table function calls in FROM clause without TABLE()
> wrapper (direct precedent, 1.37.0)
> * CALCITE-1490 — Allow table functions without explicit TABLE (dup of 6254)
> * CALCITE-4396 — Allow table valued functions in FROM and JOIN without TABLE
> clause (dup of 6254)
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