+1 That's a great proposal, Timo.

I like the proposed simplified syntax. Also, being able to convert from or
to a changelog is a really nice to have.

Gustavo

On 2025/03/21 13:23:37 Timo Walther wrote:
> Hi everyone,
>
> I would like to start a discussion about FLIP-517: Better Handling of
> Dynamic Table Primitives with PTFs [1].
>
> In the past months, I have spent a significant amount of time with SQL
> semantics and the SQL standard around PTFs, when designing and
> implementing FLIP-440 [2]. For those of you that have not taken a look
> into the standard, the concept of Polymorphic Table Functions (PTF)
> enables syntax for implementing custom SQL operators. In my opinion,
> they are kind of a revolution in the SQL language. PTFs can take scalar
> values, tables, models (in Flink), and column lists as arguments. With
> these primitives, we can further evolve shortcomings in the Flink SQL
> language by leveraging syntax and semantics.
>
> I would like introduce a couple of built-in PTFs with the goal to make
> the handling of dynamic tables easier for users. Once users understand
> how a PTF works, they can easily select from a list of functions to
> approach a table for snapshots, changelogs, or searching.
>
> The FLIP proposes:
>
> SNAPSHOT()
> SEARCH_KEY()
> TO_CHANGELOG()
> FROM_CHANGELOG()
>
> I'm aware that this is a delicate topic, and might lead to controversial
> discussions. I hope with concise naming and syntax the benefit over the
> existing syntax becomes clear.
>
> There are more useful PTFs to come, but those are the ones that I
> currently see as the most fundamental ones to tell a round story around
> Flink SQL.
>
> Looking forward to your feedback.
>
> Thanks,
> Timo
>
> [1]
>
https://cwiki.apache.org/confluence/display/FLINK/FLIP-517%3A+Better+Handling+of+Dynamic+Table+Primitives+with+PTFs
> [2]
> https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=298781093
>

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