Fix potential premature finish in Delta CDF function

[homar]

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# Section
* Fix some things. ({issue}`issuenumber`)

[alexjo2144]

The produced method has a requireNonNull check: https://github.com/trinodb/trino/blob/master/core/trino-spi/src/main/java/io/trino/spi/function/table/TableFunctionProcessorState.java#L89

[homar]

yeah sorry for this

[findepi]

fmt expects line break before else

}
else {

[homar]

i will never get used to this format :|

[electrum]

Commit message title is too long: https://cbea.ms/git-commit/

[electrum]

The commit message should be something like "Fix XXX for Delta Lake".

[findepi]

The idea behind CPS.getNextPage returning nullable is to break procesisng producing a page takes too long.

I think we should yield here. There are 3 ways we can go about it

• returning TableFunctionProcessorState.Blocked.blocked(NOT_BLOCKED)
• returning TableFunctionProcessorState.Processed.produced(EMPTY_PAGE)
• introducing new TableFunctionProcessorState.Yielded

let's go with TableFunctionProcessorState.Processed.produced(EMPTY_PAGE) for a quick fix
and let's follow up with a PR introducing TableFunctionProcessorState.Yielded state

[findepi]

redundant else

[findepi]

redundant else

[findepi]

i tried to understand whether deltaLakePageSource.getNextPage() can actually return a null.
I.e. whether we're dealing with a user-facing correctness bug.

this led me to this question: https://github.com/trinodb/trino/pull/13246/files#r1239083632
cc @raunaqmorarka