feat(expr): support VARIADIC function arguments

[wangrunji0408]

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What's changed and what's your intention?

resolve #14705

This PR adds VARIADIC argument support for the following functions:

select format('%s %s', variadic array['Hello', 'World']); -> "Hello World"
select concat(variadic array['abcde', '2', NULL, '22']); -> "abcde222"
select concat_ws(',', variadic array['abcde', 2, NULL, 22] :: varchar[]); -> "abcde,2,22"
select jsonb_build_array(variadic array[1, 2, 4, 5]); -> [1, 2, 4, 5]
select jsonb_build_object(variadic array['foo', '1', '2', 'bar']); -> {"2": "bar", "foo": 1}
select jsonb_extract_path('{"a": {"b": ["foo","bar"]}}', variadic array['a', 'b', '1']); -> bar
select jsonb_extract_path_text('{"a": {"b": ["foo","bar"]}}', variadic array['a', 'b', '1']); -> bar

It adds new functions format_variadic, concat_ws_variadic... on the backend, which take a fixed anyarray as the last argument. On the frontend, we rewrite the variadic calls into new functions.

Checklist

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
• I have added test labels as necessary. See details.
• I have added fuzzing tests or opened an issue to track them. (Optional, recommended for new SQL features Sqlsmith: Sql feature generation #7934).
• My PR contains breaking changes. (If it deprecates some features, please create a tracking issue to remove them in the future).
• All checks passed in ./risedev check (or alias, ./risedev c)
• My PR changes performance-critical code. (Please run macro/micro-benchmarks and show the results.)

• My PR contains critical fixes that are necessary to be merged into the latest release. (Please check out the details)

Documentation

• My PR needs documentation updates. (Please use the Release note section below to summarize the impact on users)

Release note

support VARIADIC arguments for the following functions:

• format
• concat_ws
• jsonb_build_array
• jsonb_build_object
• jsonb_extract_path
• jsonb_extract_path_text

The VARIADIC keyword expands the array parameter into one or more occurrences of its element type. See postgres documentation for more details.

Add a new function concat:

concat ( val1 "any" [, val2 "any" [, ...] ] ) → text
Concatenates the text representations of all the arguments. NULL arguments are ignored.
concat('abcde', 2, NULL, 22) → abcde222

[xxchan]

Could you explain the safety of this change?

[xxchan]

So old impl is already variadic?

[wangrunji0408]

Yes. Previously we implemented variadic form in backend, but only accepted non-variadic form in frontend.

[xxchan]

I'm still a little confused about why we need 2 exprs. Isn't variadic version converted to the variadic version? 🤔

Could you add some planner tests to help understand?

[xxchan]

Is this a little confusing 🤔

[wangrunji0408]

This is to allow arguments of list type to be accepted as impl Row in Rust functions.

[BugenZhao]

I'm okay with this as I cannot come up with another way to interpret ARRAY as rows to form an ambiguousness. If there's one, making a newtype on ListRef then impl Row on that will work.

[xxchan]

So old impl is already variadic?

[BugenZhao]

I'm wondering what the possible receiver types are here for impl Row. 👀

[wangrunji0408]

It is RowRef for non-variadic version, and ListRef for variadic version.

[wangrunji0408]

I'm still a little confused about why we need 2 exprs.

• Without VARIADIC keyword, arguments are stored in multiple columns.
• With VARIADIC keyword, arguments are stored as a list in a column.

They are physically different. Converting either form to the other will introduce overhead. So for performance reason, I decided to generate separate code for each version in backend.

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[BugenZhao]

LGTM