Add Optional Variadic Invocation Explanation to 35.4.5 (xfunc-sql)

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От David Johnston
Тема Add Optional Variadic Invocation Explanation to 35.4.5 (xfunc-sql)
Дата
Msg-id CAKFQuwaomm_7N9Y_9pd43eXgMyQxzogtjD4CJxjaxk05QsF1pw@mail.gmail.com
обсуждение исходный текст
Ответы Re: Add Optional Variadic Invocation Explanation to 35.4.5 (xfunc-sql)  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-docs
CREATE FUNCTION varfunc (fixed1 text, VARIADIC vars text[]) [...]

SELECT varfunc('text fixed 1'); -- error: function signature not found; thus the number of supplied variadic values must be >= 1

Describes how to invoke a function defined with VARIADIC with an actual array as input instead of supplying ONE-or-more individual arguments to the call.

AFAICS the only way to get the called function to see an empty array is to call it like:

SELECT varchar('text fixed 1', VARIADIC ARRAY[]::text[])

While this is a logical solution to the problem, given the above knowledge, it would be nice if both points were made explicitly in the documentation in the section linked above.

Existing: "Sometimes it is useful to be able to pass an already-constructed array to a variadic function; this is particularly handy when one variadic function wants to pass on its array parameter to another one."

Change that to:

"Sometimes it is useful to be able to pass an already-constructed array to a variadic function."
<move existing sample to here>
"While this is particularly handy when one variadic function wants to pass on its array parameter to another[/cut] it is required if you wish to invoke the function without passing any optional arguments.  The following example's first attempt to omit the variadic argument fails since the planner looks for a different function signature.  By using the variadic invocation the second attempt succeeds. The alternative is to define an overloaded function without a VARIADIC parameter but with the same non-optional ones."
<better example maybe...but show/explain the two queries above>

Thoughts?  Am I missing something?

David J.

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