Re: So what's an "empty" array anyway?
От | Robert Haas |
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Тема | Re: So what's an "empty" array anyway? |
Дата | |
Msg-id | 603c8f070811120646u466ed30q655843f857e35e8a@mail.gmail.com обсуждение исходный текст |
Ответ на | Re: So what's an "empty" array anyway? (Peter Eisentraut <peter_e@gmx.net>) |
Ответы |
Re: So what's an "empty" array anyway?
Re: So what's an "empty" array anyway? |
Список | pgsql-hackers |
> It was pointed out to me today that a zero-dimensional matrix is a scalar. > This makes a bit of sense, if you say that > > '{{56}}' is of type int[][], 2 dimensions > '{56}' is of type int[], 1 dimension > '56' is of type int, 0 dimensions > > Notice that the number of brace pairs in the literal matches the number of > bracket pairs in the type declaration. > > By that logic, '{}' has one dimension. I think this also works best in > practice, for example with array concatenation. I think it's actually more correct to say that {} has an undefined number of dimensions. The || operator is valid only if the dimensions of the two arrays are equal (in which case it appends them) or if the dimension of one of the arrays is one less than the other (in which case, if legal, it treats the array of lesser dimension as a new element to be added to the other array). But {}, and ONLY {}, can be concatenated with an array of any number of dimensions. ...Robert
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