I can take a guess...
> Well, I understand why, but type 'char' is *fixed* length type,
> so even if I don't use some attributes, it *must* be inserted
> with all spaces... At least, I expected this... In this case
> I must get "tuple is too big" even if I will insert "empty"
> record. It is not so - why?
Your first insertion had nulls for the other two positions. Tuples are
stored with a bit vector specifying which columns are null. Null columns
are not stored. So the example fit into one page, no problem. If you had
inserted empty strings in the other two char()s, then you would have run
out of space.
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