Docs: Define "tuple"

[sploiselle]

Many references to tuples in the functions and operators doc, but tuples themselves don't have their own doc and don't appear to be defined anywhere.

Once I looked up what they were, I realized I knew them by sight but not by name, but having a reference doc doesn't hurt.

• PostgreSQL only has a few mailer questions post (1, 2).
• MSDN has incomprehensible developer gunk, which might or might not be proprietary to SQL Server 2016.
• MySQL doesn't have anything official showing up on Google pg 1.

However, simple explanations exist and CockroachDB could offer something great to its users.

[knz]

I would gladly volunteer to look at this during a docs fixit day.

[knz]

Note: the "simple explanation" given as first answer on http://stackoverflow.com/questions/751264/what-does-the-term-tuple-mean-in-relational-databases is actually plainly wrong and inapplicable to cockroachdb.

[sploiselle]

No one else has been confused by this, seemingly. Going to close this issue.