What Is a Slot?


A narrow opening or groove, such as the kind into which a letter or postcard can be slipped. Also, in aviation, any of several openings in the wing or tail surface of an airplane used to control air flow, such as an aileron or flap. (colloquial, US) To place in a slot; to allocate or assign to a slot.

A machine that accepts cash or, in the case of “ticket-in, ticket-out” machines, paper tickets with a barcode, to give out credits based on combinations of symbols. Most slots have a theme and a variety of features aligned with it, including symbols, jackpots, bonus rounds, and other special effects.

Unlike blackjack, where your skill can impact the outcome of a hand, winning a jackpot at a slot machine requires split-second timing and luck. The random-number generator at the heart of every slot machine produces dozens of numbers per second, and each possible combination on the reels is assigned a different number. When the machine receives a signal (from a button being pushed or, on older machines, a handle being pulled), the computer uses an internal sequence table to map the number to a specific stop on the reels.

In BigQuery, a slot is a dynamic placeholder that either waits for content to be added to it (a passive slot) or calls out to a renderer to fill it. When a query’s capacity demands change due to a schedule or another factor, BigQuery automatically re-evaluates the available slots and reassigns them as necessary.