\begin{frame}
  \frametitle{Intention Locks}
  
  \begin{goal}{Multi-granularity Locking Protocol}
    \begin{itemize}
      \item Before a granule $g$ can be locked in S (or X) mode,\\
        the transaction has to obtain an IS (or IX) lock\\
        on \emph{all coarser} granularities that contain $g$. 
      \item After all intention locks are granted, the transaction can lock g in the announced mode.
    \end{itemize}
  \end{goal}
  \pause
  
  \begin{exampleblock}{}
    The query $Q_1$ would for example:
      \begin{itemize}
        \item obtain an \emph{IS lock} on the \emph{database}
        \item obtain an \emph{IS lock} on the \emph{table} \sql{Customers}
      \end{itemize}
    Afterwards obtain an \emph{S lock} on the \emph{row} with \sql{id = 42}.
  \end{exampleblock}
  \pause

  \begin{exampleblock}{}
    The query $Q_2$ would for example:
      \begin{itemize}
        \item obtain an \emph{IS lock} on the \emph{database}
      \end{itemize}
    Afterwards obtain an \emph{S lock} on the \emph{table} \sql{Customers}.
  \end{exampleblock}
\end{frame}