%ex1.5

\begin{enumerate}[label=(\alph*)]
% (a)
	\item
Optimized query:
\begin{verbatim}
SELECT distinct(displayname) FROM posts p JOIN users u ON u.id = p.owneruserid WHERE p.viewcount > u.views;
\end{verbatim}

Original version:
\begin{verbatim}
 Planning time: 0.978 ms
 Execution time: 86179.847 ms
\end{verbatim}

Optimized version:
\begin{verbatim}
 Planning time: 0.960 ms
 Execution time: 37.354 ms
\end{verbatim}

% (b)
	\item
Optimized query:
\begin{verbatim}
SELECT score FROM comments WHERE text ILIKE 'yes\%'; <- did not work (100ms instead of 33ms)
\end{verbatim}

Original version:
\begin{verbatim}
 Planning time: 0.540 ms
 Execution time: 60.946 ms
\end{verbatim}

Optimized version:
\begin{verbatim}
TODO, current query is slower..
\end{verbatim}

% (b)
	\item
Optimized query:
\begin{verbatim}
SELECT DISTINCT postid FROM votes WHERE postid NOT IN (SELECT postid FROM votes WHERE votetypeid != 2);
\end{verbatim}

Improvements:\\
Instead of doing about twelve million Seq Scans this is now reduces it to two Seq Scans by inverting the condition.

Original version:
\begin{verbatim}
Did not terminate. On a different machine with SSD and no time limit it took 16 minutes.
\end{verbatim}

Optimized version:
\begin{verbatim}
 Planning time: 1.093 ms
 Execution time: 81.776 ms
\end{verbatim}

% (d)
	\item
Optimized query:
\begin{verbatim}
SELECT p.*, c.*, u.* FROM posts p JOIN comments c ON p.id = c.postid JOIN users u ON p.owneruserid = u.id JOIN badges b on u.id = b.userid WHERE u.upvotes+3 >= (SELECT AVG(upvotes) FROM users WHERE u.creationdate > c.creationdate) AND EXISTS (SELECT 1 FROM postlinks l WHERE l.relatedpostid > p.id) AND b.name IN ('Autobiographer','Supporter');
\end{verbatim}

Original version:
\begin{verbatim}
 Planning time: 4.084 ms
 Execution time: 4006.044 ms
\end{verbatim}

Optimized version:
\begin{verbatim}
 Planning time: 2.954 ms
 Execution time: 3081.461 ms
\end{verbatim}
\end{enumerate}
