From: | Tatsuo Ishii <ishii(at)postgresql(dot)org> |
---|---|
To: | stark(at)enterprisedb(dot)com |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Cool hack with recursive queries |
Date: | 2008-11-20 03:53:52 |
Message-ID: | 20081120.125352.124570784.t-ishii@sraoss.co.jp |
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Thread: | |
Lists: | pgsql-hackers |
> So based on Graeme Job's T-SQL hack over at thedailywtf.com I adapted the
> T-SQL code to Postgres and got this. Thought others might find it amusing.
>
> WITH RECURSIVE Z(IX, IY, CX, CY, X, Y, I) AS (
> SELECT IX, IY, X::float, Y::float, X::float, Y::float, 0
> FROM (select -2.2 + 0.031 * i, i from generate_series(0,101) as i) as xgen(x,ix),
> (select -1.5 + 0.031 * i, i from generate_series(0,101) as i) as ygen(y,iy)
> UNION ALL
> SELECT IX, IY, CX, CY, X * X - Y * Y + CX AS X, Y * X * 2 + CY, I + 1
> FROM Z
> WHERE X * X + Y * Y < 16::float
> AND I < 100
> )
> SELECT array_to_string(array_agg(SUBSTRING(' .,,,-----++++%%%%@@@@#### ', LEAST(GREATEST(I,1),27), 1)),'')
> FROM (
> SELECT IX, IY, MAX(I) AS I
> FROM Z
> GROUP BY IY, IX
> ORDER BY IY, IX
> ) AS ZT
> GROUP BY IY
> ORDER BY IY
Is it a Mandelbrot? How nice!
--
Tatsuo Ishii
SRA OSS, Inc. Japan
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