Postgres Can Do That

https://medium.com/cognite/postgres-can-do-that-f221a8046e

• Author: alex brasetvik
• Link: https://medium.com/cognite/postgres-can-do-that-f221a8046e
• Publish Date: 2021.12.06
• Reviewed Date: 2022-01-26

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• Query Tuning with Explain
• Writeable Cte

Generate a mandelbrot set

--Mandelbrot set
WITH RECURSIVE x(i) AS (
	VALUES(0)
	UNION ALL
	SELECT i + 1 FROM x WHERE i < 101
),
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 x) AS xgen(x, ix)
		CROSS JOIN (SELECT -1.5 + 0.031 * i, i FROM x) 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 < 16.0 AND I < 27
),
Zt (Ix, Iy, I) AS (
	SELECT Ix, Iy, MAX (I) AS I
	FROM Z
	GROUP BY Iy, Ix
	ORDER BY Iy, Ix
)
SELECT array_to_string(
	array_agg(
		SUBSTRING(
			' .,,,-----++++%%%%@@@@#### ',
			GREATEST (I,1),
			1
		)
	),''
)
FROM Zt
GROUP BY Iy
ORDER BY Iy;

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Backlinks

• 2022-01-26 (DevLog)