<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
---
- [[query-tuning-with-explain]]
- [[( 2022-01-26 Postgres Can Do That]]
Generate a mandelbrot set
```sql
--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;
```