Postgres 12

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CREATE OR REPLACE FUNCTION ST_CreateFishnet(
        nrow integer, ncol integer,
        xsize float8, ysize float8,
        x0 float8 DEFAULT 0, y0 float8 DEFAULT 0,
        OUT "row" integer, OUT col integer,
        OUT geom geometry)
    RETURNS SETOF record AS
$$
SELECT i + 1 AS row, j + 1 AS col, ST_Translate(cell, j * $3 + $5, i * $4 + $6) AS geom
FROM generate_series(0, $1 - 1) AS i,
     generate_series(0, $2 - 1) AS j,
(
SELECT ('POLYGON((0 0, 0 '||$4||', '||$3||' '||$4||', '||$3||' 0,0 0))')::geometry AS cell
) AS foo;
$$ LANGUAGE sql IMMUTABLE STRICT;

CREATE TABLE tb AS
SELECT ROW_NUMBER() OVER () AS poly_name, * 
FROM ST_CreateFishnet(3, 3, 10, 10) AS cells;

CREATE FUNCTION



SELECT 9


SELECT * FROM tb q1
WHERE (
  SELECT count(*) FROM tb q2
  WHERE ST_Touches(q2.geom,q1.geom)) <=3;


poly_name
row
col
geom


1
1
1
010300000001000000050000000000000000000000000000000000000000000000000000000000000000002440000000000000244000000000000024400000000000002440000000000000000000000000000000000000000000000000

3
1
3
0103000000010000000500000000000000000034400000000000000000000000000000344000000000000024400000000000003E4000000000000024400000000000003E40000000000000000000000000000034400000000000000000

7
3
1
010300000001000000050000000000000000000000000000000000344000000000000000000000000000003E4000000000000024400000000000003E400000000000002440000000000000344000000000000000000000000000003440

9
3
3
010300000001000000050000000000000000003440000000000000344000000000000034400000000000003E400000000000003E400000000000003E400000000000003E40000000000000344000000000000034400000000000003440



SELECT 4


WITH j AS (
  SELECT 
    q1.poly_name AS p1,q2.poly_name p2, 
    count(*) OVER (PARTITION BY q1.poly_name ) AS qt
  FROM tb q1, tb q2
  WHERE ST_Touches(q2.geom,q1.geom))
SELECT p1,p2 FROM j
WHERE qt <= 3


p1
p2


1
2

1
4

1
5

3
2

3
5

3
6

7
4

7
5

7
8

9
5

9
6

9
8



SELECT 12

poly_name	row	col	geom
1	1	1	010300000001000000050000000000000000000000000000000000000000000000000000000000000000002440000000000000244000000000000024400000000000002440000000000000000000000000000000000000000000000000
3	1	3	0103000000010000000500000000000000000034400000000000000000000000000000344000000000000024400000000000003E4000000000000024400000000000003E40000000000000000000000000000034400000000000000000
7	3	1	010300000001000000050000000000000000000000000000000000344000000000000000000000000000003E4000000000000024400000000000003E400000000000002440000000000000344000000000000000000000000000003440
9	3	3	010300000001000000050000000000000000003440000000000000344000000000000034400000000000003E400000000000003E400000000000003E400000000000003E40000000000000344000000000000034400000000000003440