What is the meaning of && in PostGIS?

Question

In PostGIS, what is the result of the && operation between two geometries? In my mind, && returns a boolean, but does return geometry this time. In the following example, the operation is between a LineString and a Polygon.

Firstly, I guess this is the relationship between inclusion and being included. Until I do the following example, I think this should be a relationship of type "intersection". Am I right?

select ST_geomfromtext('linestring(0.1 0.1,1.9 1.9)', 4326) && st_geomfromtext('POLYGON((0 0,0 1,1 1,1 0,0 0))', 4326)

The result is t which represents true.

Note that `&&` is also the "overlaps" operator for [arrays](https://www.postgresql.org/docs/current/functions-array.html) and [ranges](https://www.postgresql.org/docs/current/functions-range.html) and the `AND` operator for [full text search](https://www.postgresql.org/docs/current/functions-textsearch.html) — , Aug 02 '19 at 05:09

score 14 · Accepted Answer · edited Jun 20 '20 at 09:12

14

It's an intersection operator &&

boolean &&( geometry A , geometry B );

boolean &&( geography A , geography B );

The && operator returns TRUE if the 2D bounding box of geometry A intersects the 2D bounding box of geometry B.

How one could find it using google:

Search for "postgis operators"
On the first page https://postgis.net/docs/reference.html search for &&

edited Jun 20 '20 at 09:12

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answered Aug 02 '19 at 02:35

zerkms

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Think you very much ,It's just what I need. – sh g Aug 02 '19 at 02:38
They should have had human-readable operator there, like INTERSECTS_WITH, rather then going with &&. – jayarjo Apr 10 '20 at 07:43
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@jayarjo it's a domain specific knowledge: from set theory it's known that sets intersection (or conjunction) is a `∧` or `&`. – zerkms Apr 10 '20 at 09:11
Thanks for the info. And still - it's SQL we are dealing with, they should have followed usual conventions. – jayarjo Apr 10 '20 at 09:51
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@jayarjo `ST_Intersects` ? – zerkms Apr 10 '20 at 09:58
Is it an equivalent? Awesome. – jayarjo Apr 10 '20 at 10:04
ST_Intersects is a PostGIS Function - I'm not sure if it can perform intersects on non-geometric / geographic types or arrays, whereas I was able to use && to assess the overlap of date ranges, for example – user2274903 Jul 31 '20 at 06:22

score 0 · Answer 2 · answered Apr 18 '22 at 10:57

diff between && and st_intersect.
https://postgis.net/docs/ST_Intersects.html

If a geometry or geography shares any portion of space then they intersect. For geography -- tolerance is 0.00001 meters (so any points that are close are considered to intersect)

So it's possible that boolean &&( geometry A , geometry B ); return true, but st_intersects(geometry A, geometry B) return false. example: https://postgis.net/workshops/postgis-intro/indexing.html

But boolean st_intersects(geometry A, geometry B) will yield the same result as boolean &&( geometry A , geometry B );

What is the meaning of && in PostGIS?

2 Answers2