[postgis-tickets] [SCM] PostGIS branch master updated. 3.1.0rc1-3-g49e96ec

[git at osgeo.org]

This is an automated email from the git hooks/post-receive script. It was
generated because a ref change was pushed to the repository containing
the project "PostGIS".

The branch, master has been updated
       via  49e96ec4dc650375f80fc2167c0dc375fe6e9c51 (commit)
      from  dcb0192b156b33e4fa5d3b762f73d36ee7b91ee6 (commit)

Those revisions listed above that are new to this repository have
not appeared on any other notification email; so we list those
revisions in full, below.

- Log -----------------------------------------------------------------
commit 49e96ec4dc650375f80fc2167c0dc375fe6e9c51
Author: Martin Davis <mtnclimb at gmail.com>
Date:   Mon Dec 14 18:29:55 2020 -0800

    Improve doc Using Indexes text

diff --git a/doc/using_postgis_query.xml b/doc/using_postgis_query.xml
index cd629b8..b140e13 100644
--- a/doc/using_postgis_query.xml
+++ b/doc/using_postgis_query.xml
@@ -466,8 +466,8 @@ WHERE a.geom && b.geom
     and the distance operators used in nearest-neighbour queries
     (the most common being <xref linkend="geometry_distance_knn" />.)
     Index-aware functions include most of the named spatial predicates
-    (such as <xref linkend="ST_Intersects" />), and most of the distance predicates such as
-    <xref linkend="ST_DWithin" />.)
+    (such as <xref linkend="ST_Intersects" />), and most of the distance predicates
+    (such as <xref linkend="ST_DWithin" />.)
     </para>
     <para>
      Functions such as
@@ -486,7 +486,7 @@ WHERE ST_Distance(the_geom, 'SRID=312;POINT(100000 200000)') < 100</programli
     is computed for <emphasis role="bold">every</emphasis> row in the table.
     </para>
     <para>
-    We can reduce the number of distance calculations required by using the
+    We can reduce the number of rows processed by using the
 	index-aware function <xref linkend="ST_DWithin" />:</para>
 
 	  <programlisting>SELECT the_geom
@@ -495,15 +495,17 @@ WHERE ST_DWithin(the_geom, 'SRID=312;POINT(100000 200000)', 100)
 </programlisting>
 
     <para>This query selects the same geometries, but it does it in a more
-    efficient way. If there is a GiST index on the_geom, the query
-    planner will recognize that it can use the index to reduce the number of
-    rows before calculating the distance.
+    efficient way.
     This is enabled by <varname>ST_DWithin()</varname> using the
     <varname>&&</varname> operator internally on an expanded bounding box
     of the query geometry.
-    That uses the spatial index to find only records with geometries
+    If there is a spatial index on <code>the_geom</code>, the query
+    planner will recognize that it can use the index to reduce the number of
+    rows scanned before calculating the distance.
+    The spatial index allows retrieving only records with geometries
     whose bounding boxes overlap the expanded extent
-    (or in other words, skips records with geometries which are guaranteed to be too far away.)
+    and hence which <emphasis>might</emphasis> be within the required distance.
+    The actual distance is then computed to confirm whether to include the record in the result set.
     </para>
 
 	</sect2>

-----------------------------------------------------------------------

Summary of changes:
 doc/using_postgis_query.xml | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)


hooks/post-receive
-- 
PostGIS