1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
|
<?xml version="1.0" encoding="UTF-8"?>
<sect1 id="Exceptional_Functions">
<title>Exceptional Functions</title>
<para>These functions are rarely used functions that should only be used if your data is corrupted in someway. They are used for troubleshooting corruption
and also fixing things that should under normal circumstances, never happen.</para>
<refentry id="PostGIS_AddBBox">
<refnamediv>
<refname>PostGIS_AddBBox</refname>
<refpurpose>Add bounding box to the geometry.</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcprototype>
<funcdef>geometry <function>PostGIS_AddBBox</function></funcdef>
<paramdef><type>geometry </type> <parameter>geomA</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsection>
<title>Description</title>
<para>Add bounding box to the geometry. This would make bounding
box based queries faster, but will increase the size of the
geometry.</para>
<note>
<para>Bounding boxes are automatically added to geometries so in general this is not needed
unless the generated bounding box somehow becomes corrupted or you have an old install that is lacking bounding boxes. Then you need to drop the old and readd.</para>
</note>
<para>&curve_support;</para>
</refsection>
<refsection>
<title>Examples</title>
<programlisting>UPDATE sometable
SET the_geom = PostGIS_AddBBox(the_geom)
WHERE PostGIS_HasBBox(the_geom) = false;</programlisting>
</refsection>
<!-- Optionally add a "See Also" section -->
<refsection>
<title>See Also</title>
<para><xref linkend="PostGIS_DropBBox" />, <xref linkend="PostGIS_HasBBox" /></para>
</refsection>
</refentry>
<refentry id="PostGIS_DropBBox">
<refnamediv>
<refname>PostGIS_DropBBox</refname>
<refpurpose>Drop the bounding box cache from the geometry.</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcprototype>
<funcdef>geometry <function>PostGIS_DropBBox</function></funcdef>
<paramdef><type>geometry </type> <parameter>geomA</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsection>
<title>Description</title>
<para>Drop the bounding box cache from the geometry. This reduces
geometry size, but makes bounding-box based queries slower. It is also used to drop a corrupt bounding box. A tale-tell sign of a corrupt cached bounding box
is when your ST_Intersects and other relation queries leave out geometries that rightfully should return true.</para>
<note>
<para>Bounding boxes are automatically added to geometries and improve speed of queries so in general this is not needed
unless the generated bounding box somehow becomes corrupted or you have an old install that is lacking bounding boxes.
Then you need to drop the old and readd. This kind of corruption has been observed in 8.3-8.3.6 series whereby cached bboxes were not always recalculated when a geometry changed and upgrading to a newer version without a dump reload will not
correct already corrupted boxes. So one can manually correct using below and readd the bbox or do a dump reload.</para>
</note>
<para>&curve_support;</para>
</refsection>
<refsection>
<title>Examples</title>
<programlisting>--This example drops bounding boxes where the cached box is not correct
--The force to ST_AsBinary before applying Box2D forces a recalculation of the box, and Box2D applied to the table geometry always
-- returns the cached bounding box.
UPDATE sometable
SET the_geom = PostGIS_DropBBox(the_geom)
WHERE Not (Box2D(ST_AsBinary(the_geom)) = Box2D(the_geom));
UPDATE sometable
SET the_geom = PostGIS_AddBBox(the_geom)
WHERE Not PostGIS_HasBBOX(the_geom);
</programlisting>
</refsection>
<!-- Optionally add a "See Also" section -->
<refsection>
<title>See Also</title>
<para><xref linkend="PostGIS_AddBBox" />, <xref linkend="PostGIS_HasBBox" />, <xref linkend="Box2D" /></para>
</refsection>
</refentry>
<refentry id="PostGIS_HasBBox">
<refnamediv>
<refname>PostGIS_HasBBox</refname>
<refpurpose>Returns TRUE if the bbox of this geometry is cached, FALSE otherwise.</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcprototype>
<funcdef>boolean <function>PostGIS_HasBBox</function></funcdef>
<paramdef><type>geometry </type> <parameter>geomA</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsection>
<title>Description</title>
<para>Returns TRUE if the bbox of this geometry is cached, FALSE
otherwise. Use <xref linkend="PostGIS_AddBBox" /> and <xref linkend="PostGIS_DropBBox" /> to control caching.</para>
<para>&curve_support;</para>
</refsection>
<refsection>
<title>Examples</title>
<programlisting>SELECT the_geom
FROM sometable WHERE PostGIS_HasBBox(the_geom) = false;</programlisting>
</refsection>
<!-- Optionally add a "See Also" section -->
<refsection>
<title>See Also</title>
<para><xref linkend="PostGIS_AddBBox" />, <xref linkend="PostGIS_DropBBox" /></para>
</refsection>
</refentry>
</sect1>
|
