Changes between Initial Version and Version 1 of PackageQuestion

Timestamp:

Jun 6, 2013, 6:41:48 PM (11 years ago)

Author:

darkblueb

Comment:

new

PackageQuestion

@@ +1 @@
+GEOS 3.4 Requirements and Improvements
+-------------------------------------------------------------------------------
+
+Maximum Version, Minimum Version, Packaging and Linking, Oh My !
+
+  The GEOS library and C interface are designed in such a way that a client can
+  link to a generic C Interface lib (libgeos_c), which then calls a second generic library
+  linked by name (libgeos), then finally the actual current version of libgeos.
+  With this setup, multiple versions of GEOS can easily sit side by side. PostGIS
+  uses this convention to link to GEOS.
+  
+  strk> PostGIS links against the geos_c library, which have had 
+         the _same_ SONAME since the very beginning
+
+  When does it make sense to declare a MINIMUM version ?
+   when entry points are called that are only present in newer versions and above
+
+  When does it make sense to declare a MAXIMUM version ?
+   when behavior changes in an incompatible way in a new version, either API 
+   breakage or perhaps the results of a common operation like noding
+
+Minimum Version      
+  For a long while, features and fixes were just added to the newest GEOS, so
+  any client app would just get the newest available GEOS and all is well.
+
+  However, to take advantage of new functionality, clients have to call 
+  entry points explicitly. So a *minimum* version has to be declared.
+  
+  With PostGIS 2.1, if new GEOS functionality is required, then the 
+  *minimum* version might be 3.4.
+  
+Maximum Version
+  With GEOS 3.4, there is a change in noding algorithm, which could have
+  an effect on output. So a client app's results may be different by upgrading to 
+  GEOS 3.4. This change may be undesirable, so a *maximum* version could be declared,
+  saying in effect, if you want the same reliable output, you must not go above v3.3x.
+
+  
+Packaging  --   IANAP  (I am not a packager ;-)
+
+         / -> GDAL -> PostGIS
+ GEOS-> | -> PostGIS
+         \ -> QGis
+
+  GDAL is unique in that it is designed to be an extensible collection of drivers.
+  Since the tools are command line oriented and open source, I suspect a substantial 
+  number of GDAL installs are built from source.
+  
+  Not so with PostGIS. I suspect that the vast majority of PostGIS installs are by
+  official installers and packages *only*. 
+  
+  PostGIS now requires GDAL (for raster). What collection of GDAL drivers are included
+  by an installer or package of PostGIS that provides GDAL ?  and what GEOS version?  
+  Opinions vary on this situation. User surveys and use case based testing are one 
+  option to understand field experience by users.
+
+
+
+Misc Background
+
+  GDAL
+   GDAL is a suite of tools, including gdal raster tools, and ogr vector tools
+   long ago GEOS was optional to build GDAL, and was used only in ogr vector tools
+   in practice, ogr tools have required GEOS for some time (years)
+   
+   gdal the raster tool now uses GEOS in one place, quoting from #gdal
+
+  EvenR>        alg/gdalcutline.cpp needs GEOS for blend distance support
+   
+  QGis 2.0
+   is coming out very soon. If there was a time to make a change, this is a good time
+   to do that
+
+Linkage
+
+  For example on a work XUbuntu Linux machine, I get the following output:
+
+  $ldd /usr/lib/postgresql/9.2/lib/postgis-2.0.so | grep geos
+        libgeos_c.so.1 => /usr/local/lib/libgeos_c.so.1 (0x00007f73b246c000)
+        libgeos-3.3.9dev.so => /usr/local/lib/libgeos-3.3.9dev.so (0x00007f73b1569000)
+
+  $ldd `which qgis` | grep geos
+    .... error output about gdal .so versioning
+        libgeos_c.so.1 => /usr/local/lib/libgeos_c.so.1 (0x00007fd19145d000)
+        libgeos-3.3.9dev.so => /usr/local/lib/libgeos-3.3.9dev.so (0x00007fd18da38000)
+
+  $ldd `which ogrinfo` | grep geos
+        libgeos_c.so.1 => /usr/local/lib/libgeos_c.so.1 (0x00007fd19145d000)
+        libgeos-3.3.9dev.so => /usr/local/lib/libgeos-3.3.9dev.so (0x00007fd18da38000)
+
+  $ldd `which gdalinfo` | grep geos
+        libgeos_c.so.1 => /usr/local/lib/libgeos_c.so.1 (0x00007f0d60454000)
+        libgeos-3.3.9dev.so => /usr/local/lib/libgeos-3.3.9dev.so (0x00007f0d5ca2f000)
+
+  actual libgeos, has naming like this..
+
+  libgeos.so -> libgeos-3.3.9dev.so
+  
+
+My own geos libs on XUbuntu at the moment:
+
+dbb@xps-8300:~$ ls -l /usr/local/lib/*geos*
+-rwxr-xr-x 1 root root 18178990 Oct  1  2012 /usr/local/lib/libgeos-3.3.6dev.so
+-rwxr-xr-x 1 root root 18199357 Jan 22 12:07 /usr/local/lib/libgeos-3.3.7.so
+-rwxr-xr-x 1 root root 18183679 Mar  8 10:58 /usr/local/lib/libgeos-3.3.9dev.so
+-rw-r--r-- 1 root root 49492572 Mar  8 10:58 /usr/local/lib/libgeos.a
+-rw-r--r-- 1 root root  2194792 Mar  8 10:58 /usr/local/lib/libgeos_c.a
+-rwxr-xr-x 1 root root      979 Mar  8 10:58 /usr/local/lib/libgeos_c.la
+lrwxrwxrwx 1 root root       18 Mar  8 10:58 /usr/local/lib/libgeos_c.so -> libgeos_c.so.1.7.9
+lrwxrwxrwx 1 root root       18 Mar  8 10:58 /usr/local/lib/libgeos_c.so.1 -> libgeos_c.so.1.7.9
+-rwxr-xr-x 1 root root  1030668 Oct  1  2012 /usr/local/lib/libgeos_c.so.1.7.6
+-rwxr-xr-x 1 root root  1030668 Jan 22 12:07 /usr/local/lib/libgeos_c.so.1.7.7
+-rwxr-xr-x 1 root root  1029963 Mar  8 10:58 /usr/local/lib/libgeos_c.so.1.7.9
+-rwxr-xr-x 1 root root      956 Mar  8 10:58 /usr/local/lib/libgeos.la
+lrwxrwxrwx 1 root root       19 Mar  8 10:58 /usr/local/lib/libgeos.so -> libgeos-3.3.9dev.so