Hi,
Sorry to come back with these database access suggestions.
I'd like to commit the changes proposed here after as I need it to
access my postgis database and I'd rather keep my local version of
OpenJUMP synchronized with the CVS, but this code is quite important for
database access, and I'd rather get at least one feed back before
committing.
Thanks a lot
Michaël Michaud
Michaël Michaud a écrit :
> Hi,
>
> This one is for datastore api authors (Martin, Jon ?)
> I have a few suggestions/questions about this api implementation, but
> I'd rather have author's advice before any change :
>
> 1/ PostgisValueConverterFactory
> I think that for geometry column, getConverter should return
> WKB_GEOMETRY_MAPPER instead of WKT_GEOMETRY_MAPPER (geometries seem to
> have been stored in wkb instead of wkt since postgis 1.0)
if (dbTypeName.equalsIgnoreCase("geometry"))
// WKB is now the normal way to store geometry in PostGIS
[mmichaud 2007-05-13]
return WKB_GEOMETRY_MAPPER;
>
> 2/ PostgisResultSetConverter
> In init(), if the resultsetmetadata contains more than one geometry,
> we could keep the first one as AttributeType.GEOMETRY and read others
> as AttributeType.STRING instead of throwing an exception.
// Convert the first geometry into AttributeType.GEOMETRY and the
following ones
// into AttributeType.STRINGs [mmichaud 2007-05-13]
if (mapper[i].getType() == AttributeType.GEOMETRY) {
if (featureSchema.getGeometryIndex() == -1) {
colName = "GEOMETRY";
featureSchema.addAttribute(colName, mapper[i].getType());
}
else {
mapper[i] = ValueConverterFactory.STRING_MAPPER;
featureSchema.addAttribute(colName, AttributeType.STRING);
}
}
else {
featureSchema.addAttribute(colName, mapper[i].getType());
}
>
> 3/ PostgisSQLBuilder
> It seems that adding double quotes around field names make it possible
> to query field name either in lower case or in upper case. I don't
> know if there are drawbacks. I saw somewhere in the code
> (PostgisDSMetadata) that you explicitly lower field names.
private String getColumnListSpecifier(
String[] colName, String geomColName)
{
// Added double quotes around each table name in order to read mixed
case table names
// correctly [mmichaud 2007-05-13]
StringBuffer buf = new StringBuffer();
buf.append("AsBinary(\"" + geomColName + "\") as " + geomColName +
"_wkb");
for (int i = 0; i < colName.length; i++) {
if (! geomColName.equalsIgnoreCase(colName[i])) {
buf.append(",\"");
buf.append(colName[i]).append("\"");
}
}
return buf.toString();
}
>
> The last one is a question :
> In the code, the geometry field is changed to binary with
> AsBinary(geometry) before it is read by WKBReader, even if the
> geometry is stored as wkb.
> I tried to read the field as is to avoid the asBinary() overhead but I
> did not succeed.
> I think this is a format pb (wkb vs ewkb ?), but the WKBReader from
> JTS claims to read ewkb.
> May be it is important to keep asBinary function to be able to read
> geometry without regarding its format, but on the other hand, it
> should be nice to be able to write query as
> select geometry, name from country
> instead of
> select asBinary(geometry), name from country, which is a lot less
> intuitive
>
> Cheers, and thanks again for the great lib
>
> Michael
>
>
>
> Michaël Michaud a écrit :
>
>> Hi everybody,
>>
>> I tried to understand differences between the 4 versions of
>> postgresql/postgis drivers I found at different places.
>> Here are the results of my investigations
>> Comments are welcome.
>>
>> *Different versions I found
>> *1 - a plugin (postgis_1_0_0.jar) from 2005 written by Markus Schaber
>> and bundled with OpenJUMP distribution. As far as I could see, the
>> plugin is bundled but unused in the distribution (nothing happened,
>> even after I have had the jar file to the classpath)
>> 2 - a plugin from uwe dalluege distributed as the "PostGIS PlugIn" on
>> OpenJUMP sourceforge site (2006-11-19). May be based on the previous
>> one.
>> 3 - datastore api from vividsolutions added to the code on december
>> of 2005, but not activated in the original jump version
>> 4 - paolo rizzi's SIS plugin for postgresql/postgis and oracle
>> database access, based on the framework developped in 3
>>
>> *Disimilarities between versions*
>> *1 - postgis plugin* 1.0.0
>> - Don't know how to make this postgis_1_0_0.jar work. If it has no
>> use, it should be removed from the distribution
>> *2 - Uwe's postgis plugin*
>> - the plugin is the only one able to create/update the database.
>> Other ones are read only
>> - it works well with postgresql 8.2 and postgis 1.1+
>> - the plugin load data from the load dataset menu and does not use
>> the nice interface from vividsolution in the layer menu (see 3)
>> - the plugin load data (in-memory) and does not offer a select option
>> or a feature-on-demand option
>> *3 - Vividsolutions's framework*
>> - Vividsolutions's datastore api has a nice design and a nice user
>> interface, but at the moment, it is read-only.
>> - the interface make it possible to cache features (in-memory ?) or
>> not (feature on demand ?)
>> - I could not read a posgis table with Vividsolution's api and
>> OpenJUMP until I made two changes in the code :
>> a) in PostgisValueConverterFactory, if dbTypeName is geometry, I
>> return WKB mapper instead of WKT (since postgis 1.0, default storage
>> format in postgis is binary)
>> b) If there are more than one geometry type in the resultset, the
>> second is read as AttributeType.STRING instead of throwing an
>> exception (in a select * statement, I can get more than one geometry
>> from my database).
>> *4 - SIS PlugIn from Paolo Rizzi
>> *- The plugin is based on Vividsolutions's api
>> - It is a read-only driver for postgis and oracle tables
>> - The plugin includes many dependencies (3 Mo). I don't know why it
>> needs all this stuff because there is not much more features in this
>> plugin than in vivid's api (maybe hidden classes for futur work).
>> - I found postgis_1_1_0 in dependencies but I don't know if it is
>> related to 1- and if it is used
>> - I get geometry, int, double and date values, but I cannot get
>> string values when loading a table or a selection !
>>
>> PS : I know there is also a hard work done by projet-SIGLE team to
>> write a generic data/database driver called GDBMS...
>>
>> Hope that helps,
>>
>> Michaël
>>
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>
>
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