[postgis-users] Length of Bigint, Double and Text fields

[Aigars V]

http://mixed.dans.knaw.nl/files/TI838D.txt



2009/12/1 Gerald Creager <gerry.creager at tamu.edu>

> My experience in the past (including some .dbf imports by several systems,
> including legaccy dBase IV, was that in fact, these are dB-IV .dbf's.  The
> difference is small, as noted below, between v. III and v. IV.
>
> gerry
>
> Peter Hopfgartner wrote:
>
>> Chris Hermansen wrote:
>>
>>> Peter;
>>>
>>> The canonical description of DBase files seems to be
>>>
>>> http://www.clicketyclick.dk/databases/xbase/format/
>>>
>>>
>>>
>> Well, first of all, I do not know which dBase version is targeted by
>> ArcGIS.
>>
>> Second, I doubt the exact values in
>> http://www.clicketyclick.dk/databases/xbase/format/data_types.html#DATA_TYPES.
>>
>>
>>  From our tests, both dbase III and dBase IV can handle text fields <= 254
>> characters (and not < 254).
>> Further, dBase III can handle numerics with <= 19 digits and not < 18
>> digits. dBase IV limits this to <= 20 digits.
>>
>> The above mentioned tool identifies ArcGIS generated files as dBase IV, in
>> clear conflict on what is said in the above mentioned Wikipedia article.
>>
>> Cheers,
>>
>> Peter
>>
>>> On Tue, 2009-12-01 at 17:28 +0100, Peter Hopfgartner wrote:
>>>
>>>
>>>> Mark Cave-Ayland wrote:
>>>>
>>>>
>>>>> Peter Hopfgartner wrote:
>>>>>
>>>>>
>>>>>
>>>>>> Dear PostGIS devels,
>>>>>>
>>>>>> since we right in the middle of comparing interoperability of shape
>>>>>> files between some FOSS programs and ArcGIS, we encoutered also the
>>>>>> following:
>>>>>>
>>>>>> gvSIG chokes on the Bigint as produced by pgsql2shp. Looking at ArcGIs
>>>>>> generated files, the max length for numbers is 19, compared to 20 for
>>>>>> integers and 32 for floating points as in pgsql2shp. This seems to be
>>>>>> confirmed by some Borland tools, when configured for dBase III+.
>>>>>>
>>>>>> Another limit seems to be that of text fields, that must be no longer
>>>>>> then 254. This is the maximum as given by ArcGIS and by the Borland tool.
>>>>>>
>>>>>> Another point is Boolean: ArcGIS seems to not allow the creation of
>>>>>> boolean fields and the Borland Tool ("Database Desktop") says that Booleans
>>>>>> have a length of 1.
>>>>>>
>>>>>> Regards,
>>>>>>
>>>>>> Peter
>>>>>>
>>>>>>
>>>>> Hi Peter,
>>>>>
>>>>> You've brought up some interesting points here. Can you actually
>>>>> clarify these changes with regard to parts of the official shapefile spec,
>>>>> or have they been found purely through experimentation?
>>>>>
>>>>>
>>>>> ATB,
>>>>>
>>>>> Mark.
>>>>>
>>>>>
>>>>>
>>>> Hi Mark,
>>>>
>>>> I do still have to figure out, if there are public specs for this. All
>>>> I've found is, that attributes should be in data base files which are in
>>>> dBase format (
>>>> http://www.esri.com/library/whitepapers/pdfs/shapefile.pdf). From the
>>>> analysis of the file (and Wikipedia:
>>>> http://en.wikipedia.org/wiki/Shapefile), it seems that this should be
>>>> dBase III. I do not have any evidence that there is a public spec for dBase
>>>> III.
>>>> So all we did is basically gather some experimental data, where ArcGIS
>>>> and gvSIG are our references. The first, because ESRI introduced the shape
>>>> file format and gvSIG, because it is the desktop environment that we
>>>> encourage our customers to use. Anyway, we have an old Borland/Inprise tool
>>>> ("Database Desktop") here for managing dBase files and used it for our
>>>> tests.
>>>>
>>>> Peter
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>> ------------------------------------------------------------------------
>>
>>
>> ------------------------------------------------------------------------
>>
>>
>> ------------------------------------------------------------------------
>>
>>
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