Assign special dbf to shapefile

[Sean Gillies]

Steve,

Moving to PostGIS wouldn't be as hard as you think.  There are many of
us who will be glad to help you out.  Another better possibility is
trying to light a fire under the MapServer/MySQL developer so that you
can move your shapes into MySQL.  I'm not even talking about a
PostGIS-ish library for MySQL, just putting features in as a blob that
can be extracted and converted to MapServer shapes for rendering, and
spatial indexes.

Sean

On Jan 7, 2005, at 12:44 PM, Stephen Woodbridge wrote:

> The issue is that you can not do joins to classify data when drawing
> maps if you use shapefiles. JOIN works fine with queries.
>
> I have all the tiger data in shapefile (16 GB of data) and all of the
> Census Summary File 1 and 3 data in MySQL (101 GB, plus a lot more for
> indexes). I would like to draw thematic maps of the US based on these
> datasets. Moving all this data to PostGIS, is possible but a huge task,
> not to mention I would have to learn a new DB and how to administer it.
> I will probably end up doing this at some point when the need is
> higher.
>
> Meanwhile, this is basically what others are trying to do also. It is
> just a HUGE step to move from shapefiles and MySQL to managing
> everything in PostGIS.
>
> Still hoping Steve Lime will take pity on me,
> but not holding my breath.
>    -Steve
>
> Ken Lord wrote:
>> This definately calls for PostGIS, and I'm sure it would process the
>> request much faster.
>>
>> But,
>>
>> Why not use the join object in mapserver?
>>
>> http://mapserver.gis.umn.edu/doc44/mapfile-reference.html#join
>>
>> Or is this join system, that was broken i think after mapserver 3.4,
>> still not functional? ... and if it is still not functional why have
>> the instructions remained in the current documentation for the last 2
>> years+ ... since at least mapserver 3.6?
>>
>> There is another option:
>>
>> Don't join the data on-the-fly. Instead when the user queries the
>> airport, have a link parsed in the query results that when followed
>> displays the attribute data you want based on the query results
>> returned. ... A little ASP works wonders here to take a mapserver
>> query result and query another database with it.
>>
>> Cheers,
>> Ken
>>
>> On Fri, 7 Jan 2005 10:22:02 -0500, Stephen Woodbridge
>> <woodbri at swoodbridge.com> wrote:
>>
>>> The only way that I know of to do runtime joins in mapserver is to
>>> use
>>> PostGIS. You might be able to do something with gdal, but I think it
>>> is
>>> very slow.  I have requested support for runtime shapefile joins to
>>> either DBF or MySQL multiple times and nothing has happened in that
>>> direction. Basically, it would be very slow because for each object
>>> in
>>> the shapefile, you would have to scan the whole DBF file, because
>>> there
>>> are no indexes support for DBF files, or the developers would have to
>>> build DBF indexing support into mapserver. For Mysql, you could index
>>> the columns, but you would still need to make a separate query for
>>> every
>>> object in the shapefile.
>>>
>>> In PostGIS, since you have all the data in the database to start with
>>> you can make one query for the layer and do the join in that query,
>>> then
>>> you only have to fetch back the objects to render.
>>>
>>> -Steve W.
>>>
>>> Holger Floerke wrote:
>>>
>>>> Hi Jacob,
>>>>
>>>>
>>>>
>>>>> Why would you not want to join them?
>>>>
>>>> If the information I would like to present is evaluated at runtime,
>>>> I have
>>>> to produce a full set of ".shp", ".dbf", "sbx", "sbn", and ".shx"
>>>> files. The
>>>> shapes always stays the same, but the data is extracted from a
>>>> database on a
>>>> user's query. I would like to save space by not copying the shape
>>>> information every time.
>>>>
>>>>
>>>>
>>>>> unless if you created a join on a dbf, and accessed it separately.
>>>>
>>>> Is it possible to join external data sources (one or more dbf-files
>>>> or
>>>> oci-sources) to shape files at runtime with the mapserver-api?
>>>>
>>>> HolgeR
>>>>
>>>>
>>>> Jacob Delfos schrieb:
>>>>
>>>>
>>>>
>>>>> Holger,
>>>>>
>>>>> Correct me if I'm wrong, but that would be redefining the
>>>>> definition of
>>>>> a shapefile. As far as I know, a "shapefile" is not the .shp file,
>>>>> but
>>>>> the collection of ".shp", ".dbf", "sbx", "sbn", and ".shx" files. I
>>>>> think you'd have to seriously hack the source of mapserver to do
>>>>> that,
>>>>> unless if you created a join on a dbf, and accessed it separately.
>>>>>
>>>>> Why would you not want to join them? If you have access to MS
>>>>> Excel, it
>>>>> would be as simple as copying a column across. No doubt other
>>>>> software
>>>>> can do the same thing. You would have access to both attributes in
>>>>> one
>>>>> shapefile. What is the actual problem that causes you not to want
>>>>> to
>>>>> have two shapefiles, and not to want to join the attributes?
>>>>>
>>>>> regards,
>>>>>
>>>>> Jacob
>>>>>
>>>>>
>>>>> -----Original Message-----
>>>>> From: UMN MapServer Users List
>>>>> To: MAPSERVER-USERS at LISTS.UMN.EDU
>>>>> Sent: 1/7/2005 9:03 PM
>>>>> Subject: [UMN_MAPSERVER-USERS] Assign special dbf to shapefile
>>>>>
>>>>> Hi all,
>>>>>
>>>>> am I able to assign a special dbf-file to a shape file? For example
>>>>> rendering the 'airports.shp', but using data from
>>>>> 'airports_passengers.dbf'
>>>>> and not from 'airports.dbf' (ensuring the correct order for the
>>>>> shape-information-mapping). Or another example, render some area
>>>>> shapes
>>>>> on
>>>>> the one hand with popuplation data and on the other hand with
>>>>> unemployment
>>>>> data without integrating both data sets into the dbf of the shape
>>>>> file
>>>>> and
>>>>> without producing two different shape-files. I use php-mapscript
>>>>> and
>>>>> mapserver 4.4.
>>>>>
>>>>> HolgeR
>>>>>
>>>>
>>>>
>>
>