[postgis-users] ESRI Shapes from database

Lee Keel lee.keel at uai.com
Wed Oct 17 07:28:04 PDT 2007


From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Obe,
Sent: Wednesday, October 17, 2007 7:42 AM
To: PostGIS Users Discussion
Subject: RE: [postgis-users] ESRI Shapes from database




Just wondering what your example bytea looks like that you are trying to
convert that is giving you problems.  Normally I would think what you are
doing below should work (and I have tried some simple examples and they work
- but I don't work with bytea so what do I know.)  


So perhaps whatever your bytea is returning is out of range of float and is
not actually what you think it is like you have a terminator byte in there
or something causing the problems.


Other thought is if you could get the string representation of your xcoord
without casting to float,  since in the next line your float is going to be
internally recast as a string to do this  sb := sb || '(' || xCoord || ' '
|| yCoord; 



Hope that helps,







The reason that I can't go from the string representation is that the 8bytes
used from the bytea are an encoding that contain information about where to
place the decimal and the digits on both sides of the decimal.  So I need to
cast to a float, then back to a string to get the complete point.  I am very
curious as to the examples you got working.  Could you please post what you
had so I can take a look at what I am doing wrong.  Here is what I have, I
am just not sure how to take a hex string and convert it to float:


(encode(substring(esri_shape from cnt for 8), 'hex'))






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