Thank you for the response,
I ran the same data with sqlite, and this is what I get with
db.describe -c:
[sqlite db]
GRASS 6.4.0 (spearfish60):~ > db.describe -c mysoils
ncols: 5
nrows: 54
Column 1: cat:INTEGER:20
Column 2: label:CHARACTER:13
Column 3: id:CHARACTER:1
Column 4: shortname:CHARACTER:1
Column 5: longname:CHARACTER:1
GRASS 6.4.0 (spearfish60):~ > db.describe -c soils_legend
ncols: 3
nrows: 55
Column 1: id:CHARACTER:1
Column 2: shortname:CHARACTER:1
Column 3: longname:CHARACTER:1
GRASS 6.4.0 (spearfish60):~ >
- and there is no truncation of data after v.db.join,
while
[mysql db]
GRASS 6.4.0 (spearfish60):~ > db.describe -c mysoils
ncols: 5
nrows: 54
Column 1: cat:INTEGER:11
Column 2: label:CHARACTER:13
Column 3: id:CHARACTER:1
Column 4: shortname:CHARACTER:1
Column 5: longname:CHARACTER:1
GRASS 6.4.0 (spearfish60):~ > db.describe -c soils_legend
ncols: 3
nrows: 55
Column 1: id:CHARACTER:255
Column 2: shortname:CHARACTER:255
Column 3: longname:CHARACTER:255
GRASS 6.4.0 (spearfish60):~ >
- truncates the data in joined columns
I do not have a suggestion for an improved script - not up to that
yet. The mysql db seems to be more strict as to the column variable
length definition. As you point out, the definition is ignored and
data carried over differently in sqlite and mysql. Hope that someone
can take this up.
Thanks, Jon
On 13.10.2010, at 20:23, Micha Silver wrote:
On 10/12/2010 12:01 PM, Jon Eiriksson wrote:
Hi,
I have a truncation problem with v.db.join. This has been raised
before -
([GRASS-user] Re: grass v.db.join
Gary Nobles
Fri, 12 Mar 2010 11:11:26 -0800)
- but I have not seen a solution. I have tried my own data, the
spearfish60 example data, and the example in Neteler and Mitasova's
book.
The new data columns are apparently defined as 1 character long,
and the
data become truncated accordingly, much against my intention. I use
mysql.
I can see why this is happening. But I'm not sure what the correct
solution might be. v.db.join is a wrapper around db.describe and
v.db.addcol. When I query an sqlite database connection here's what
the output looks like:
db.describe -c bike_rides2
ncols: 8
nrows: 17
Column 1: cat:INTEGER:20
Column 2: name:CHARACTER:80
Column 3: number:INTEGER:20
Column 4: comment:CHARACTER:80
Column 5: descriptio:CHARACTER:80
Column 6: source:CHARACTER:80
Column 7: url:CHARACTER:80
The output format is obviously:
"Column num:column name:column type:column size".
One line from the v.db.join script uses grep and cut to get the
column names and the next line gets the column types like so:
db.describe -c bike_rides2 | grep '^Column' | cut -d ':' -f 3
INTEGER
CHARACTER
INTEGER
CHARACTER
CHARACTER
CHARACTER
CHARACTER
So the column size is actually ignored.
Next, in the script the above output is used by v.db.addcol to
create the new columns in the joined vector. So all new character
columns are created as a single char and the actual length is never
used.
Questions:
Is the db.describe output the same for all db drivers?
Any suggestions how to fix this as a script?
Or better, just convert to python?
Thanks,
Micha
--
Micha Silver
Arava Development Co. +972-52-3665918
http://www.surfaces.co.il
-------------------------------------------------------------------
Jon Eiriksson, Research Professor,
Earth Science Institute, University of Iceland,
Askja, Sturlugata 7,
IS-101 Reykjavik, Iceland.
Tel +354 525 44 75
Fax +354 525 44 99
Email [email protected]
Web http://www.raunvis.hi.is/~jeir/
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