[sqlalchemy] Need help using PostGIS + GeoAlchemy
Hello,
I'm trying to use PostGIS with GeoAlchemy, being totally new to both.
According to available documentation and what I need (A point
representing longitude and latitude of row), I have
class PointOfInterest(Base):
__tablename__ = ...
...
geom = geoalchemy.GeometryColumn(Point(2))
To read from geom column, I apparently need:
poi = PointOfInterest()
lon = session.scalar(poi.geom.x)
lat = session.scalar(poi.geom.y)
And to set the value I need
poi.geom = geoalchemy.WKTSpatialElement(POINT({lon}
{lat}).format(lon, lat))
Of course, the above is possibly vulnerable for sql injections so I must
make sure lon and lat are really numbers.
But is there a simpler/safer/saner way to do both? Can I update the geom
column somehow to set only one value of the pair?
Also, I'm not quite sure how to query rows with X, Y being with N units
of a reference point X0, Y0?
Thanks.
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[sqlalchemy] Postgres migration issue
Hi
I usually use MySQL to develop on, however I need to work with Postgres for the
first time today so I fired it up. I have a routine which converts a non-SQL
database into the database of choice, converting its schema into a new table in
the target database using SQA, and then copies all the data in the source
database into the new SQL table.
That all worked fine into the Postgres+pg8000 database. My problem is when I
then attempt to open up a table again using auto reflection I get an error I've
never seen before, and I don't get how this can be, given the table was created
via sqlalchemy? The data looks fine in the table, and all columns are created
as I expected (converting to the correct Postrgres column types etc.
Error when I issue t = Table('my_table', meta, autoload=True) is; (sorry
about the screen shot, I'm working in a bad RDP client and can't cut/paste into
my Mac. :-(
So it appears to be having some problem in the reflection, but I can't see why
- I hope there is a setting in the connection or something I can do to fix this
up? I've never used Postgres before, so I'm groping in the dark.. From
Googling around, it appears that there is some issue with determining the
schema or some such, but it's all assuming I know a lot more about Postgres
than I do!
Cheers
Warwick
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[sqlalchemy] Re: Postgres migration issue
Hi
I usually use MySQL to develop on, however I need to work with Postgres for
the first time today so I fired it up. I have a routine which converts a
non-SQL database into the database of choice, converting its schema into a
new table in the target database using SQA, and then copies all the data in
the source database into the new SQL table.
That all worked fine into the Postgres+pg8000 database. My problem is when I
then attempt to open up a table again using auto reflection I get an error
I've never seen before, and I don't get how this can be, given the table was
created via sqlalchemy? The data looks fine in the table, and all columns
are created as I expected (converting to the correct Postrgres column types
etc.
Error when I issue t = Table('my_table', meta, autoload=True) is; (sorry
about the screen shot, I'm working in a bad RDP client and can't cut/paste
into my Mac. :-(
PastedGraphic-1.png
So it appears to be having some problem in the reflection, but I can't see
why - I hope there is a setting in the connection or something I can do to
fix this up? I've never used Postgres before, so I'm groping in the dark..
From Googling around, it appears that there is some issue with determining
the schema or some such, but it's all assuming I know a lot more about
Postgres than I do!
Cheers
Warwick
Further to the above - I looked into my code for the database cloning explained
above, to see how IT opened the table. It worked because I was still using the
same MetaData object, therefore the column defs were cached. The error happens
on a virgin MetaData object with autoload.
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Re: [sqlalchemy] Postgres migration issue
- Original Message -
Hi
I usually use MySQL to develop on, however I need to work with
Postgres for the first time today so I fired it up. I have a routine
which converts a non-SQL database into the database of choice,
converting its schema into a new table in the target database using
SQA, and then copies all the data in the source database into the
new SQL table.
That all worked fine into the Postgres+pg8000 database. My problem is
when I then attempt to open up a table again using auto reflection I
get an error I've never seen before, and I don't get how this can
be, given the table was created via sqlalchemy? The data looks fine
in the table, and all columns are created as I expected (converting
to the correct Postrgres column types etc.
Error when I issue t = Table('my_table', meta, autoload=True) is;
(sorry about the screen shot, I'm working in a bad RDP client and
can't cut/paste into my Mac. :-(
So it appears to be having some problem in the reflection, but I
can't see why - I hope there is a setting in the connection or
something I can do to fix this up? I've never used Postgres before,
so I'm groping in the dark.. From Googling around, it appears that
there is some issue with determining the schema or some such, but
it's all assuming I know a lot more about Postgres than I do!
Cheers
Warwick
Hi Warwick,
You are using pg8000 1.08 and PostgreSQL = 9.0. Upgrade to pg8000 1.09, it
fixes this issue (there are new PostgreSQL types introduced in version 9 which
pg8000 didn't know of in 1.08, and added in 1.09).
regards
--
David Moore
Senior Software Engineer
St. James Software
Email: dav...@sjsoft.com
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