我正在尝试建立我的第一个Postgres数据库，但是对于为什么在一个模式中启用Postgis然后在另一个模式中使用Postgis时遇到的问题感到非常困惑。
我将Google Cloud SQL与Postgres v12结合使用。 我正在通过Cloud SQL代理连接，并且已经通过pgAdmin4和Jupyter Notebook（SQLAlchemy）连接到服务器。
我的目标是通过geopandas将充满点的shapefile写入数据库的表中。
基于this thread，我试图将postgis安装到一个单独的模式中，同时创建一些其他不同的模式来实际存储我的数据。 我正在用geopandas打开shapefile，然后使用.to_postgis（）尝试将shapefile的内容保存到我的一种数据模式中的新表中。这总是失败。
但是，如果我尝试将地理数据框写入扩展架构，则可以正常工作。这使我认为search_path出了点问题，但不知道是怎么回事。 我正在按照建议的here设置搜索路径。 我尝试了各种方法来设置search_path，但我认为我对它的功能和工作原理缺乏基本了解。
这是工作流程：
SQL：
CREATE SCHEMA extensions;
CREATE SCHEMA geodata;
ALTER DATABASE mydb SET search_path = geodata,extensions,public;
CREATE EXTENSION postgis SCHEMA extensions;
然后在jupyter笔记本中：
# imports
from sqlalchemy import create_engine
import geopandas as gpd
# connect to database
dbschema = 'geodata' # note, if I change this to 'extensions' it works
engine = create_engine('postgresql+psycopg2://postgres:<password>@localhost:5432/mydb', connect_args={'options': '-csearch_path={}'.format(dbschema)})
# Open shapefile
gdf = gpd.read_file(r"C:\path\to\shapefile.shp")
# Attempt to write shapefile to postgis
gdf.to_postgis(name = 'geotable', con = engine)
这是我得到的错误：
UndefinedObject Traceback (most recent call last)
~\Anaconda3\envs\rasterio\lib\site-packages\sqlalchemy\engine\base.py in _execute_context(self, dialect, constructor, statement, parameters, *args)
1275 if not evt_handled:
-> 1276 self.dialect.do_execute(
1277 cursor, statement, parameters, context
~\Anaconda3\envs\rasterio\lib\site-packages\sqlalchemy\engine\default.py in do_execute(self, cursor, statement, parameters, context)
592 def do_execute(self, cursor, statement, parameters, context=None):
--> 593 cursor.execute(statement, parameters)
594
UndefinedObject: type "geometry" does not exist
LINE 7: geometry geometry(POINT,28354)
^
The above exception was the direct cause of the following exception:
ProgrammingError Traceback (most recent call last)
<ipython-input-6-a0dc69a1128e> in <module>
1 from geoalchemy2 import Geometry
----> 2 gdf.to_postgis(name = 'vines', con = engine, if_exists = 'replace')
~\Anaconda3\envs\rasterio\lib\site-packages\geopandas\geodataframe.py in to_postgis(self, name, con, schema, if_exists, index, index_label, chunksize, dtype)
1095 >>> gdf.to_postgis("my_table", engine)
1096 """
-> 1097 geopandas.io.sql._write_postgis(
1098 self, name, con, schema, if_exists, index, index_label, chunksize, dtype
1099 )
~\Anaconda3\envs\rasterio\lib\site-packages\geopandas\io\sql.py in _write_postgis(gdf, name, con, schema, if_exists, index, index_label, chunksize, dtype)
390 with con.begin() as connection:
391
--> 392 gdf.to_sql(
393 name,
394 connection,
~\Anaconda3\envs\rasterio\lib\site-packages\pandas\core\generic.py in to_sql(self, name, con, schema, if_exists, index, index_label, chunksize, dtype, method)
2651 from pandas.io import sql
2652
-> 2653 sql.to_sql(
2654 self,
2655 name,
~\Anaconda3\envs\rasterio\lib\site-packages\pandas\io\sql.py in to_sql(frame, name, con, schema, if_exists, index, index_label, chunksize, dtype, method)
510 )
511
--> 512 pandas_sql.to_sql(
513 frame,
514 name,
~\Anaconda3\envs\rasterio\lib\site-packages\pandas\io\sql.py in to_sql(self, frame, name, if_exists, index, index_label, schema, chunksize, dtype, method)
1314 dtype=dtype,
1315 )
-> 1316 table.create()
1317 table.insert(chunksize, method=method)
1318 if not name.isdigit() and not name.islower():
~\Anaconda3\envs\rasterio\lib\site-packages\pandas\io\sql.py in create(self)
653 raise ValueError(f"'{self.if_exists}' is not valid for if_exists")
654 else:
--> 655 self._execute_create()
656
657 def _execute_insert(self, conn, keys, data_iter):
~\Anaconda3\envs\rasterio\lib\site-packages\pandas\io\sql.py in _execute_create(self)
639 # Inserting table into database, add to MetaData object
640 self.table = self.table.tometadata(self.pd_sql.meta)
--> 641 self.table.create()
642
643 def create(self):
~\Anaconda3\envs\rasterio\lib\site-packages\sqlalchemy\sql\schema.py in create(self, bind, checkfirst)
925 if bind is None:
926 bind = _bind_or_error(self)
--> 927 bind._run_visitor(ddl.SchemaGenerator, self, checkfirst=checkfirst)
928
929 def drop(self, bind=None, checkfirst=False):
~\Anaconda3\envs\rasterio\lib\site-packages\sqlalchemy\engine\base.py in _run_visitor(self, visitorcallable, element, **kwargs)
1654
1655 def _run_visitor(self, visitorcallable, element, **kwargs):
-> 1656 visitorcallable(self.dialect, self, **kwargs).traverse_single(element)
1657
1658
~\Anaconda3\envs\rasterio\lib\site-packages\sqlalchemy\sql\visitors.py in traverse_single(self, obj, **kw)
143 meth = getattr(v, "visit_%s" % obj.__visit_name__, None)
144 if meth:
--> 145 return meth(obj, **kw)
146
147 def iterate(self, obj):
~\Anaconda3\envs\rasterio\lib\site-packages\sqlalchemy\sql\ddl.py in visit_table(self, table, create_ok, include_foreign_key_constraints, _is_metadata_operation)
825 include_foreign_key_constraints = None
826
--> 827 self.connection.execute(
828 # fmt: off
829 CreateTable(
~\Anaconda3\envs\rasterio\lib\site-packages\sqlalchemy\engine\base.py in execute(self, object_, *multiparams, **params)
1009 )
1010 else:
-> 1011 return meth(self, multiparams, params)
1012
1013 def _execute_function(self, func, multiparams, params):
~\Anaconda3\envs\rasterio\lib\site-packages\sqlalchemy\sql\ddl.py in _execute_on_connection(self, connection, multiparams, params)
70
71 def _execute_on_connection(self, connection, multiparams, params):
---> 72 return connection._execute_ddl(self, multiparams, params)
73
74 def execute(self, bind=None, target=None):
~\Anaconda3\envs\rasterio\lib\site-packages\sqlalchemy\engine\base.py in _execute_ddl(self, ddl, multiparams, params)
1066 else None,
1067 )
-> 1068 ret = self._execute_context(
1069 dialect,
1070 dialect.execution_ctx_cls._init_ddl,
~\Anaconda3\envs\rasterio\lib\site-packages\sqlalchemy\engine\base.py in _execute_context(self, dialect, constructor, statement, parameters, *args)
1314
1315 except BaseException as e:
-> 1316 self._handle_dbapi_exception(
1317 e, statement, parameters, cursor, context
1318 )
~\Anaconda3\envs\rasterio\lib\site-packages\sqlalchemy\engine\base.py in _handle_dbapi_exception(self, e, statement, parameters, cursor, context)
1508 util.raise_(newraise, with_traceback=exc_info[2], from_=e)
1509 elif should_wrap:
-> 1510 util.raise_(
1511 sqlalchemy_exception, with_traceback=exc_info[2], from_=e
1512 )
~\Anaconda3\envs\rasterio\lib\site-packages\sqlalchemy\util\compat.py in raise_(***failed resolving arguments***)
180
181 try:
--> 182 raise exception
183 finally:
184 # credit to
~\Anaconda3\envs\rasterio\lib\site-packages\sqlalchemy\engine\base.py in _execute_context(self, dialect, constructor, statement, parameters, *args)
1274 break
1275 if not evt_handled:
-> 1276 self.dialect.do_execute(
1277 cursor, statement, parameters, context
1278 )
~\Anaconda3\envs\rasterio\lib\site-packages\sqlalchemy\engine\default.py in do_execute(self, cursor, statement, parameters, context)
591
592 def do_execute(self, cursor, statement, parameters, context=None):
--> 593 cursor.execute(statement, parameters)
594
595 def do_execute_no_params(self, cursor, statement, context=None):
ProgrammingError: (psycopg2.errors.UndefinedObject) type "geometry" does not exist
LINE 7: geometry geometry(POINT,28354)
^
[SQL:
CREATE TABLE geotable (
id BIGINT,
geometry geometry(POINT,28354)
)
]
(Background on this error at: http://sqlalche.me/e/13/f405)
答案 0 :(得分：2)
问题在于，当您连接到PostgreSQL时，您正在显式设置search_path。这会覆盖用ALTER DATABASE设置的值。
您有两个选择：
正确设置search_path：
dbschema = 'geodata,extensions,public'
通过默认设置保留不设置options中的create_engine参数。
由于您很努力地设置一个很好的默认值，因此我会选择第二个选项。
我个人使用public模式进行扩展（从CREATE撤消了PUBLIC特权之后），但是您可能会选择完全删除该模式。