On 05/21/2017 11:21 PM, ben4ever wrote:
if you refer to a table without a schema name, that's the schema it
will actually use
Yes, and that's the problem.
In my dialect's base.py I define the following method:
|
def _get_default_schema_name(self, connection):
return 'pub'
|
But the code sample mentioned in my first email yields the following
SELECT *without* prefixing the column and table names with "pub":
|
2017-05-18 16:26:51,151 INFO sqlalchemy.engine.base.Engine SELECT foo.f1
FROM foo
|
I noticed that there is no handling to retrieve the dialect's
default_schema_name from within the MetaData class in sql/schema.py but
like I said I just don't know whether this is intended for a reason.
OK, let me try again to explain.
if you refer to a table without a schema name, that's the schema **it**
> will actually use
"**it**" here means **the database, implicitly**.
That is, the default schema is what the SQLAlchemy dialect assumes will
be the effective schema name **when we do not state the schema name
explicitly**.
Example. On Postgresql, the default schema name is named "public".
Go to your Postgresql command line, run this statement:
psql > SELECT * FROM some_table
What schema is "some_table" in? Answer: "public". That's the default
schema. We *did not state this name*. It is *implicit*. SQLAlchemy
uses this name when you ask it a question like, "reflect the columns
from some_table". When it queries system catalogs, the default schema
is no longer implicit, we need it. We use get_default_schema to know
what that name is.
The only way SQLAlchemy states the schema name in the query is if:
a. you include it in the Table() definition, e.g. Table(...,
schema='myschema')
b. You include it in the MetaData so that it is inherited by the Table,
e.g. MetaData(schema='myschema')
c. you write your own dialect that explicitly injects the schema name
into SQL. If your database is unable to invoke SQL without all symbols
being schema-qualified, then you would need to do this. It's not clear
what the actual problem is.
On Friday, 19 May 2017 23:19:06 UTC+10, Mike Bayer wrote:
On 05/18/2017 08:42 PM, ben4ever wrote:
> I'm writing a Progress OpenEdge dialect and when experimenting
with the
> dialect's default_schema_name I noticed that it is not automatically
> used when creating a MetaData object without specifying a schema.
> Here is an example where the SELECT statement does not include the
> schema name specified in default_schema_name:
> |
> from urllib.parse import quote
>
> from sqlalchemy import create_engine, select, Table, Column,
Integer,
> MetaData
> import sqlalchemy_progress
>
> connect_string = 'progress:///?odbc_connect={}'.format(quote(
>
'DRIVER=progress;DB=bizcomm;HOST=hostname;PORT=1234;UID=admin'))
> engine = create_engine(connect_string, echo=True)
>
> metadata = MetaData()
> foo = Table('foo', metadata,
> Column('f1', Integer),
> Column('f2', Integer))
>
> print(engine.connect().execute(
> select([foo.c.f1])
> ).fetchall())
> |
>
> Is this the intended behaviour?
yes. the "default" schema means, the *database's* default schema.
that is, if you refer to a table without a schema name, that's the
schema it will actually use.
>
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