On 2022-02-12 20:12:02 -0500, Mladen Gogala wrote: > On 2/12/22 19:11, Andreas 'ads' Scherbaum wrote: > > The complaint is not about complex queries, or CTEs, or Joins. This is > about simple queries where a user wants to discover - surf - the database > and look into specific tables, but exclude certain columns. More > specifically, > this is when the user types in interactive queries. > > There is already something very similar to what you are describing: > > https://www.psycopg.org/docs/cursor.html I'm not sure whether the PEP 249 notion of a cursor is relevant here. That's quite Python specific and at least one step removed from the SQL concept of a cursor. > Each cursor has its description, which consists of the column descriptions. Not really. While description is a property of the cursor object in Python, it always describes the last query executed within that cursor: % python3 Python 3.8.10 (default, Nov 26 2021, 20:14:08) [GCC 9.3.0] on linux Type "help", "copyright", "credits" or "license" for more information. >>> import psycopg2 >>> db = psycopg2.connect("") >>> csr = db.cursor() >>> csr.description (no output) >>> csr.execute("select * from t1 natural join t2") >>> csr.description (Column(name='a', type_code=23), Column(name='b', type_code=23), Column(name='c', type_code=23)) >>> csr.fetchall() [(1, 2, 11), (1, 2, 10)] >>> csr.description (Column(name='a', type_code=23), Column(name='b', type_code=23), Column(name='c', type_code=23)) (we can still refer to the description even after fetching all the data) >>> csr.execute("select x from t1 natural join t2") Traceback (most recent call last): File "<stdin>", line 1, in <module> psycopg2.errors.UndefinedColumn: column "x" does not exist LINE 1: select x from t1 natural join t2 >>> csr.description (no output again after a failed query) > Basically, it's like doing \d on a cursor. Unfortunately, it's not interactive, > one has to do some pythong programming in order do to that. Unfortunately, it > is not possible to just "describe the cursor", the description becomes > available after the "execute" call. Yup, as demonstrated above. Which means that you have to actually execute the query. Which is something that a should not happen as a side effect of editing the query. hp -- _ | Peter J. Holzer | Story must make more sense than reality. |_|_) | | | | | hjp@xxxxxx | -- Charles Stross, "Creative writing __/ | http://www.hjp.at/ | challenge!"
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