Re: [PyGreSQL] DB API-2.0 + copy from stdin

[Christopher Sean Hilton]

On Sep 24, 2008, at 4:24 AM, Christoph Zwerschke wrote:

I think that's a reasonable suggestion. If I understand you right, then

all we need to do is:

1) Add a parameter "db" to the pg.DB class. If it is set to None (the

connection will be used. (I suggest the name "db" instead of "cnx"
because the name of the corresponding attribute is already "db".)

2) Add an attribute "_closeable" to pg.DB which will be set when the
instance has not been created with a preestablihed connection. The

_closeable is false.

3) Add a pdb.pgdbCnx method for getting a classic pg.DB instance.
Maybe we don't even need that, since getting it is as easy as

you're leaving the DB-API2 world if you're using this feature.

An additional suggestion from my site is making the (pseudo) private
attributes of pg.DB public, as we did with the private attributes in
pgdb. A single underscore should suffice to indicate that these should

default), then a new connection will be established, otherwise the given close() and reopen() methods of pg.DB will then raise an exception when DB(db=con._cnx) when con is a pgdb connection. So the pgdb module would normally not need to import the pg module, and it would be clearer that not be used from outside unless really necessary as in cases like this.

The new usage example looks like this.

#! /usr/bin/env python



import pg, pgdb

dbApiDb = pgdb.connect('message_board')
myCursor = dbApiDb.cursor()
myCursor.execute("CREATE TEMPORARY TABLE new_author(..."))

classicDb = pg.DB(dbApiDb._cnx)
classicDb.query("COPY new_author FROM stdin")
for row in data:
    classicDb.putline("\t".join(row) + "\n")
classicDb.putline("\\.\n")
classicDb.endcopy()

del classicDb
...
del myCursor
dbApiDb.commit()
dbApiDb.close()

I'm attaching a patch that implements 1 and 2 on the latest version of pg.py that I could get from the CVS web front end. For 3 I'm tempted to implement a method anyhow for exactly the reason that you said, people should be very clear about which interface that they are using. My style is to use DB-API wherever possible and use the older interfaces only where SQL doesn't properly specify tools for an application's needs (e.g. PostgreSQL's COPY table... or MySQL's LOAD DATA INFILE..). It looks like the original code used TABs for indenting. I preserved that but to do it I had to untab and then retab the whole thing in emacs. That produced a harmless? whitespace difference in the new Decimal code as well as a couple of similarly harmless changes in some of the doc strings. """Example code to that primarily uses a DB-API 2.0 interface to postgresql but drops town to the classic interface to load a temporary table. This is useful when you have a lot of data to load and multiple INSERTS are too slow."""

pg.py.patch
Description: Binary data

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Chris Hilton e: chris|at|vindaloo| dot|com "The pattern juggler lifts his hand; The orchestra begin. As slowly turns the grinding wheel in the court of the crimson king." -- Ian McDonald / Peter Sinfield