Re: python patch - Mailing list pgsql-hackers

On Sun, 2002-08-11 at 21:15, Christopher Kings-Lynne wrote:
> > Not a problem.  I would rather them be correct.
> >
> > Worth noting that the first patch is what attempts to fix the long ->
> > int overflow issue.  The second patch attempts to resolve "attisdropped"
> > column use issues with the python scripts.  The third patch addresses
> > issues generated by the implicate to explicate use of "cascade".
> >
> > I assume your reservations are only with the second patch and not the
> > first and third patches?
>
> Correct.  I'm pretty sure you don't need to exclude attisdropped from the
> primary key list because all it's doing is finding the column that a primary
> key is over and that should never be over a dropped column.  I can't
> remember what you said the second query did?


Hmmm.  Sounds okay but I'm just not sure that holds true (as I
previously stated, I'm ignorant on the topic).  Obviously I'll defer to
you on this.

Here's the queries and what they do:


From pg.py:
Used to locate primary keys -- or so the comment says.  It does create a
dictionary of keys and attribute values for each returned row so I
assume it really is attempting to do something of the like.

SELECT pg_class.relname, pg_attribute.attname
FROM pg_class, pg_attribute, pg_index
WHERE pg_class.oid = pg_attribute.attrelid AND pg_class.oid = pg_index.indrelid AND pg_index.indkey[0] =
pg_attribute.attnumAND pg_index.indisprimary = 't' AND pg_attribute.attisdropped = 'f' ; 

So, everyone is in agreement that any attribute which is indexed as a
primary key will never be able to have attisdtopped = 't'?

According to the code:
SELECT pg_attribute.attname, pg_type.typname
FROM pg_class, pg_attribute, pg_type
WHERE pg_class.relname = '%s' ANDpg_attribute.attnum > 0 ANDpg_attribute.attrelid = pg_class.oid
ANDpg_attribute.atttypid= pg_type.oid ANDpg_attribute.attisdropped = 'f' ; 

is used to obtain all attributes (column names) and their types for a
given table ('%s').  It then attempts to build a column/type cache.  I'm
assuming that this really does need to be there.  Please correct
accordingly.


From syscat.py:
SELECT bc.relname AS class_name,ic.relname AS index_name, a.attname
FROM pg_class bc, pg_class ic, pg_index i, pg_attribute a
WHERE i.indrelid = bc.oid AND i.indexrelid = bc.oidAND i.indkey[0] = a.attnum AND a.attrelid = bc.oidAND i.indproc =
'0'::oidAND a.attisdropped = 'f'ORDER BY class_name, index_name, attname ; 

According to the nearby documentation, it's supposed to be fetching a
list of "all simple indicies".  If that's the case, is it safe to assume
that any indexed column will never have attisdropped = 't'?  If so, we
can remove that check from the file as well.  Worth pointing out, this
is from syscat.py, which is sample source and not used as actual
interface.  So, worse case, it would appear to be redundant in nature
with no harm done.

This should conclude the patched items offered in the second patch.

What ya think?

Thanks,Greg