Re: Problem in AlterTableAddConstraint?

Should be fixed now.  I had sent a patch in a while ago about it
and the code does seem to do an extra step now which gets the length
of the index and compares it to the length of the attribute list.

On Mon, 22 Jan 2001, Bruce Momjian wrote:

> 
> Can anyone comment on this?
> 
> > 
> > Browsing through backend/commands/command.c I noticed the following code:
> > 
> >     if (indexStruct->indisunique)
> >     {
> >         List       *attrl;
> > 
> >         /* go through the fkconstraint->pk_attrs list */
> >         foreach(attrl, fkconstraint->pk_attrs)
> >         {
> >             Ident *attr=lfirst(attrl);
> >             found = false;
> >             for (i = 0; i < INDEX_MAX_KEYS && indexStruct->indkey[i] != 0;
> > i++)
> >             {
> >                 int pkattno = indexStruct->indkey[i];
> >                 if (pkattno>0)
> >                 {
> >                     char *name = NameStr(rel_attrs[pkattno-1]->attname);
> >                     if (strcmp(name, attr->name)==0)
> >                     {
> >                         found = true;
> >                         break;
> >                     }
> >                 }
> >             }
> >             if (!found)
> >                 break;
> >         }
> >     }
> > 
> > which is (I think) supposed to be checking for a unique index on the FK
> > fields in the referenced table.
> > 
> > Unfortunately, my reading of this code suggests it is doing the following:
> > 
> >     for each column in the FK
> > 
> >         see if we can find the column in the index
> >         if not, then die
> > 
> >     next FK column
> > 
> > The problem with this is that it needs to ensure a 1:1 match between
> > columns for the UNIQUE constraint requirement to be satisfied...I think.
> > 
> > To give an example,
> > 
> >     create table c2(f1 integer, f2 integer, unique(f1,f2));
> >     create table c1(f1 integer, f2 integer, foreign key(f1) references
> > c2(f1));
> > 
> > is allowed with current sources.
> > 
> > I'd guess that adding code to ensure the column lists are the same size
> > would fix the problem.
> > 
> > 
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> 
> 
> -- 
>   Bruce Momjian                        |  http://candle.pha.pa.us
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