Re: Problem in AlterTableAddConstraint?

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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