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Problem in AlterTableAddConstraint?

From: Philip Warner <pjw(at)rhyme(dot)com(dot)au>
To: pgsql-hackers(at)postgresql(dot)org
Subject: Problem in AlterTableAddConstraint?
Date: 2000-11-28 15:49:11
Message-ID: 3.0.5.32.20001129024911.02c4e6d0@mail.rhyme.com.au (view raw or flat)
Thread:
Lists: pgsql-hackers
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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