BUG #6693: Potential Bug in rewriteManip.c

The following bug has been logged on the website:

Bug reference: 6693
Logged by: Ken Cheung
Email address: msrbugzilla(at)gmail(dot)com
PostgreSQL version: 9.1.3
Operating system: Linux
Description:

I observed a code clone in the following files. In these functions,
qry->resultRelation is computed differently but the comment above mentions
the same functionality. I wonder if this is a bug. Hope it helps.

function : ChangeVarNodes @ (file:
"postgresql-9.1.3/src/backend/rewrite/rewriteManip.c", line: 570)~608
context.rt_index = rt_index;
context.new_index = new_index;
context.sublevels_up = sublevels_up;

/*
* Must be prepared to start with a Query or a bare expression tree; if
* it's a Query, go straight to query_tree_walker to make sure that
* sublevels_up doesn't get incremented prematurely.
*/
if (node && IsA(node, Query))
{
Query *qry = (Query *) node;

/*
* If we are starting at a Query, and sublevels_up is zero, then we
* must also fix rangetable indexes in the Query itself --- namely
* resultRelation and rowMarks entries. sublevels_up cannot be zero
* when recursing into a subquery, so there's no need to have the same
* logic inside ChangeVarNodes_walker.
*/
if (sublevels_up == 0)
{
ListCell *l;

if (qry->resultRelation == rt_index)
qry->resultRelation = new_index;
foreach(l, qry->rowMarks)
{
RowMarkClause *rc = (RowMarkClause *) lfirst(l);

if (rc->rti == rt_index)
rc->rti = new_index;
}
}
query_tree_walker(qry, ChangeVarNodes_walker,
(void *) &context, 0);
}
else
ChangeVarNodes_walker(node, &context);

function : OffsetVarNodes @ (file:
"postgresql-9.1.3/src/backend/rewrite/rewriteManip.c", line: 402)~438
context.offset = offset;
context.sublevels_up = sublevels_up;

/*
* Must be prepared to start with a Query or a bare expression tree; if
* it's a Query, go straight to query_tree_walker to make sure that
* sublevels_up doesn't get incremented prematurely.
*/
if (node && IsA(node, Query))
{
Query *qry = (Query *) node;

/*
* If we are starting at a Query, and sublevels_up is zero, then we
* must also fix rangetable indexes in the Query itself --- namely
* resultRelation and rowMarks entries. sublevels_up cannot be zero
* when recursing into a subquery, so there's no need to have the same
* logic inside OffsetVarNodes_walker.
*/
if (sublevels_up == 0)
{
ListCell *l;

if (qry->resultRelation)
qry->resultRelation += offset;
foreach(l, qry->rowMarks)
{
RowMarkClause *rc = (RowMarkClause *) lfirst(l);

rc->rti += offset;
}
}
query_tree_walker(qry, OffsetVarNodes_walker,
(void *) &context, 0);
}
else
OffsetVarNodes_walker(node, &context);