On Thu, 2007-12-13 at 22:23 -0800, Neil Conway wrote:
> On Thu, 2007-12-13 at 22:06 -0500, Tom Lane wrote:
> > I guess that on purely philosophical grounds, it's not an unreasonable
> > behavior. For example, "LIMIT n" means "output at most n tuples",
> > not "output exactly n tuples". So when it outputs no tuples in the face
> > of a negative limit, it's meeting its spec.
>
> If "LIMIT n" means "emit at most n tuples", then a query that produces 0
> rows with n < 0 is arguably violating its spec, since it has produced
> more tuples than the LIMIT specified (0 > n). Interpreted this way, no
> result set can be consistent with a negative limit, so I'd vote for
> throwing an error.
I even found an existing, unused error message called
ERRCODE_INVALID_LIMIT_VALUE
so here's a patch.
--
Simon Riggs
2ndQuadrant http://www.2ndQuadrant.com
Index: src/backend/executor/nodeLimit.c
===================================================================
RCS file: /home/sriggs/pg/REPOSITORY/pgsql/src/backend/executor/nodeLimit.c,v
retrieving revision 1.32
diff -c -r1.32 nodeLimit.c
*** src/backend/executor/nodeLimit.c 15 Nov 2007 21:14:34 -0000 1.32
--- src/backend/executor/nodeLimit.c 14 Dec 2007 14:34:22 -0000
***************
*** 75,81 ****
/*
* Check for empty window; if so, treat like empty subplan.
*/
! if (node->count <= 0 && !node->noCount)
{
node->lstate = LIMIT_EMPTY;
return NULL;
--- 75,81 ----
/*
* Check for empty window; if so, treat like empty subplan.
*/
! if (node->count = 0 && !node->noCount)
{
node->lstate = LIMIT_EMPTY;
return NULL;
***************
*** 246,252 ****
{
node->offset = DatumGetInt64(val);
if (node->offset < 0)
! node->offset = 0;
}
}
else
--- 246,254 ----
{
node->offset = DatumGetInt64(val);
if (node->offset < 0)
! ereport(ERROR,
! (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! errmsg("OFFSET must not be negative")));
}
}
else
***************
*** 271,277 ****
{
node->count = DatumGetInt64(val);
if (node->count < 0)
! node->count = 0;
node->noCount = false;
}
}
--- 273,281 ----
{
node->count = DatumGetInt64(val);
if (node->count < 0)
! ereport(ERROR,
! (errcode(ERRCODE_INVALID_LIMIT_VALUE),
! errmsg("LIMIT must not be negative")));
node->noCount = false;
}
}
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