A bug was introduced a while ago by this patch:
> commit 447f7364dd7227a32b58a2aff24f587dd7d7051a
> Author: Tom Lane <[EMAIL PROTECTED]>
> Date: Sat Apr 12 23:14:21 2008 +0000
>
> Create new routines systable_beginscan_ordered,
systable_getnext_ordered,
> systable_endscan_ordered that have API similar to
systable_beginscan etc
> (in particular, the passed-in scankeys have heap not index attnums),
> but guarantee ordered output, unlike the existing functions. For
the moment
> these are just very thin wrappers around
index_beginscan/index_getnext/etc.
> Someday they might need to get smarter; but for now this is just
a code
> refactoring exercise to reduce the number of direct callers of
index_getnext
> in preparation for changing that function's API.
>
> In passing, remove index_getnext_indexitem, which has been dead
code for
> quite some time, and will have even less use than that in the
presence
> of run-time-lossy indexes.
You get this assertion failure:
TRAP: FailedAssertion("!(key[i].sk_attno ==
indexRelation->rd_index->indkey.values[i])", File: "genam.c", Line: 363)
with this test case:
CREATE DATABASE vdb WITH ENCODING = 'SQL_ASCII';
\c vdb
CREATE TABLE xtable(x text);
-- we must do this because otherwise the strings are too compressible
and don't
-- get toasted externally
ALTER TABLE xtable ALTER x SET STORAGE EXTERNAL;
---retrieving a substr(toasteddatum,x,y) where where x .. x+y spans two
chunks.
INSERT INTO xtable (SELECT REPEAT('ABCDEFGHIJ',400));
SELECT substr(x,1000,2000) from xtable ;
Basically, this comment and code in genam.c:
! /*
! * Change attribute numbers to be index column numbers.
! *
! * This code could be generalized to search for the index key
numbers
! * to substitute, but for now there's no need.
! */
for (i = 0; i < nkeys; i++)
{
! Assert(key[i].sk_attno ==
irel->rd_index->indkey.values[i]);
! key[i].sk_attno = i + 1;
}
is wrong, because it assumes that there's only one scankey per index
column, but that's not true for toast_fetch_datum_slice(), which uses
two scankeys for the chunkid, to fetch a range. Attached is a patch to
fix that, as suggested in the comment. Comments? I'll apply if not..
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
*** src/backend/access/index/genam.c
--- src/backend/access/index/genam.c
***************
*** 194,209 **** systable_beginscan(Relation heapRelation,
{
int i;
! /*
! * Change attribute numbers to be index column numbers.
! *
! * This code could be generalized to search for the index key numbers
! * to substitute, but for now there's no need.
! */
for (i = 0; i < nkeys; i++)
{
! Assert(key[i].sk_attno == irel->rd_index->indkey.values[i]);
! key[i].sk_attno = i + 1;
}
sysscan->iscan = index_beginscan(heapRelation, irel,
--- 194,214 ----
{
int i;
! /* Change attribute numbers to be index column numbers. */
for (i = 0; i < nkeys; i++)
{
! int j;
!
! for (j = 0; j < irel->rd_index->indnatts; j++)
! {
! if (key[i].sk_attno == irel->rd_index->indkey.values[j])
! {
! key[i].sk_attno = j + 1;
! break;
! }
! }
! if (j == irel->rd_index->indnatts)
! elog(ERROR, "column is not in index");
}
sysscan->iscan = index_beginscan(heapRelation, irel,
***************
*** 352,367 **** systable_beginscan_ordered(Relation heapRelation,
sysscan->heap_rel = heapRelation;
sysscan->irel = indexRelation;
! /*
! * Change attribute numbers to be index column numbers.
! *
! * This code could be generalized to search for the index key numbers
! * to substitute, but for now there's no need.
! */
for (i = 0; i < nkeys; i++)
{
! Assert(key[i].sk_attno == indexRelation->rd_index->indkey.values[i]);
! key[i].sk_attno = i + 1;
}
sysscan->iscan = index_beginscan(heapRelation, indexRelation,
--- 357,377 ----
sysscan->heap_rel = heapRelation;
sysscan->irel = indexRelation;
! /* Change attribute numbers to be index column numbers. */
for (i = 0; i < nkeys; i++)
{
! int j;
!
! for (j = 0; j < indexRelation->rd_index->indnatts; j++)
! {
! if (key[i].sk_attno == indexRelation->rd_index->indkey.values[j])
! {
! key[i].sk_attno = j + 1;
! break;
! }
! }
! if (j == indexRelation->rd_index->indnatts)
! elog(ERROR, "column is not in index");
}
sysscan->iscan = index_beginscan(heapRelation, indexRelation,
--
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