20.02.2018 12:52, Aleksander Alekseev:
Hi Anastasia,
I'd like to propose the patch that fixes the issue.
We already have a way to return heaptuple from IndexOnlyScan,
but it was not applied to b-tree for some reason.
Attached patch solves the reported bug.
Moreover, it will come in handy for "index with included attributes" feature
[1],
where we can store long (and even TOASTed) attributes in indextuple.
[1] https://commitfest.postgresql.org/17/1350/
I believe the patch should include a test that tries to reproduce an
issue it tries to fix.
Also maybe this code that repeats 3 times can be moved to a separate
procedure?
Good point. Updated version with test is attached.
--
Anastasia Lubennikova
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
commit 391107028d4597e9721a3b274904e49ee69de0cf
Author: Anastasia <a.lubennik...@postgrespro.ru>
Date: Wed Feb 21 17:25:11 2018 +0300
return_heaptuple_in_btree_indexonlyscan_v2.patch
diff --git a/src/backend/access/nbtree/nbtree.c b/src/backend/access/nbtree/nbtree.c
index 8158508..db8a55c 100644
--- a/src/backend/access/nbtree/nbtree.c
+++ b/src/backend/access/nbtree/nbtree.c
@@ -374,6 +374,8 @@ btbeginscan(Relation rel, int nkeys, int norderbys)
so->currTuples = so->markTuples = NULL;
scan->xs_itupdesc = RelationGetDescr(rel);
+ scan->xs_hitupdesc = NULL;
+ scan->xs_hitup = NULL;
scan->opaque = so;
diff --git a/src/backend/access/nbtree/nbtsearch.c b/src/backend/access/nbtree/nbtsearch.c
index 51dca64..278f43d 100644
--- a/src/backend/access/nbtree/nbtsearch.c
+++ b/src/backend/access/nbtree/nbtsearch.c
@@ -25,6 +25,9 @@
#include "utils/tqual.h"
+static HeapTuple _bt_fetch_tuple(IndexScanDesc scandesc,
+ ItemPointerData heapTid);
+static void _bt_fill_hitupdesc(IndexScanDesc scan);
static bool _bt_readpage(IndexScanDesc scan, ScanDirection dir,
OffsetNumber offnum);
static void _bt_saveitem(BTScanOpaque so, int itemIndex,
@@ -38,7 +41,52 @@ static bool _bt_endpoint(IndexScanDesc scan, ScanDirection dir);
static void _bt_drop_lock_and_maybe_pin(IndexScanDesc scan, BTScanPos sp);
static inline void _bt_initialize_more_data(BTScanOpaque so, ScanDirection dir);
+/*
+ * Fetch all keys in tuple.
+ * Returns a new HeapTuple containing the originally-indexed data.
+ */
+static HeapTuple
+_bt_fetch_tuple(IndexScanDesc scandesc, ItemPointerData heapTid)
+{
+ Relation index = scandesc->indexRelation;
+ Datum fetchatt[INDEX_MAX_KEYS];
+ bool isnull[INDEX_MAX_KEYS];
+ int i;
+ HeapTuple htuple;
+
+ for (i = 0; i < index->rd_att->natts; i++)
+ {
+ fetchatt[i] = index_getattr(scandesc->xs_itup, i + 1,
+ scandesc->xs_itupdesc, &isnull[i]);
+ }
+
+ htuple = heap_form_tuple(scandesc->xs_hitupdesc, fetchatt, isnull);
+ htuple->t_tableOid = scandesc->heapRelation->rd_id;
+ htuple->t_self = heapTid;
+
+ return htuple;
+}
+
+static void
+_bt_fill_hitupdesc(IndexScanDesc scan)
+{
+ int natts = RelationGetNumberOfAttributes(scan->indexRelation);
+ int attno;
+ /*
+ * The storage type of the index can be different from the original
+ * datatype being indexed, so we cannot just grab the index's tuple
+ * descriptor. Instead, construct a descriptor with the original data
+ * types.
+ */
+ scan->xs_hitupdesc = CreateTemplateTupleDesc(natts, false);
+ for (attno = 1; attno <= natts; attno++)
+ {
+ TupleDescInitEntry(scan->xs_hitupdesc, attno, NULL,
+ scan->indexRelation->rd_opcintype[attno - 1],
+ -1, 0);
+ }
+}
/*
* _bt_drop_lock_and_maybe_pin()
*
@@ -1105,9 +1153,19 @@ readcomplete:
/* OK, itemIndex says what to return */
currItem = &so->currPos.items[so->currPos.itemIndex];
scan->xs_ctup.t_self = currItem->heapTid;
+
if (scan->xs_want_itup)
+ {
scan->xs_itup = (IndexTuple) (so->currTuples + currItem->tupleOffset);
+ if (!scan->xs_hitupdesc)
+ _bt_fill_hitupdesc(scan);
+
+ if (scan->xs_hitup)
+ pfree(scan->xs_hitup);
+ scan->xs_hitup = _bt_fetch_tuple(scan, currItem->heapTid);
+ }
+
return true;
}
@@ -1155,9 +1213,19 @@ _bt_next(IndexScanDesc scan, ScanDirection dir)
/* OK, itemIndex says what to return */
currItem = &so->currPos.items[so->currPos.itemIndex];
scan->xs_ctup.t_self = currItem->heapTid;
+
if (scan->xs_want_itup)
+ {
scan->xs_itup = (IndexTuple) (so->currTuples + currItem->tupleOffset);
+ if (!scan->xs_hitupdesc)
+ _bt_fill_hitupdesc(scan);
+
+ if (scan->xs_hitup)
+ pfree(scan->xs_hitup);
+ scan->xs_hitup = _bt_fetch_tuple(scan, currItem->heapTid);
+ }
+
return true;
}
@@ -1932,9 +2000,19 @@ _bt_endpoint(IndexScanDesc scan, ScanDirection dir)
/* OK, itemIndex says what to return */
currItem = &so->currPos.items[so->currPos.itemIndex];
scan->xs_ctup.t_self = currItem->heapTid;
+
if (scan->xs_want_itup)
+ {
scan->xs_itup = (IndexTuple) (so->currTuples + currItem->tupleOffset);
+ if (!scan->xs_hitupdesc)
+ _bt_fill_hitupdesc(scan);
+
+ if (scan->xs_hitup)
+ pfree(scan->xs_hitup);
+ scan->xs_hitup = _bt_fetch_tuple(scan, currItem->heapTid);
+ }
+
return true;
}
diff --git a/src/test/regress/expected/portals.out b/src/test/regress/expected/portals.out
index 1b8f7b6..d01db92 100644
--- a/src/test/regress/expected/portals.out
+++ b/src/test/regress/expected/portals.out
@@ -1352,3 +1352,25 @@ fetch backward all in c2;
(3 rows)
rollback;
+create table cursor_tbl (i int);
+insert into cursor_tbl values (1);
+VACUUM cursor_tbl;
+begin;
+set enable_seqscan to off;
+declare c cursor for select * from cursor_tbl where i = 1;
+fetch from c;
+ i
+---
+ 1
+(1 row)
+
+update cursor_tbl set i=i+1 where current of c;
+select * from cursor_tbl;
+ i
+---
+ 2
+(1 row)
+
+set enable_seqscan to on;
+rollback;
+drop table cursor_tbl;
diff --git a/src/test/regress/sql/portals.sql b/src/test/regress/sql/portals.sql
index a1c812e..78fee8c 100644
--- a/src/test/regress/sql/portals.sql
+++ b/src/test/regress/sql/portals.sql
@@ -500,3 +500,16 @@ declare c2 scroll cursor for select generate_series(1,3) as g;
fetch all in c2;
fetch backward all in c2;
rollback;
+
+create table cursor_tbl (i int);
+insert into cursor_tbl values (1);
+VACUUM cursor_tbl;
+begin;
+set enable_seqscan to off;
+declare c cursor for select * from cursor_tbl where i = 1;
+fetch from c;
+update cursor_tbl set i=i+1 where current of c;
+select * from cursor_tbl;
+set enable_seqscan to on;
+rollback;
+drop table cursor_tbl;
