From: Anastasia Lubennikova <a.lubennikova@postgrespro.ru>
To: pgsql-hackers@lists.postgresql.org
Subject: Re: CURRENT OF causes an error when IndexOnlyScan is used
Date: Wed, 21 Feb 2018 17:33:55 +0300
Message-ID: <a6ddf99c-6579-e65a-6abd-c0b6259c15c2@postgrespro.ru> (raw)
In-Reply-To: <20180220095252.GA18315@e733.localdomain>
References: <20180201013349.937dfc5f.nagata@sraoss.co.jp>
<20180201014444.f78358df.nagata@sraoss.co.jp>
<22958.1517451171@sss.pgh.pa.us>
<97dc81d3-0ea9-3032-49d9-7983e35fb010@postgrespro.ru>
<20180220095252.GA18315@e733.localdomain>
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
Attachments:return_heaptuple_in_btree_indexonlyscan_v2.patch (text/x-patch, 5.5K) download
commit 391107028d4597e9721a3b274904e49ee69de0cf
Author: Anastasia <a.lubennikova@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.cindex 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.cindex 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.outindex 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.sqlindex 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;
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To: pgsql-hackers@postgresql.org
Cc: a.lubennikova@postgrespro.ru, pgsql-hackers@lists.postgresql.org
Subject: Re: CURRENT OF causes an error when IndexOnlyScan is used
In-Reply-To: <a6ddf99c-6579-e65a-6abd-c0b6259c15c2@postgrespro.ru>
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