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[BUGS] backend crash with certain statements/tables
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#1
 
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[BUGS] backend crash with certain statements/tables -
03-02-2004
, 10:34 AM
#2
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Running any of these statements on my database causes the backend to crash (example from PG log below): |
that tries to avoid "unnecessary" projection steps. In the "SELECT *
FROM foo LIMIT" case, the scan plan decides it need not do projection,
but actually one must occur (else heap_insert will scribble on the
source table :-(). The junkfilter code in execMain.c is supposed to
catch this situation, but it's fooled by the presence of a LIMIT step.
There may be some related cases, need to think more.
I should have a patch later today.
regards, tom lane
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#3
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I should have a patch later today. |
Thanks,
- Jeff
--
Jeff Bohmer
VisionLink, Inc.
_________________________________
303.402.0170
www.visionlink.org
_________________________________
People. Tools. Change. Community.
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#4
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Great! I'd like to try out the patch when it's ready. |
regards, tom lane
Index: src/backend/executor/execAmi.c
================================================== =================
RCS file: /cvsroot/pgsql-server/src/backend/executor/execAmi.c,v
retrieving revision 1.75.4.1
diff -c -r1.75.4.1 execAmi.c
*** src/backend/executor/execAmi.c 18 Dec 2003 20:21:53 -0000 1.75.4.1
--- src/backend/executor/execAmi.c 2 Mar 2004 18:52:18 -0000
***************
*** 348,350 ****
--- 348,415 ----
return false;
}
}
+
+ /*
+ * ExecMayReturnRawTuples
+ * Check whether a plan tree may return "raw" disk tuples (that is,
+ * pointers to original data in disk buffers, as opposed to temporary
+ * tuples constructed by projection steps). In the case of Append,
+ * some subplans may return raw tuples and others projected tuples;
+ * we return "true" if any of the returned tuples could be raw.
+ *
+ * This must be passed an already-initialized planstate tree, because we
+ * need to look at the results of ExecAssignScanProjectionInfo().
+ */
+ bool
+ ExecMayReturnRawTuples(PlanState *node)
+ {
+ /*
+ * At a table scan node, we check whether ExecAssignScanProjectionInfo
+ * decided to do projection or not. Most non-scan nodes always project
+ * and so we can return "false" immediately. For nodes that don't
+ * project but just pass up input tuples, we have to recursively
+ * examine the input plan node.
+ *
+ * Note: Hash and Material are listed here because they sometimes
+ * return an original input tuple, not a copy. But Sort and SetOp
+ * never return an original tuple, so they can be treated like
+ * projecting nodes.
+ */
+ switch (nodeTag(node))
+ {
+ /* Table scan nodes */
+ case T_SeqScanState:
+ case T_IndexScanState:
+ case T_TidScanState:
+ case T_SubqueryScanState:
+ case T_FunctionScanState:
+ if (node->ps_ProjInfo == NULL)
+ return true;
+ break;
+
+ /* Non-projecting nodes */
+ case T_HashState:
+ case T_MaterialState:
+ case T_UniqueState:
+ case T_LimitState:
+ return ExecMayReturnRawTuples(node->lefttree);
+
+ case T_AppendState:
+ {
+ AppendState *appendstate = (AppendState *) node;
+ int j;
+
+ for (j = 0; j < appendstate->as_nplans; j++)
+ {
+ if (ExecMayReturnRawTuples(appendstate->appendplans[j]))
+ return true;
+ }
+ break;
+ }
+
+ /* All projecting node types come here */
+ default:
+ break;
+ }
+ return false;
+ }
Index: src/backend/executor/execMain.c
================================================== =================
RCS file: /cvsroot/pgsql-server/src/backend/executor/execMain.c,v
retrieving revision 1.220.2.1
diff -c -r1.220.2.1 execMain.c
*** src/backend/executor/execMain.c 22 Jan 2004 02:23:35 -0000 1.220.2.1
--- src/backend/executor/execMain.c 2 Mar 2004 18:52:18 -0000
***************
*** 665,674 ****
/*
* Initialize the junk filter if needed. SELECT and INSERT queries
* need a filter if there are any junk attrs in the tlist. INSERT and
! * SELECT INTO also need a filter if the top plan node is a scan node
! * that's not doing projection (else we'll be scribbling on the scan
! * tuple!) UPDATE and DELETE always need a filter, since there's
! * always a junk 'ctid' attribute present --- no need to look first.
*/
{
bool junk_filter_needed = false;
--- 665,674 ----
/*
* Initialize the junk filter if needed. SELECT and INSERT queries
* need a filter if there are any junk attrs in the tlist. INSERT and
! * SELECT INTO also need a filter if the plan may return raw disk tuples
! * (else heap_insert will be scribbling on the source relation!).
! * UPDATE and DELETE always need a filter, since there's always a junk
! * 'ctid' attribute present --- no need to look first.
*/
{
bool junk_filter_needed = false;
***************
*** 689,706 ****
}
}
if (!junk_filter_needed &&
! (operation == CMD_INSERT || do_select_into))
! {
! if (IsA(planstate, SeqScanState) ||
! IsA(planstate, IndexScanState) ||
! IsA(planstate, TidScanState) ||
! IsA(planstate, SubqueryScanState) ||
! IsA(planstate, FunctionScanState))
! {
! if (planstate->ps_ProjInfo == NULL)
! junk_filter_needed = true;
! }
! }
break;
case CMD_UPDATE:
case CMD_DELETE:
--- 689,697 ----
}
}
if (!junk_filter_needed &&
! (operation == CMD_INSERT || do_select_into) &&
! ExecMayReturnRawTuples(planstate))
! junk_filter_needed = true;
break;
case CMD_UPDATE:
case CMD_DELETE:
Index: src/include/executor/executor.h
================================================== =================
RCS file: /cvsroot/pgsql-server/src/include/executor/executor.h,v
retrieving revision 1.102.2.2
diff -c -r1.102.2.2 executor.h
*** src/include/executor/executor.h 22 Jan 2004 02:23:35 -0000 1.102.2.2
--- src/include/executor/executor.h 2 Mar 2004 18:52:19 -0000
***************
*** 36,41 ****
--- 36,42 ----
extern void ExecRestrPos(PlanState *node);
extern bool ExecSupportsMarkRestore(NodeTag plantype);
extern bool ExecSupportsBackwardScan(Plan *node);
+ extern bool ExecMayReturnRawTuples(PlanState *node);
/*
* prototypes from functions in execGrouping.c
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#5
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Jeff Bohmer <bohmer (AT) visionlink (DOT) org> writes: Great! I'd like to try out the patch when it's ready. Here ya go. |
Works for me on OS X and Linux.
Thank you very much!
- Jeff
--
Jeff Bohmer
VisionLink, Inc.
_________________________________
303.402.0170
www.visionlink.org
_________________________________
People. Tools. Change. Community.
---------------------------(end of broadcast)---------------------------
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