Fix PlanRowMark/ExecRowMark structures to handle inheritance correctly.

In an inherited UPDATE/DELETE, each target table has its own subplan,
because it might have a column set different from other targets.  This
means that the resjunk columns we add to support EvalPlanQual might be
at different physical column numbers in each subplan.  The EvalPlanQual
rewrite I did for 9.0 failed to account for this, resulting in possible
misbehavior or even crashes during concurrent updates to the same row,
as seen in a recent report from Gordon Shannon.  Revise the data structure
so that we track resjunk column numbers separately for each subplan.

I also chose to move responsibility for identifying the physical column
numbers back to executor startup, instead of assuming that numbers derived
during preprocess_targetlist would stay valid throughout subsequent
massaging of the plan.  That's a bit slower, so we might want to consider
undoing it someday; but it would complicate the patch considerably and
didn't seem justifiable in a bug fix that has to be back-patched to 9.0.

1 files changed, 15 insertions, 6 deletions

diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 1a67e0ff84a..011c6869f27 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -158,6 +158,9 @@ typedef struct Result
  *	 ModifyTable node -
  *		Apply rows produced by subplan(s) to result table(s),
  *		by inserting, updating, or deleting.
+ *
+ * Note that rowMarks and epqParam are presumed to be valid for all the
+ * subplan(s); they can't contain any info that varies across subplans.
  * ----------------
  */
 typedef struct ModifyTable
@@ -734,9 +737,18 @@ typedef enum RowMarkType
  * prti == parent's RT index, and can therefore be recognized as children by
  * the fact that prti != rti.
  *
- * The AttrNumbers are filled in during preprocess_targetlist.	We use
- * different subsets of them for plain relations, inheritance children,
- * and non-table relations.
+ * The planner also adds resjunk output columns to the plan that carry
+ * information sufficient to identify the locked or fetched rows.  For
+ * tables (markType != ROW_MARK_COPY), these columns are named
+ *		tableoid%u			OID of table
+ *		ctid%u				TID of row
+ * The tableoid column is only present for an inheritance hierarchy.
+ * When markType == ROW_MARK_COPY, there is instead a single column named
+ *		wholerow%u			whole-row value of relation
+ * In all three cases, %u represents the parent rangetable index (prti).
+ * Note this means that all tables in an inheritance hierarchy share the
+ * same resjunk column names.  However, in an inherited UPDATE/DELETE the
+ * columns could have different physical column numbers in each subplan.
  */
 typedef struct PlanRowMark
 {
@@ -746,9 +758,6 @@ typedef struct PlanRowMark
 	RowMarkType markType;		/* see enum above */
 	bool		noWait;			/* NOWAIT option */
 	bool		isParent;		/* true if this is a "dummy" parent entry */
-	AttrNumber	ctidAttNo;		/* resno of ctid junk attribute, if any */
-	AttrNumber	toidAttNo;		/* resno of tableoid junk attribute, if any */
-	AttrNumber	wholeAttNo;		/* resno of whole-row junk attribute, if any */
 } PlanRowMark;