Add additional information in the vacuum error context.

The additional information added will be an offset number for heap
operations. This information will help us in finding the exact tuple due
to which the error has occurred.

Author: Mahendra Singh Thalor and Amit Kapila
Reviewed-by: Sawada Masahiko, Justin Pryzby and Amit Kapila
Discussion: https://postgr.es/m/CAKYtNApK488TDF4bMbw+1QH8HJf9cxdNDXquhU50TK5iv_FtCQ@mail.gmail.com

Author: Amit Kapila

src/backend/access/heap/pruneheap.c

@@ -188,7 +188,7 @@ heap_page_prune_opt(Relation relation, Buffer buffer)
 			/* OK to prune */
 			(void) heap_page_prune(relation, buffer, vistest,
 								   limited_xmin, limited_ts,
-								   true, &ignore);
+								   true, &ignore, NULL);
 		}
 
 		/* And release buffer lock */
@@ -213,6 +213,9 @@ heap_page_prune_opt(Relation relation, Buffer buffer)
  * send its own new total to pgstats, and we don't want this delta applied
  * on top of that.)
  *
+ * off_loc is the offset location required by the caller to use in error
+ * callback.
+ *
  * Returns the number of tuples deleted from the page and sets
  * latestRemovedXid.
  */
@@ -221,7 +224,8 @@ heap_page_prune(Relation relation, Buffer buffer,
 				GlobalVisState *vistest,
 				TransactionId old_snap_xmin,
 				TimestampTz old_snap_ts,
-				bool report_stats, TransactionId *latestRemovedXid)
+				bool report_stats, TransactionId *latestRemovedXid,
+				OffsetNumber *off_loc)
 {
 	int			ndeleted = 0;
 	Page		page = BufferGetPage(buffer);
@@ -262,6 +266,13 @@ heap_page_prune(Relation relation, Buffer buffer,
 		if (prstate.marked[offnum])
 			continue;
 
+		/*
+		 * Set the offset number so that we can display it along with any
+		 * error that occurred while processing this tuple.
+		 */
+		if (off_loc)
+			*off_loc = offnum;
+
 		/* Nothing to do if slot is empty or already dead */
 		itemid = PageGetItemId(page, offnum);
 		if (!ItemIdIsUsed(itemid) || ItemIdIsDead(itemid))
@@ -271,6 +282,10 @@ heap_page_prune(Relation relation, Buffer buffer,
 		ndeleted += heap_prune_chain(buffer, offnum, &prstate);
 	}
 
+	/* Clear the offset information once we have processed the given page. */
+	if (off_loc)
+		*off_loc = InvalidOffsetNumber;
+
 	/* Any error while applying the changes is critical */
 	START_CRIT_SECTION();
 

src/backend/access/heap/vacuumlazy.c

@@ -316,13 +316,15 @@ typedef struct LVRelStats
 	/* Used for error callback */
 	char	   *indname;
 	BlockNumber blkno;			/* used only for heap operations */
+	OffsetNumber offnum;		/* used only for heap operations */
 	VacErrPhase phase;
 } LVRelStats;
 
 /* Struct for saving and restoring vacuum error information. */
 typedef struct LVSavedErrInfo
 {
 	BlockNumber blkno;
+	OffsetNumber offnum;
 	VacErrPhase phase;
 } LVSavedErrInfo;
 
@@ -341,7 +343,8 @@ static void lazy_scan_heap(Relation onerel, VacuumParams *params,
 						   LVRelStats *vacrelstats, Relation *Irel, int nindexes,
 						   bool aggressive);
 static void lazy_vacuum_heap(Relation onerel, LVRelStats *vacrelstats);
-static bool lazy_check_needs_freeze(Buffer buf, bool *hastup);
+static bool lazy_check_needs_freeze(Buffer buf, bool *hastup,
+									LVRelStats *vacrelstats);
 static void lazy_vacuum_all_indexes(Relation onerel, Relation *Irel,
 									IndexBulkDeleteResult **stats,
 									LVRelStats *vacrelstats, LVParallelState *lps,
@@ -364,6 +367,7 @@ static void lazy_record_dead_tuple(LVDeadTuples *dead_tuples,
 static bool lazy_tid_reaped(ItemPointer itemptr, void *state);
 static int	vac_cmp_itemptr(const void *left, const void *right);
 static bool heap_page_is_all_visible(Relation rel, Buffer buf,
+									 LVRelStats *vacrelstats,
 									 TransactionId *visibility_cutoff_xid, bool *all_frozen);
 static void lazy_parallel_vacuum_indexes(Relation *Irel, IndexBulkDeleteResult **stats,
 										 LVRelStats *vacrelstats, LVParallelState *lps,
@@ -396,7 +400,8 @@ static LVSharedIndStats *get_indstats(LVShared *lvshared, int n);
 static bool skip_parallel_vacuum_index(Relation indrel, LVShared *lvshared);
 static void vacuum_error_callback(void *arg);
 static void update_vacuum_error_info(LVRelStats *errinfo, LVSavedErrInfo *saved_err_info,
-									 int phase, BlockNumber blkno);
+									 int phase, BlockNumber blkno,
+									 OffsetNumber offnum);
 static void restore_vacuum_error_info(LVRelStats *errinfo, const LVSavedErrInfo *saved_err_info);
 
 
@@ -547,7 +552,8 @@ heap_vacuum_rel(Relation onerel, VacuumParams *params,
 		 * revert to the previous phase.
 		 */
 		update_vacuum_error_info(vacrelstats, NULL, VACUUM_ERRCB_PHASE_TRUNCATE,
-								 vacrelstats->nonempty_pages);
+								 vacrelstats->nonempty_pages,
+								 InvalidOffsetNumber);
 		lazy_truncate_heap(onerel, vacrelstats);
 	}
 
@@ -960,7 +966,7 @@ lazy_scan_heap(Relation onerel, VacuumParams *params, LVRelStats *vacrelstats,
 		pgstat_progress_update_param(PROGRESS_VACUUM_HEAP_BLKS_SCANNED, blkno);
 
 		update_vacuum_error_info(vacrelstats, NULL, VACUUM_ERRCB_PHASE_SCAN_HEAP,
-								 blkno);
+								 blkno, InvalidOffsetNumber);
 
 		if (blkno == next_unskippable_block)
 		{
@@ -1129,7 +1135,7 @@ lazy_scan_heap(Relation onerel, VacuumParams *params, LVRelStats *vacrelstats,
 			 * to use lazy_check_needs_freeze() for both situations, though.
 			 */
 			LockBuffer(buf, BUFFER_LOCK_SHARE);
-			if (!lazy_check_needs_freeze(buf, &hastup))
+			if (!lazy_check_needs_freeze(buf, &hastup, vacrelstats))
 			{
 				UnlockReleaseBuffer(buf);
 				vacrelstats->scanned_pages++;
@@ -1244,7 +1250,8 @@ lazy_scan_heap(Relation onerel, VacuumParams *params, LVRelStats *vacrelstats,
 		 */
 		tups_vacuumed += heap_page_prune(onerel, buf, vistest, false,
 										 InvalidTransactionId, 0,
-										 &vacrelstats->latestRemovedXid);
+										 &vacrelstats->latestRemovedXid,
+										 &vacrelstats->offnum);
 
 		/*
 		 * Now scan the page to collect vacuumable items and check for tuples
@@ -1267,6 +1274,11 @@ lazy_scan_heap(Relation onerel, VacuumParams *params, LVRelStats *vacrelstats,
 		{
 			ItemId		itemid;
 
+			/*
+			 * Set the offset number so that we can display it along with any
+			 * error that occurred while processing this tuple.
+			 */
+			vacrelstats->offnum = offnum;
 			itemid = PageGetItemId(page, offnum);
 
 			/* Unused items require no processing, but we count 'em */
@@ -1468,6 +1480,12 @@ lazy_scan_heap(Relation onerel, VacuumParams *params, LVRelStats *vacrelstats,
 			}
 		}						/* scan along page */
 
+		/*
+		 * Clear the offset information once we have processed all the tuples
+		 * on the page.
+		 */
+		vacrelstats->offnum = InvalidOffsetNumber;
+
 		/*
 		 * If we froze any tuples, mark the buffer dirty, and write a WAL
 		 * record recording the changes.  We must log the changes to be
@@ -1845,7 +1863,7 @@ lazy_vacuum_heap(Relation onerel, LVRelStats *vacrelstats)
 
 	/* Update error traceback information */
 	update_vacuum_error_info(vacrelstats, &saved_err_info, VACUUM_ERRCB_PHASE_VACUUM_HEAP,
-							 InvalidBlockNumber);
+							 InvalidBlockNumber, InvalidOffsetNumber);
 
 	pg_rusage_init(&ru0);
 	npages = 0;
@@ -1927,7 +1945,7 @@ lazy_vacuum_page(Relation onerel, BlockNumber blkno, Buffer buffer,
 
 	/* Update error traceback information */
 	update_vacuum_error_info(vacrelstats, &saved_err_info, VACUUM_ERRCB_PHASE_VACUUM_HEAP,
-							 blkno);
+							 blkno, InvalidOffsetNumber);
 
 	START_CRIT_SECTION();
 
@@ -1979,7 +1997,8 @@ lazy_vacuum_page(Relation onerel, BlockNumber blkno, Buffer buffer,
 	 * dirty, exclusively locked, and, if needed, a full page image has been
 	 * emitted in the log_heap_clean() above.
 	 */
-	if (heap_page_is_all_visible(onerel, buffer, &visibility_cutoff_xid,
+	if (heap_page_is_all_visible(onerel, buffer, vacrelstats,
+								 &visibility_cutoff_xid,
 								 &all_frozen))
 		PageSetAllVisible(page);
 
@@ -2018,7 +2037,7 @@ lazy_vacuum_page(Relation onerel, BlockNumber blkno, Buffer buffer,
  * Also returns a flag indicating whether page contains any tuples at all.
  */
 static bool
-lazy_check_needs_freeze(Buffer buf, bool *hastup)
+lazy_check_needs_freeze(Buffer buf, bool *hastup, LVRelStats *vacrelstats)
 {
 	Page		page = BufferGetPage(buf);
 	OffsetNumber offnum,
@@ -2043,6 +2062,11 @@ lazy_check_needs_freeze(Buffer buf, bool *hastup)
 	{
 		ItemId		itemid;
 
+		/*
+		 * Set the offset number so that we can display it along with any
+		 * error that occurred while processing this tuple.
+		 */
+		vacrelstats->offnum = offnum;
 		itemid = PageGetItemId(page, offnum);
 
 		/* this should match hastup test in count_nondeletable_pages() */
@@ -2057,10 +2081,13 @@ lazy_check_needs_freeze(Buffer buf, bool *hastup)
 
 		if (heap_tuple_needs_freeze(tupleheader, FreezeLimit,
 									MultiXactCutoff, buf))
-			return true;
+			break;
 	}							/* scan along page */
 
-	return false;
+	/* Clear the offset information once we have processed the given page. */
+	vacrelstats->offnum = InvalidOffsetNumber;
+
+	return (offnum <= maxoff);
 }
 
 /*
@@ -2438,7 +2465,7 @@ lazy_vacuum_index(Relation indrel, IndexBulkDeleteResult **stats,
 	vacrelstats->indname = pstrdup(RelationGetRelationName(indrel));
 	update_vacuum_error_info(vacrelstats, &saved_err_info,
 							 VACUUM_ERRCB_PHASE_VACUUM_INDEX,
-							 InvalidBlockNumber);
+							 InvalidBlockNumber, InvalidOffsetNumber);
 
 	/* Do bulk deletion */
 	*stats = index_bulk_delete(&ivinfo, *stats,
@@ -2498,7 +2525,7 @@ lazy_cleanup_index(Relation indrel,
 	vacrelstats->indname = pstrdup(RelationGetRelationName(indrel));
 	update_vacuum_error_info(vacrelstats, &saved_err_info,
 							 VACUUM_ERRCB_PHASE_INDEX_CLEANUP,
-							 InvalidBlockNumber);
+							 InvalidBlockNumber, InvalidOffsetNumber);
 
 	*stats = index_vacuum_cleanup(&ivinfo, *stats);
 
@@ -2522,7 +2549,7 @@ lazy_cleanup_index(Relation indrel,
 						   pg_rusage_show(&ru0))));
 	}
 
-	/* Revert back to the old phase information for error traceback */
+	/* Revert to the previous phase information for error traceback */
 	restore_vacuum_error_info(vacrelstats, &saved_err_info);
 	pfree(vacrelstats->indname);
 	vacrelstats->indname = NULL;
@@ -2964,6 +2991,7 @@ vac_cmp_itemptr(const void *left, const void *right)
  */
 static bool
 heap_page_is_all_visible(Relation rel, Buffer buf,
+						 LVRelStats *vacrelstats,
 						 TransactionId *visibility_cutoff_xid,
 						 bool *all_frozen)
 {
@@ -2988,6 +3016,11 @@ heap_page_is_all_visible(Relation rel, Buffer buf,
 		ItemId		itemid;
 		HeapTupleData tuple;
 
+		/*
+		 * Set the offset number so that we can display it along with any
+		 * error that occurred while processing this tuple.
+		 */
+		vacrelstats->offnum = offnum;
 		itemid = PageGetItemId(page, offnum);
 
 		/* Unused or redirect line pointers are of no interest */
@@ -3065,6 +3098,9 @@ heap_page_is_all_visible(Relation rel, Buffer buf,
 		}
 	}							/* scan along page */
 
+	/* Clear the offset information once we have processed the given page. */
+	vacrelstats->offnum = InvalidOffsetNumber;
+
 	return all_visible;
 }
 
@@ -3586,17 +3622,29 @@ vacuum_error_callback(void *arg)
 	{
 		case VACUUM_ERRCB_PHASE_SCAN_HEAP:
 			if (BlockNumberIsValid(errinfo->blkno))
-				errcontext("while scanning block %u of relation \"%s.%s\"",
-						   errinfo->blkno, errinfo->relnamespace, errinfo->relname);
+			{
+				if (OffsetNumberIsValid(errinfo->offnum))
+					errcontext("while scanning block %u and offset %u of relation \"%s.%s\"",
+							   errinfo->blkno, errinfo->offnum, errinfo->relnamespace, errinfo->relname);
+				else
+					errcontext("while scanning block %u of relation \"%s.%s\"",
+							   errinfo->blkno, errinfo->relnamespace, errinfo->relname);
+			}
 			else
 				errcontext("while scanning relation \"%s.%s\"",
 						   errinfo->relnamespace, errinfo->relname);
 			break;
 
 		case VACUUM_ERRCB_PHASE_VACUUM_HEAP:
 			if (BlockNumberIsValid(errinfo->blkno))
-				errcontext("while vacuuming block %u of relation \"%s.%s\"",
-						   errinfo->blkno, errinfo->relnamespace, errinfo->relname);
+			{
+				if (OffsetNumberIsValid(errinfo->offnum))
+					errcontext("while vacuuming block %u and offset %u of relation \"%s.%s\"",
+							   errinfo->blkno, errinfo->offnum, errinfo->relnamespace, errinfo->relname);
+				else
+					errcontext("while vacuuming block %u of relation \"%s.%s\"",
+							   errinfo->blkno, errinfo->relnamespace, errinfo->relname);
+			}
 			else
 				errcontext("while vacuuming relation \"%s.%s\"",
 						   errinfo->relnamespace, errinfo->relname);
@@ -3631,15 +3679,17 @@ vacuum_error_callback(void *arg)
  */
 static void
 update_vacuum_error_info(LVRelStats *errinfo, LVSavedErrInfo *saved_err_info, int phase,
-						 BlockNumber blkno)
+						 BlockNumber blkno, OffsetNumber offnum)
 {
 	if (saved_err_info)
 	{
+		saved_err_info->offnum = errinfo->offnum;
 		saved_err_info->blkno = errinfo->blkno;
 		saved_err_info->phase = errinfo->phase;
 	}
 
 	errinfo->blkno = blkno;
+	errinfo->offnum = offnum;
 	errinfo->phase = phase;
 }
 
@@ -3650,5 +3700,6 @@ static void
 restore_vacuum_error_info(LVRelStats *errinfo, const LVSavedErrInfo *saved_err_info)
 {
 	errinfo->blkno = saved_err_info->blkno;
+	errinfo->offnum = saved_err_info->offnum;
 	errinfo->phase = saved_err_info->phase;
 }

src/include/access/heapam.h

@@ -178,7 +178,8 @@ extern int	heap_page_prune(Relation relation, Buffer buffer,
 							struct GlobalVisState *vistest,
 							TransactionId limited_oldest_xmin,
 							TimestampTz limited_oldest_ts,
-							bool report_stats, TransactionId *latestRemovedXid);
+							bool report_stats, TransactionId *latestRemovedXid,
+							OffsetNumber *off_loc);
 extern void heap_page_prune_execute(Buffer buffer,
 									OffsetNumber *redirected, int nredirected,
 									OffsetNumber *nowdead, int ndead,