Show more detail in heapam rmgr descriptions.

Add helper functions that output arrays in a standard format, and use
the functions inside heapdesc routines.  This allows tools like
pg_walinspect to show a detailed description of the page offset number
arrays for records like PRUNE and VACUUM (unless there was an FPI).

Also document the conventions that desc routines should follow.  Only
the heapdesc routines follow the conventions for now, so they're just
guidelines for the time being.

Based on a suggestion from Andres Freund.

Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-By: Peter Geoghegan <pg@bowt.ie>
Discussion: https://postgr.es/m/flat/20230109215842.fktuhesvayno6o4g%40awork3.anarazel.de

doc/src/sgml/pgwalinspect.sgml

@@ -71,19 +71,19 @@
       after the <replaceable>in_lsn</replaceable> argument.  For
       example:
 <screen>
-postgres=# SELECT * FROM pg_get_wal_record_info('0/1E826E98');
--[ RECORD 1 ]----+----------------------------------------------------
-start_lsn        | 0/1E826F20
-end_lsn          | 0/1E826F60
-prev_lsn         | 0/1E826C80
+postgres=# SELECT * FROM pg_get_wal_record_info('0/E84F5E8');
+-[ RECORD 1 ]----+--------------------------------------------------
+start_lsn        | 0/E84F5E8
+end_lsn          | 0/E84F620
+prev_lsn         | 0/E84F5A8
 xid              | 0
 resource_manager | Heap2
-record_type      | PRUNE
-record_length    | 58
-main_data_length | 8
+record_type      | VACUUM
+record_length    | 50
+main_data_length | 2
 fpi_length       | 0
-description      | snapshotConflictHorizon 33748 nredirected 0 ndead 2
-block_ref        | blkref #0: rel 1663/5/60221 fork main blk 2
+description      | nunused: 1, unused: [ 22 ]
+block_ref        | blkref #0: rel 1663/16389/20884 fork main blk 126
 </screen>
      </para>
      <para>
@@ -144,7 +144,7 @@ block_ref        |
       references.  Returns one row per block reference per WAL record.
       For example:
 <screen>
-postgres=# SELECT * FROM pg_get_wal_block_info('0/10E9D80', '0/10E9DC0') LIMIT 1;
+postgres=# SELECT * FROM pg_get_wal_block_info('0/10E9D80', '0/10E9DC0');
 -[ RECORD 1 ]-----+-----------------------------------
 start_lsn         | 0/10E9D80
 end_lsn           | 0/10E9DC0

src/backend/access/rmgrdesc/Makefile

@@ -23,6 +23,7 @@ OBJS = \
 	nbtdesc.o \
 	relmapdesc.o \
 	replorigindesc.o \
+	rmgrdesc_utils.o \
 	seqdesc.o \
 	smgrdesc.o \
 	spgdesc.o \

src/backend/access/rmgrdesc/heapdesc.c

@@ -15,20 +15,52 @@
 #include "postgres.h"
 
 #include "access/heapam_xlog.h"
+#include "access/rmgrdesc_utils.h"
 
 static void
 out_infobits(StringInfo buf, uint8 infobits)
 {
+	if ((infobits & XLHL_XMAX_IS_MULTI) == 0 &&
+		(infobits & XLHL_XMAX_LOCK_ONLY) == 0 &&
+		(infobits & XLHL_XMAX_EXCL_LOCK) == 0 &&
+		(infobits & XLHL_XMAX_KEYSHR_LOCK) == 0 &&
+		(infobits & XLHL_KEYS_UPDATED) == 0)
+		return;
+
+	appendStringInfoString(buf, ", infobits: [");
+
 	if (infobits & XLHL_XMAX_IS_MULTI)
-		appendStringInfoString(buf, "IS_MULTI ");
+		appendStringInfoString(buf, " IS_MULTI");
 	if (infobits & XLHL_XMAX_LOCK_ONLY)
-		appendStringInfoString(buf, "LOCK_ONLY ");
+		appendStringInfoString(buf, ", LOCK_ONLY");
 	if (infobits & XLHL_XMAX_EXCL_LOCK)
-		appendStringInfoString(buf, "EXCL_LOCK ");
+		appendStringInfoString(buf, ", EXCL_LOCK");
 	if (infobits & XLHL_XMAX_KEYSHR_LOCK)
-		appendStringInfoString(buf, "KEYSHR_LOCK ");
+		appendStringInfoString(buf, ", KEYSHR_LOCK");
 	if (infobits & XLHL_KEYS_UPDATED)
-		appendStringInfoString(buf, "KEYS_UPDATED ");
+		appendStringInfoString(buf, ", KEYS_UPDATED");
+
+	appendStringInfoString(buf, " ]");
+}
+
+static void
+plan_elem_desc(StringInfo buf, void *plan, void *data)
+{
+	xl_heap_freeze_plan *new_plan = (xl_heap_freeze_plan *) plan;
+	OffsetNumber **offsets = data;
+
+	appendStringInfo(buf, "{ xmax: %u, infomask: %u, infomask2: %u, ntuples: %u",
+					 new_plan->xmax,
+					 new_plan->t_infomask, new_plan->t_infomask2,
+					 new_plan->ntuples);
+
+	appendStringInfoString(buf, ", offsets:");
+	array_desc(buf, *offsets, sizeof(OffsetNumber), new_plan->ntuples,
+			   &offset_elem_desc, NULL);
+
+	*offsets += new_plan->ntuples;
+
+	appendStringInfo(buf, " }");
 }
 
 void
@@ -42,14 +74,15 @@ heap_desc(StringInfo buf, XLogReaderState *record)
 	{
 		xl_heap_insert *xlrec = (xl_heap_insert *) rec;
 
-		appendStringInfo(buf, "off %u flags 0x%02X", xlrec->offnum,
+		appendStringInfo(buf, "off: %u, flags: 0x%02X",
+						 xlrec->offnum,
 						 xlrec->flags);
 	}
 	else if (info == XLOG_HEAP_DELETE)
 	{
 		xl_heap_delete *xlrec = (xl_heap_delete *) rec;
 
-		appendStringInfo(buf, "off %u flags 0x%02X ",
+		appendStringInfo(buf, "off: %u, flags: 0x%02X",
 						 xlrec->offnum,
 						 xlrec->flags);
 		out_infobits(buf, xlrec->infobits_set);
@@ -58,12 +91,12 @@ heap_desc(StringInfo buf, XLogReaderState *record)
 	{
 		xl_heap_update *xlrec = (xl_heap_update *) rec;
 
-		appendStringInfo(buf, "off %u xmax %u flags 0x%02X ",
+		appendStringInfo(buf, "off: %u, xmax: %u, flags: 0x%02X",
 						 xlrec->old_offnum,
 						 xlrec->old_xmax,
 						 xlrec->flags);
 		out_infobits(buf, xlrec->old_infobits_set);
-		appendStringInfo(buf, "; new off %u xmax %u",
+		appendStringInfo(buf, ", new off: %u, xmax %u",
 						 xlrec->new_offnum,
 						 xlrec->new_xmax);
 	}
@@ -71,39 +104,42 @@ heap_desc(StringInfo buf, XLogReaderState *record)
 	{
 		xl_heap_update *xlrec = (xl_heap_update *) rec;
 
-		appendStringInfo(buf, "off %u xmax %u flags 0x%02X ",
+		appendStringInfo(buf, "off: %u, xmax: %u, flags: 0x%02X",
 						 xlrec->old_offnum,
 						 xlrec->old_xmax,
 						 xlrec->flags);
 		out_infobits(buf, xlrec->old_infobits_set);
-		appendStringInfo(buf, "; new off %u xmax %u",
+		appendStringInfo(buf, ", new off: %u, xmax: %u",
 						 xlrec->new_offnum,
 						 xlrec->new_xmax);
 	}
 	else if (info == XLOG_HEAP_TRUNCATE)
 	{
 		xl_heap_truncate *xlrec = (xl_heap_truncate *) rec;
-		int			i;
 
+		appendStringInfoString(buf, "flags: [");
 		if (xlrec->flags & XLH_TRUNCATE_CASCADE)
-			appendStringInfoString(buf, "cascade ");
+			appendStringInfoString(buf, " CASCADE");
 		if (xlrec->flags & XLH_TRUNCATE_RESTART_SEQS)
-			appendStringInfoString(buf, "restart_seqs ");
-		appendStringInfo(buf, "nrelids %u relids", xlrec->nrelids);
-		for (i = 0; i < xlrec->nrelids; i++)
-			appendStringInfo(buf, " %u", xlrec->relids[i]);
+			appendStringInfoString(buf, ", RESTART_SEQS");
+		appendStringInfoString(buf, " ]");
+
+		appendStringInfo(buf, ", nrelids: %u", xlrec->nrelids);
+		appendStringInfoString(buf, ", relids:");
+		array_desc(buf, xlrec->relids, sizeof(Oid), xlrec->nrelids,
+				   &relid_desc, NULL);
 	}
 	else if (info == XLOG_HEAP_CONFIRM)
 	{
 		xl_heap_confirm *xlrec = (xl_heap_confirm *) rec;
 
-		appendStringInfo(buf, "off %u", xlrec->offnum);
+		appendStringInfo(buf, "off: %u", xlrec->offnum);
 	}
 	else if (info == XLOG_HEAP_LOCK)
 	{
 		xl_heap_lock *xlrec = (xl_heap_lock *) rec;
 
-		appendStringInfo(buf, "off %u: xid %u: flags 0x%02X ",
+		appendStringInfo(buf, "off: %u, xid: %u, flags: 0x%02X",
 						 xlrec->offnum, xlrec->locking_xid, xlrec->flags);
 		out_infobits(buf, xlrec->infobits_set);
 	}
@@ -111,9 +147,10 @@ heap_desc(StringInfo buf, XLogReaderState *record)
 	{
 		xl_heap_inplace *xlrec = (xl_heap_inplace *) rec;
 
-		appendStringInfo(buf, "off %u", xlrec->offnum);
+		appendStringInfo(buf, "off: %u", xlrec->offnum);
 	}
 }
+
 void
 heap2_desc(StringInfo buf, XLogReaderState *record)
 {
@@ -125,43 +162,105 @@ heap2_desc(StringInfo buf, XLogReaderState *record)
 	{
 		xl_heap_prune *xlrec = (xl_heap_prune *) rec;
 
-		appendStringInfo(buf, "snapshotConflictHorizon %u nredirected %u ndead %u",
+		appendStringInfo(buf, "snapshotConflictHorizon: %u, nredirected: %u, ndead: %u",
 						 xlrec->snapshotConflictHorizon,
 						 xlrec->nredirected,
 						 xlrec->ndead);
+
+		if (!XLogRecHasBlockImage(record, 0))
+		{
+			OffsetNumber *end;
+			OffsetNumber *redirected;
+			OffsetNumber *nowdead;
+			OffsetNumber *nowunused;
+			int			nredirected;
+			int			nunused;
+			Size		datalen;
+
+			redirected = (OffsetNumber *) XLogRecGetBlockData(record, 0,
+															  &datalen);
+
+			nredirected = xlrec->nredirected;
+			end = (OffsetNumber *) ((char *) redirected + datalen);
+			nowdead = redirected + (nredirected * 2);
+			nowunused = nowdead + xlrec->ndead;
+			nunused = (end - nowunused);
+			Assert(nunused >= 0);
+
+			appendStringInfo(buf, ", nunused: %u", nunused);
+
+			appendStringInfoString(buf, ", redirected:");
+			array_desc(buf, redirected, sizeof(OffsetNumber) * 2,
+					   nredirected, &redirect_elem_desc, NULL);
+			appendStringInfoString(buf, ", dead:");
+			array_desc(buf, nowdead, sizeof(OffsetNumber), xlrec->ndead,
+					   &offset_elem_desc, NULL);
+			appendStringInfoString(buf, ", unused:");
+			array_desc(buf, nowunused, sizeof(OffsetNumber), nunused,
+					   &offset_elem_desc, NULL);
+		}
 	}
 	else if (info == XLOG_HEAP2_VACUUM)
 	{
 		xl_heap_vacuum *xlrec = (xl_heap_vacuum *) rec;
 
-		appendStringInfo(buf, "nunused %u", xlrec->nunused);
+		appendStringInfo(buf, "nunused: %u", xlrec->nunused);
+
+		if (!XLogRecHasBlockImage(record, 0))
+		{
+			OffsetNumber *nowunused;
+
+			nowunused = (OffsetNumber *) XLogRecGetBlockData(record, 0, NULL);
+
+			appendStringInfoString(buf, ", unused:");
+			array_desc(buf, nowunused, sizeof(OffsetNumber), xlrec->nunused,
+					   &offset_elem_desc, NULL);
+		}
 	}
 	else if (info == XLOG_HEAP2_FREEZE_PAGE)
 	{
 		xl_heap_freeze_page *xlrec = (xl_heap_freeze_page *) rec;
 
-		appendStringInfo(buf, "snapshotConflictHorizon %u nplans %u",
+		appendStringInfo(buf, "snapshotConflictHorizon: %u, nplans: %u",
 						 xlrec->snapshotConflictHorizon, xlrec->nplans);
+
+		if (!XLogRecHasBlockImage(record, 0))
+		{
+			xl_heap_freeze_plan *plans;
+			OffsetNumber *offsets;
+
+			plans = (xl_heap_freeze_plan *) XLogRecGetBlockData(record, 0, NULL);
+			offsets = (OffsetNumber *) &plans[xlrec->nplans];
+			appendStringInfoString(buf, ", plans:");
+			array_desc(buf, plans, sizeof(xl_heap_freeze_plan), xlrec->nplans,
+					   &plan_elem_desc, &offsets);
+		}
 	}
 	else if (info == XLOG_HEAP2_VISIBLE)
 	{
 		xl_heap_visible *xlrec = (xl_heap_visible *) rec;
 
-		appendStringInfo(buf, "snapshotConflictHorizon %u flags 0x%02X",
+		appendStringInfo(buf, "snapshotConflictHorizon: %u, flags: 0x%02X",
 						 xlrec->snapshotConflictHorizon, xlrec->flags);
 	}
 	else if (info == XLOG_HEAP2_MULTI_INSERT)
 	{
 		xl_heap_multi_insert *xlrec = (xl_heap_multi_insert *) rec;
+		bool		isinit = (XLogRecGetInfo(record) & XLOG_HEAP_INIT_PAGE) != 0;
 
-		appendStringInfo(buf, "%d tuples flags 0x%02X", xlrec->ntuples,
+		appendStringInfo(buf, "ntuples: %d, flags: 0x%02X", xlrec->ntuples,
 						 xlrec->flags);
+
+		appendStringInfoString(buf, ", offsets:");
+		if (!XLogRecHasBlockImage(record, 0) && !isinit)
+			array_desc(buf, xlrec->offsets, sizeof(OffsetNumber),
+					   xlrec->ntuples, &offset_elem_desc, NULL);
 	}
 	else if (info == XLOG_HEAP2_LOCK_UPDATED)
 	{
 		xl_heap_lock_updated *xlrec = (xl_heap_lock_updated *) rec;
 
-		appendStringInfo(buf, "off %u: xmax %u: flags 0x%02X ",
+		appendStringInfo(buf, "off: %u, xmax: %u, flags: 0x%02X",
 						 xlrec->offnum, xlrec->xmax, xlrec->flags);
 		out_infobits(buf, xlrec->infobits_set);
 	}
@@ -169,13 +268,13 @@ heap2_desc(StringInfo buf, XLogReaderState *record)
 	{
 		xl_heap_new_cid *xlrec = (xl_heap_new_cid *) rec;
 
-		appendStringInfo(buf, "rel %u/%u/%u; tid %u/%u",
+		appendStringInfo(buf, "rel: %u/%u/%u, tid: %u/%u",
 						 xlrec->target_locator.spcOid,
 						 xlrec->target_locator.dbOid,
 						 xlrec->target_locator.relNumber,
 						 ItemPointerGetBlockNumber(&(xlrec->target_tid)),
 						 ItemPointerGetOffsetNumber(&(xlrec->target_tid)));
-		appendStringInfo(buf, "; cmin: %u, cmax: %u, combo: %u",
+		appendStringInfo(buf, ", cmin: %u, cmax: %u, combo: %u",
 						 xlrec->cmin, xlrec->cmax, xlrec->combocid);
 	}
 }

src/backend/access/rmgrdesc/meson.build

@@ -16,6 +16,7 @@ rmgr_desc_sources = files(
   'nbtdesc.c',
   'relmapdesc.c',
   'replorigindesc.c',
+  'rmgrdesc_utils.c',
   'seqdesc.c',
   'smgrdesc.c',
   'spgdesc.c',

src/backend/access/rmgrdesc/rmgrdesc_utils.c

@@ -0,0 +1,84 @@
+/*-------------------------------------------------------------------------
+ *
+ * rmgrdesc_utils.c
+ *	  Support functions for rmgrdesc routines
+ *
+ * Copyright (c) 2023, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/access/rmgrdesc/rmgrdesc_utils.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/rmgrdesc_utils.h"
+#include "storage/off.h"
+
+/*
+ * Guidelines for formatting desc functions:
+ *
+ * member1_name: member1_value, member2_name: member2_value
+ *
+ * If the value is a list, please use:
+ *
+ * member3_name: [ member3_list_value1, member3_list_value2 ]
+ *
+ * The first item appended to the string should not be prepended by any spaces
+ * or comma, however all subsequent appends to the string are responsible for
+ * prepending themselves with a comma followed by a space.
+ *
+ * Arrays should have a space between the opening square bracket and first
+ * element and between the last element and closing brace.
+ *
+ * Flags should be in ALL CAPS.
+ *
+ * For lists/arrays of items, the number of those items should be listed at
+ * the beginning with all of the other numbers.
+ *
+ * List punctuation should still be included even if there are 0 items.
+ *
+ * Composite objects in a list should be surrounded with { }.
+ */
+void
+array_desc(StringInfo buf, void *array, size_t elem_size, int count,
+		   void (*elem_desc) (StringInfo buf, void *elem, void *data),
+		   void *data)
+{
+	if (count == 0)
+	{
+		appendStringInfoString(buf, " []");
+		return;
+	}
+	appendStringInfo(buf, " [");
+	for (int i = 0; i < count; i++)
+	{
+		if (i > 0)
+			appendStringInfoString(buf, ",");
+		appendStringInfoString(buf, " ");
+
+		elem_desc(buf, (char *) array + elem_size * i, data);
+	}
+	appendStringInfoString(buf, " ]");
+}
+
+void
+offset_elem_desc(StringInfo buf, void *offset, void *data)
+{
+	appendStringInfo(buf, "%u", *(OffsetNumber *) offset);
+}
+
+void
+redirect_elem_desc(StringInfo buf, void *offset, void *data)
+{
+	OffsetNumber *new_offset = (OffsetNumber *) offset;
+
+	appendStringInfo(buf, "%u->%u", new_offset[0], new_offset[1]);
+}
+
+void
+relid_desc(StringInfo buf, void *relid, void *data)
+{
+	appendStringInfo(buf, "%u", *(Oid *) relid);
+}

src/bin/pg_waldump/Makefile

@@ -18,7 +18,7 @@ OBJS = \
 
 override CPPFLAGS := -DFRONTEND $(CPPFLAGS)
 
-RMGRDESCSOURCES = $(sort $(notdir $(wildcard $(top_srcdir)/src/backend/access/rmgrdesc/*desc.c)))
+RMGRDESCSOURCES = $(sort $(notdir $(wildcard $(top_srcdir)/src/backend/access/rmgrdesc/*desc*.c)))
 RMGRDESCOBJS = $(patsubst %.c,%.o,$(RMGRDESCSOURCES))
 
 

src/include/access/rmgrdesc_utils.h

@@ -0,0 +1,22 @@
+/*-------------------------------------------------------------------------
+ *
+ * rmgrdesc_utils.h
+ *	  Support functions for rmgrdesc routines
+ *
+ * Copyright (c) 2023, PostgreSQL Global Development Group
+ *
+ * src/include/access/rmgrdesc_utils.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef RMGRDESC_UTILS_H_
+#define RMGRDESC_UTILS_H_
+
+extern void array_desc(StringInfo buf, void *array, size_t elem_size, int count,
+					   void (*elem_desc) (StringInfo buf, void *elem, void *data),
+					   void *data);
+extern void offset_elem_desc(StringInfo buf, void *offset, void *data);
+extern void redirect_elem_desc(StringInfo buf, void *offset, void *data);
+extern void relid_desc(StringInfo buf, void *relid, void *data);
+
+#endif							/* RMGRDESC_UTILS_H */