Teach pageinspect about nbtree deduplication.

Add a new bt_metap() column to display the metapage's allequalimage
field.  Also add three new columns to contrib/pageinspect's
bt_page_items() function:

* Add a boolean column ("dead") that displays the LP_DEAD bit value for
each non-pivot tuple.

* Add a TID column ("htid") that displays a single heap TID value for
each tuple.  This is the TID that is returned by BTreeTupleGetHeapTID(),
so comparable values are shown for pivot tuples, plain non-pivot tuples,
and posting list tuples.

* Add a TID array column ("tids") that displays TIDs from each tuple's
posting list, if any.  This works just like the "tids" column from
pageinspect's gin_leafpage_items() function.

No version bump for the pageinspect extension, since there hasn't been a
stable Postgres release since the last version bump (the last bump was
part of commit 58b4cb30).

Author: Peter Geoghegan
Discussion: https://postgr.es/m/CAH2-WzmSMmU2eNvY9+a4MNP+z02h6sa-uxZvN3un6jY02ZVBSw@mail.gmail.com

contrib/pageinspect/btreefuncs.c

@@ -31,9 +31,11 @@
 #include "access/relation.h"
 #include "catalog/namespace.h"
 #include "catalog/pg_am.h"
+#include "catalog/pg_type.h"
 #include "funcapi.h"
 #include "miscadmin.h"
 #include "pageinspect.h"
+#include "utils/array.h"
 #include "utils/builtins.h"
 #include "utils/rel.h"
 #include "utils/varlena.h"
@@ -45,6 +47,8 @@ PG_FUNCTION_INFO_V1(bt_page_stats);
 
 #define IS_INDEX(r) ((r)->rd_rel->relkind == RELKIND_INDEX)
 #define IS_BTREE(r) ((r)->rd_rel->relam == BTREE_AM_OID)
+#define DatumGetItemPointer(X)	 ((ItemPointer) DatumGetPointer(X))
+#define ItemPointerGetDatum(X)	 PointerGetDatum(X)
 
 /* note: BlockNumber is unsigned, hence can't be negative */
 #define CHECK_RELATION_BLOCK_RANGE(rel, blkno) { \
@@ -243,6 +247,9 @@ struct user_args
 {
 	Page		page;
 	OffsetNumber offset;
+	bool		leafpage;
+	bool		rightmost;
+	TupleDesc	tupd;
 };
 
 /*-------------------------------------------------------
@@ -252,17 +259,25 @@ struct user_args
  * ------------------------------------------------------
  */
 static Datum
-bt_page_print_tuples(FuncCallContext *fctx, Page page, OffsetNumber offset)
+bt_page_print_tuples(FuncCallContext *fctx, struct user_args *uargs)
 {
-	char	   *values[6];
+	Page		page = uargs->page;
+	OffsetNumber offset = uargs->offset;
+	bool		leafpage = uargs->leafpage;
+	bool		rightmost = uargs->rightmost;
+	bool		ispivottuple;
+	Datum		values[9];
+	bool		nulls[9];
 	HeapTuple	tuple;
 	ItemId		id;
 	IndexTuple	itup;
 	int			j;
 	int			off;
 	int			dlen;
-	char	   *dump;
+	char	   *dump,
+			   *datacstring;
 	char	   *ptr;
+	ItemPointer htid;
 
 	id = PageGetItemId(page, offset);
 
@@ -272,18 +287,49 @@ bt_page_print_tuples(FuncCallContext *fctx, Page page, OffsetNumber offset)
 	itup = (IndexTuple) PageGetItem(page, id);
 
 	j = 0;
-	values[j++] = psprintf("%d", offset);
-	values[j++] = psprintf("(%u,%u)",
-						   ItemPointerGetBlockNumberNoCheck(&itup->t_tid),
-						   ItemPointerGetOffsetNumberNoCheck(&itup->t_tid));
-	values[j++] = psprintf("%d", (int) IndexTupleSize(itup));
-	values[j++] = psprintf("%c", IndexTupleHasNulls(itup) ? 't' : 'f');
-	values[j++] = psprintf("%c", IndexTupleHasVarwidths(itup) ? 't' : 'f');
+	memset(nulls, 0, sizeof(nulls));
+	values[j++] = DatumGetInt16(offset);
+	values[j++] = ItemPointerGetDatum(&itup->t_tid);
+	values[j++] = Int32GetDatum((int) IndexTupleSize(itup));
+	values[j++] = BoolGetDatum(IndexTupleHasNulls(itup));
+	values[j++] = BoolGetDatum(IndexTupleHasVarwidths(itup));
 
 	ptr = (char *) itup + IndexInfoFindDataOffset(itup->t_info);
 	dlen = IndexTupleSize(itup) - IndexInfoFindDataOffset(itup->t_info);
+
+	/*
+	 * Make sure that "data" column does not include posting list or pivot
+	 * tuple representation of heap TID(s).
+	 *
+	 * Note: BTreeTupleIsPivot() won't work reliably on !heapkeyspace indexes
+	 * (those built before BTREE_VERSION 4), but we have no way of determining
+	 * if this page came from a !heapkeyspace index.  We may only have a bytea
+	 * nbtree page image to go on, so in general there is no metapage that we
+	 * can check.
+	 *
+	 * That's okay here because BTreeTupleIsPivot() can only return false for
+	 * a !heapkeyspace pivot, never true for a !heapkeyspace non-pivot.  Since
+	 * heap TID isn't part of the keyspace in a !heapkeyspace index anyway,
+	 * there cannot possibly be a pivot tuple heap TID representation that we
+	 * fail to make an adjustment for.  A !heapkeyspace index can have
+	 * BTreeTupleIsPivot() return true (due to things like suffix truncation
+	 * for INCLUDE indexes in Postgres v11), but when that happens
+	 * BTreeTupleGetHeapTID() can be trusted to work reliably (i.e. return
+	 * NULL).
+	 *
+	 * Note: BTreeTupleIsPosting() always works reliably, even with
+	 * !heapkeyspace indexes.
+	 */
+	if (BTreeTupleIsPosting(itup))
+		dlen -= IndexTupleSize(itup) - BTreeTupleGetPostingOffset(itup);
+	else if (BTreeTupleIsPivot(itup) && BTreeTupleGetHeapTID(itup) != NULL)
+		dlen -= MAXALIGN(sizeof(ItemPointerData));
+
+	if (dlen < 0 || dlen > INDEX_SIZE_MASK)
+		elog(ERROR, "invalid tuple length %d for tuple at offset number %u",
+			 dlen, offset);
 	dump = palloc0(dlen * 3 + 1);
-	values[j] = dump;
+	datacstring = dump;
 	for (off = 0; off < dlen; off++)
 	{
 		if (off > 0)
@@ -291,8 +337,62 @@ bt_page_print_tuples(FuncCallContext *fctx, Page page, OffsetNumber offset)
 		sprintf(dump, "%02x", *(ptr + off) & 0xff);
 		dump += 2;
 	}
+	values[j++] = CStringGetTextDatum(datacstring);
+	pfree(datacstring);
+
+	/*
+	 * We need to work around the BTreeTupleIsPivot() !heapkeyspace limitation
+	 * again.  Deduce whether or not tuple must be a pivot tuple based on
+	 * whether or not the page is a leaf page, as well as the page offset
+	 * number of the tuple.
+	 */
+	ispivottuple = (!leafpage || (!rightmost && offset == P_HIKEY));
+
+	/* LP_DEAD bit can never be set for pivot tuples, so show a NULL there */
+	if (!ispivottuple)
+		values[j++] = BoolGetDatum(ItemIdIsDead(id));
+	else
+	{
+		Assert(!ItemIdIsDead(id));
+		nulls[j++] = true;
+	}
+
+	htid = BTreeTupleGetHeapTID(itup);
+	if (ispivottuple && !BTreeTupleIsPivot(itup))
+	{
+		/* Don't show bogus heap TID in !heapkeyspace pivot tuple */
+		htid = NULL;
+	}
+
+	if (htid)
+		values[j++] = ItemPointerGetDatum(htid);
+	else
+		nulls[j++] = true;
+
+	if (BTreeTupleIsPosting(itup))
+	{
+		/* Build an array of item pointers */
+		ItemPointer tids;
+		Datum	   *tids_datum;
+		int			nposting;
+
+		tids = BTreeTupleGetPosting(itup);
+		nposting = BTreeTupleGetNPosting(itup);
+		tids_datum = (Datum *) palloc(nposting * sizeof(Datum));
+		for (int i = 0; i < nposting; i++)
+			tids_datum[i] = ItemPointerGetDatum(&tids[i]);
+		values[j++] = PointerGetDatum(construct_array(tids_datum,
+													  nposting,
+													  TIDOID,
+													  sizeof(ItemPointerData),
+													  false, 's'));
+		pfree(tids_datum);
+	}
+	else
+		nulls[j++] = true;
 
-	tuple = BuildTupleFromCStrings(fctx->attinmeta, values);
+	/* Build and return the result tuple */
+	tuple = heap_form_tuple(uargs->tupd, values, nulls);
 
 	return HeapTupleGetDatum(tuple);
 }
@@ -378,12 +478,15 @@ bt_page_items(PG_FUNCTION_ARGS)
 			elog(NOTICE, "page is deleted");
 
 		fctx->max_calls = PageGetMaxOffsetNumber(uargs->page);
+		uargs->leafpage = P_ISLEAF(opaque);
+		uargs->rightmost = P_RIGHTMOST(opaque);
 
 		/* Build a tuple descriptor for our result type */
 		if (get_call_result_type(fcinfo, NULL, &tupleDesc) != TYPEFUNC_COMPOSITE)
 			elog(ERROR, "return type must be a row type");
+		tupleDesc = BlessTupleDesc(tupleDesc);
 
-		fctx->attinmeta = TupleDescGetAttInMetadata(tupleDesc);
+		uargs->tupd = tupleDesc;
 
 		fctx->user_fctx = uargs;
 
@@ -395,7 +498,7 @@ bt_page_items(PG_FUNCTION_ARGS)
 
 	if (fctx->call_cntr < fctx->max_calls)
 	{
-		result = bt_page_print_tuples(fctx, uargs->page, uargs->offset);
+		result = bt_page_print_tuples(fctx, uargs);
 		uargs->offset++;
 		SRF_RETURN_NEXT(fctx, result);
 	}
@@ -463,12 +566,15 @@ bt_page_items_bytea(PG_FUNCTION_ARGS)
 			elog(NOTICE, "page is deleted");
 
 		fctx->max_calls = PageGetMaxOffsetNumber(uargs->page);
+		uargs->leafpage = P_ISLEAF(opaque);
+		uargs->rightmost = P_RIGHTMOST(opaque);
 
 		/* Build a tuple descriptor for our result type */
 		if (get_call_result_type(fcinfo, NULL, &tupleDesc) != TYPEFUNC_COMPOSITE)
 			elog(ERROR, "return type must be a row type");
+		tupleDesc = BlessTupleDesc(tupleDesc);
 
-		fctx->attinmeta = TupleDescGetAttInMetadata(tupleDesc);
+		uargs->tupd = tupleDesc;
 
 		fctx->user_fctx = uargs;
 
@@ -480,7 +586,7 @@ bt_page_items_bytea(PG_FUNCTION_ARGS)
 
 	if (fctx->call_cntr < fctx->max_calls)
 	{
-		result = bt_page_print_tuples(fctx, uargs->page, uargs->offset);
+		result = bt_page_print_tuples(fctx, uargs);
 		uargs->offset++;
 		SRF_RETURN_NEXT(fctx, result);
 	}
@@ -510,7 +616,7 @@ bt_metap(PG_FUNCTION_ARGS)
 	BTMetaPageData *metad;
 	TupleDesc	tupleDesc;
 	int			j;
-	char	   *values[8];
+	char	   *values[9];
 	Buffer		buffer;
 	Page		page;
 	HeapTuple	tuple;
@@ -557,17 +663,21 @@ bt_metap(PG_FUNCTION_ARGS)
 
 	/*
 	 * Get values of extended metadata if available, use default values
-	 * otherwise.
+	 * otherwise.  Note that we rely on the assumption that btm_allequalimage
+	 * is initialized to zero with indexes that were built on versions prior
+	 * to Postgres 13 (just like _bt_metaversion()).
 	 */
 	if (metad->btm_version >= BTREE_NOVAC_VERSION)
 	{
 		values[j++] = psprintf("%u", metad->btm_oldest_btpo_xact);
 		values[j++] = psprintf("%f", metad->btm_last_cleanup_num_heap_tuples);
+		values[j++] = metad->btm_allequalimage ? "t" : "f";
 	}
 	else
 	{
 		values[j++] = "0";
 		values[j++] = "-1";
+		values[j++] = "f";
 	}
 
 	tuple = BuildTupleFromCStrings(TupleDescGetAttInMetadata(tupleDesc),

contrib/pageinspect/expected/btree.out

@@ -12,6 +12,7 @@ fastroot                | 1
 fastlevel               | 0
 oldest_xact             | 0
 last_cleanup_num_tuples | -1
+allequalimage           | t
 
 SELECT * FROM bt_page_stats('test1_a_idx', 0);
 ERROR:  block 0 is a meta page
@@ -41,6 +42,9 @@ itemlen    | 16
 nulls      | f
 vars       | f
 data       | 01 00 00 00 00 00 00 01
+dead       | f
+htid       | (0,1)
+tids       | 
 
 SELECT * FROM bt_page_items('test1_a_idx', 2);
 ERROR:  block number out of range
@@ -54,6 +58,9 @@ itemlen    | 16
 nulls      | f
 vars       | f
 data       | 01 00 00 00 00 00 00 01
+dead       | f
+htid       | (0,1)
+tids       | 
 
 SELECT * FROM bt_page_items(get_raw_page('test1_a_idx', 2));
 ERROR:  block number 2 is out of range for relation "test1_a_idx"

contrib/pageinspect/pageinspect--1.7--1.8.sql

@@ -14,3 +14,56 @@ CREATE FUNCTION heap_tuple_infomask_flags(
 RETURNS record
 AS 'MODULE_PATHNAME', 'heap_tuple_infomask_flags'
 LANGUAGE C STRICT PARALLEL SAFE;
+
+--
+-- bt_metap()
+--
+DROP FUNCTION bt_metap(text);
+CREATE FUNCTION bt_metap(IN relname text,
+    OUT magic int4,
+    OUT version int4,
+    OUT root int4,
+    OUT level int4,
+    OUT fastroot int4,
+    OUT fastlevel int4,
+    OUT oldest_xact int4,
+    OUT last_cleanup_num_tuples real,
+    OUT allequalimage boolean)
+AS 'MODULE_PATHNAME', 'bt_metap'
+LANGUAGE C STRICT PARALLEL SAFE;
+
+--
+-- bt_page_items(text, int4)
+--
+DROP FUNCTION bt_page_items(text, int4);
+CREATE FUNCTION bt_page_items(IN relname text, IN blkno int4,
+    OUT itemoffset smallint,
+    OUT ctid tid,
+    OUT itemlen smallint,
+    OUT nulls bool,
+    OUT vars bool,
+    OUT data text,
+    OUT dead boolean,
+    OUT htid tid,
+    OUT tids tid[])
+RETURNS SETOF record
+AS 'MODULE_PATHNAME', 'bt_page_items'
+LANGUAGE C STRICT PARALLEL SAFE;
+
+--
+-- bt_page_items(bytea)
+--
+DROP FUNCTION bt_page_items(bytea);
+CREATE FUNCTION bt_page_items(IN page bytea,
+    OUT itemoffset smallint,
+    OUT ctid tid,
+    OUT itemlen smallint,
+    OUT nulls bool,
+    OUT vars bool,
+    OUT data text,
+    OUT dead boolean,
+    OUT htid tid,
+    OUT tids tid[])
+RETURNS SETOF record
+AS 'MODULE_PATHNAME', 'bt_page_items_bytea'
+LANGUAGE C STRICT PARALLEL SAFE;

doc/src/sgml/pageinspect.sgml

@@ -300,13 +300,14 @@ test=# SELECT t_ctid, raw_flags, combined_flags
 test=# SELECT * FROM bt_metap('pg_cast_oid_index');
 -[ RECORD 1 ]-----------+-------
 magic                   | 340322
-version                 | 3
+version                 | 4
 root                    | 1
 level                   | 0
 fastroot                | 1
 fastlevel               | 0
 oldest_xact             | 582
 last_cleanup_num_tuples | 1000
+allequalimage           | f
 </screen>
      </para>
     </listitem>
@@ -329,11 +330,11 @@ test=# SELECT * FROM bt_page_stats('pg_cast_oid_index', 1);
 -[ RECORD 1 ]-+-----
 blkno         | 1
 type          | l
-live_items    | 256
+live_items    | 224
 dead_items    | 0
-avg_item_size | 12
+avg_item_size | 16
 page_size     | 8192
-free_size     | 4056
+free_size     | 3668
 btpo_prev     | 0
 btpo_next     | 0
 btpo          | 0
@@ -356,33 +357,75 @@ btpo_flags    | 3
       <function>bt_page_items</function> returns detailed information about
       all of the items on a B-tree index page.  For example:
 <screen>
-test=# SELECT * FROM bt_page_items('pg_cast_oid_index', 1);
- itemoffset |  ctid   | itemlen | nulls | vars |    data
-------------+---------+---------+-------+------+-------------
-          1 | (0,1)   |      12 | f     | f    | 23 27 00 00
-          2 | (0,2)   |      12 | f     | f    | 24 27 00 00
-          3 | (0,3)   |      12 | f     | f    | 25 27 00 00
-          4 | (0,4)   |      12 | f     | f    | 26 27 00 00
-          5 | (0,5)   |      12 | f     | f    | 27 27 00 00
-          6 | (0,6)   |      12 | f     | f    | 28 27 00 00
-          7 | (0,7)   |      12 | f     | f    | 29 27 00 00
-          8 | (0,8)   |      12 | f     | f    | 2a 27 00 00
+ test=# SELECT itemoffset, ctid, itemlen, nulls, vars, data, dead, htid, tids[0:2] AS some_tids
+         FROM bt_page_items(get_raw_page('tenk2_hundred', 5));
+ itemoffset |   ctid    | itemlen | nulls | vars |          data           | dead |  htid  |      some_tids
+------------+-----------+---------+-------+------+-------------------------+------+--------+---------------------
+          1 | (16,1)    |      16 | f     | f    | 30 00 00 00 00 00 00 00 |      |        |
+          2 | (16,8292) |     616 | f     | f    | 24 00 00 00 00 00 00 00 | f    | (1,6)  | {"(1,6)","(10,22)"}
+          3 | (16,8292) |     616 | f     | f    | 25 00 00 00 00 00 00 00 | f    | (1,18) | {"(1,18)","(4,22)"}
+          4 | (16,8292) |     616 | f     | f    | 26 00 00 00 00 00 00 00 | f    | (4,18) | {"(4,18)","(6,17)"}
+          5 | (16,8292) |     616 | f     | f    | 27 00 00 00 00 00 00 00 | f    | (1,2)  | {"(1,2)","(1,19)"}
+          6 | (16,8292) |     616 | f     | f    | 28 00 00 00 00 00 00 00 | f    | (2,24) | {"(2,24)","(4,11)"}
+          7 | (16,8292) |     616 | f     | f    | 29 00 00 00 00 00 00 00 | f    | (2,17) | {"(2,17)","(11,2)"}
+          8 | (16,8292) |     616 | f     | f    | 2a 00 00 00 00 00 00 00 | f    | (0,25) | {"(0,25)","(3,20)"}
+          9 | (16,8292) |     616 | f     | f    | 2b 00 00 00 00 00 00 00 | f    | (0,10) | {"(0,10)","(0,14)"}
+         10 | (16,8292) |     616 | f     | f    | 2c 00 00 00 00 00 00 00 | f    | (1,3)  | {"(1,3)","(3,9)"}
+         11 | (16,8292) |     616 | f     | f    | 2d 00 00 00 00 00 00 00 | f    | (6,28) | {"(6,28)","(11,1)"}
+         12 | (16,8292) |     616 | f     | f    | 2e 00 00 00 00 00 00 00 | f    | (0,27) | {"(0,27)","(1,13)"}
+         13 | (16,8292) |     616 | f     | f    | 2f 00 00 00 00 00 00 00 | f    | (4,17) | {"(4,17)","(4,21)"}
+(13 rows)
 </screen>
-      In a B-tree leaf page, <structfield>ctid</structfield> points to a heap tuple.
-      In an internal page, the block number part of <structfield>ctid</structfield>
-      points to another page in the index itself, while the offset part
-      (the second number) is ignored and is usually 1.
+      This is a B-tree leaf page.  All tuples that point to the table
+      happen to be posting list tuples (all of which store a total of
+      100 6 byte TIDs).  There is also a <quote>high key</quote> tuple
+      at <literal>itemoffset</literal> number 1.
+      <structfield>ctid</structfield> is used to store encoded
+      information about each tuple in this example, though leaf page
+      tuples often store a heap TID directly in the
+      <structfield>ctid</structfield> field instead.
+      <structfield>tids</structfield> is the list of TIDs stored as a
+      posting list.
+     </para>
+     <para>
+      In an internal page (not shown), the block number part of
+      <structfield>ctid</structfield> is a <quote>downlink</quote>,
+      which is a block number of another page in the index itself.
+      The offset part (the second number) of
+      <structfield>ctid</structfield> stores encoded information about
+      the tuple, such as the number of columns present (suffix
+      truncation may have removed unneeded suffix columns).  Truncated
+      columns are treated as having the value <quote>minus
+       infinity</quote>.
+     </para>
+     <para>
+      <structfield>htid</structfield> shows a heap TID for the tuple,
+      regardless of the underlying tuple representation.  This value
+      may match <structfield>ctid</structfield>, or may be decoded
+      from the alternative representations used by posting list tuples
+      and tuples from internal pages.  Tuples in internal pages
+      usually have the implementation level heap TID column truncated
+      away, which is represented as a NULL
+      <structfield>htid</structfield> value.
      </para>
      <para>
       Note that the first item on any non-rightmost page (any page with
       a non-zero value in the <structfield>btpo_next</structfield> field) is the
       page's <quote>high key</quote>, meaning its <structfield>data</structfield>
       serves as an upper bound on all items appearing on the page, while
-      its <structfield>ctid</structfield> field is meaningless.  Also, on non-leaf
-      pages, the first real data item (the first item that is not a high
-      key) is a <quote>minus infinity</quote> item, with no actual value
-      in its <structfield>data</structfield> field.  Such an item does have a valid
-      downlink in its <structfield>ctid</structfield> field, however.
+      its <structfield>ctid</structfield> field does not point to
+      another block.  Also, on internal pages, the first real data
+      item (the first item that is not a high key) reliably has every
+      column truncated away, leaving no actual value in its
+      <structfield>data</structfield> field.  Such an item does have a
+      valid downlink in its <structfield>ctid</structfield> field,
+      however.
+     </para>
+     <para>
+      For more details about the structure of B-tree indexes, see
+      <xref linkend="btree-structure"/>.  For more details about
+      deduplication and posting lists, see <xref
+       linkend="btree-deduplication"/>.
      </para>
     </listitem>
    </varlistentry>
@@ -402,17 +445,24 @@ test=# SELECT * FROM bt_page_items('pg_cast_oid_index', 1);
       with <function>get_raw_page</function> should be passed as argument.  So
       the last example could also be rewritten like this:
 <screen>
-test=# SELECT * FROM bt_page_items(get_raw_page('pg_cast_oid_index', 1));
- itemoffset |  ctid   | itemlen | nulls | vars |    data
-------------+---------+---------+-------+------+-------------
-          1 | (0,1)   |      12 | f     | f    | 23 27 00 00
-          2 | (0,2)   |      12 | f     | f    | 24 27 00 00
-          3 | (0,3)   |      12 | f     | f    | 25 27 00 00
-          4 | (0,4)   |      12 | f     | f    | 26 27 00 00
-          5 | (0,5)   |      12 | f     | f    | 27 27 00 00
-          6 | (0,6)   |      12 | f     | f    | 28 27 00 00
-          7 | (0,7)   |      12 | f     | f    | 29 27 00 00
-          8 | (0,8)   |      12 | f     | f    | 2a 27 00 00
+ test=# SELECT itemoffset, ctid, itemlen, nulls, vars, data, dead, htid, tids[0:2] AS some_tids
+         FROM bt_page_items(get_raw_page('tenk2_hundred', 5));
+ itemoffset |   ctid    | itemlen | nulls | vars |          data           | dead |  htid  |      some_tids
+------------+-----------+---------+-------+------+-------------------------+------+--------+---------------------
+          1 | (16,1)    |      16 | f     | f    | 30 00 00 00 00 00 00 00 |      |        |
+          2 | (16,8292) |     616 | f     | f    | 24 00 00 00 00 00 00 00 | f    | (1,6)  | {"(1,6)","(10,22)"}
+          3 | (16,8292) |     616 | f     | f    | 25 00 00 00 00 00 00 00 | f    | (1,18) | {"(1,18)","(4,22)"}
+          4 | (16,8292) |     616 | f     | f    | 26 00 00 00 00 00 00 00 | f    | (4,18) | {"(4,18)","(6,17)"}
+          5 | (16,8292) |     616 | f     | f    | 27 00 00 00 00 00 00 00 | f    | (1,2)  | {"(1,2)","(1,19)"}
+          6 | (16,8292) |     616 | f     | f    | 28 00 00 00 00 00 00 00 | f    | (2,24) | {"(2,24)","(4,11)"}
+          7 | (16,8292) |     616 | f     | f    | 29 00 00 00 00 00 00 00 | f    | (2,17) | {"(2,17)","(11,2)"}
+          8 | (16,8292) |     616 | f     | f    | 2a 00 00 00 00 00 00 00 | f    | (0,25) | {"(0,25)","(3,20)"}
+          9 | (16,8292) |     616 | f     | f    | 2b 00 00 00 00 00 00 00 | f    | (0,10) | {"(0,10)","(0,14)"}
+         10 | (16,8292) |     616 | f     | f    | 2c 00 00 00 00 00 00 00 | f    | (1,3)  | {"(1,3)","(3,9)"}
+         11 | (16,8292) |     616 | f     | f    | 2d 00 00 00 00 00 00 00 | f    | (6,28) | {"(6,28)","(11,1)"}
+         12 | (16,8292) |     616 | f     | f    | 2e 00 00 00 00 00 00 00 | f    | (0,27) | {"(0,27)","(1,13)"}
+         13 | (16,8292) |     616 | f     | f    | 2f 00 00 00 00 00 00 00 | f    | (4,17) | {"(4,17)","(4,21)"}
+(13 rows)
 </screen>
       All the other details are the same as explained in the previous item.
      </para>