Add to pageinspect function to make t_infomask/t_infomask2 human-readable

Flags of t_infomask and t_infomask2 for each tuple are already included
in the information returned by heap_page_items as integers, and we
lacked a way to make that information human-readable.

Per discussion, the function includes an option which controls if
combined flags should be decomposed or not.  The default is false, to
not decompose combined flags.

The module is bumped to version 1.8.

Author: Craig Ringer, Sawada Masahiko
Reviewed-by: Peter Geoghegan, Robert Haas, Álvaro Herrera, Moon Insung,
Amit Kapila, Michael Paquier, Tomas Vondra
Discussion: https://postgr.es/m/CAMsr+YEY7jeaXOb+oX+RhDyOFuTMdmHjGsBxL=igCm03J0go9Q@mail.gmail.com

contrib/pageinspect/Makefile

@@ -5,7 +5,7 @@ OBJS		= rawpage.o heapfuncs.o btreefuncs.o fsmfuncs.o \
 		  brinfuncs.o ginfuncs.o hashfuncs.o $(WIN32RES)
 
 EXTENSION = pageinspect
-DATA =  pageinspect--1.6--1.7.sql \
+DATA =  pageinspect--1.7--1.8.sql pageinspect--1.6--1.7.sql \
 	pageinspect--1.5.sql pageinspect--1.5--1.6.sql \
 	pageinspect--1.4--1.5.sql pageinspect--1.3--1.4.sql \
 	pageinspect--1.2--1.3.sql pageinspect--1.1--1.2.sql \

contrib/pageinspect/expected/page.out

@@ -82,6 +82,186 @@ SELECT * FROM fsm_page_contents(get_raw_page('test1', 'fsm', 0));
  
 (1 row)
 
+-- If we freeze the only tuple on test1, the infomask should
+-- always be the same in all test runs. we show raw flags by
+-- default: HEAP_XMIN_COMMITTED and HEAP_XMIN_INVALID.
+VACUUM FREEZE test1;
+SELECT t_infomask, t_infomask2, flags
+FROM heap_page_items(get_raw_page('test1', 0)),
+     LATERAL heap_tuple_infomask_flags(t_infomask, t_infomask2) m(flags);
+ t_infomask | t_infomask2 |                           flags                           
+------------+-------------+-----------------------------------------------------------
+       2816 |           2 | {HEAP_XMAX_INVALID,HEAP_XMIN_COMMITTED,HEAP_XMIN_INVALID}
+(1 row)
+
+-- output the decoded flag HEAP_XMIN_FROZEN instead
+SELECT t_infomask, t_infomask2, flags
+FROM heap_page_items(get_raw_page('test1', 0)),
+     LATERAL heap_tuple_infomask_flags(t_infomask, t_infomask2, true) m(flags);
+ t_infomask | t_infomask2 |                flags                 
+------------+-------------+--------------------------------------
+       2816 |           2 | {HEAP_XMAX_INVALID,HEAP_XMIN_FROZEN}
+(1 row)
+
+-- tests for decoding of combined flags
+-- HEAP_XMAX_SHR_LOCK = (HEAP_XMAX_EXCL_LOCK | HEAP_XMAX_KEYSHR_LOCK)
+SELECT heap_tuple_infomask_flags(x'0050'::int, 0, true);
+ heap_tuple_infomask_flags 
+---------------------------
+ {HEAP_XMAX_SHR_LOCK}
+(1 row)
+
+SELECT heap_tuple_infomask_flags(x'0050'::int, 0, false);
+          heap_tuple_infomask_flags          
+---------------------------------------------
+ {HEAP_XMAX_EXCL_LOCK,HEAP_XMAX_KEYSHR_LOCK}
+(1 row)
+
+-- HEAP_XMIN_FROZEN = (HEAP_XMIN_COMMITTED | HEAP_XMIN_INVALID)
+SELECT heap_tuple_infomask_flags(x'0300'::int, 0, true);
+ heap_tuple_infomask_flags 
+---------------------------
+ {HEAP_XMIN_FROZEN}
+(1 row)
+
+SELECT heap_tuple_infomask_flags(x'0300'::int, 0, false);
+        heap_tuple_infomask_flags        
+-----------------------------------------
+ {HEAP_XMIN_COMMITTED,HEAP_XMIN_INVALID}
+(1 row)
+
+-- HEAP_MOVED = (HEAP_MOVED_IN | HEAP_MOVED_OFF)
+SELECT heap_tuple_infomask_flags(x'C000'::int, 0, true);
+ heap_tuple_infomask_flags 
+---------------------------
+ {HEAP_MOVED}
+(1 row)
+
+SELECT heap_tuple_infomask_flags(x'C000'::int, 0, false);
+   heap_tuple_infomask_flags    
+--------------------------------
+ {HEAP_MOVED_IN,HEAP_MOVED_OFF}
+(1 row)
+
+-- HEAP_LOCKED_UPGRADED = (HEAP_XMAX_IS_MULTI | HEAP_XMAX_LOCK_ONLY)
+SELECT heap_tuple_infomask_flags(x'1080'::int, 0, true);
+ heap_tuple_infomask_flags 
+---------------------------
+ {HEAP_LOCKED_UPGRADED}
+(1 row)
+
+SELECT heap_tuple_infomask_flags(x'1080'::int, 0, false);
+        heap_tuple_infomask_flags         
+------------------------------------------
+ {HEAP_XMAX_LOCK_ONLY,HEAP_XMAX_IS_MULTI}
+(1 row)
+
+-- test all flags of t_infomask and t_infomask2
+SELECT unnest(heap_tuple_infomask_flags(x'FFFF'::int, x'FFFF'::int, false))
+  AS flags ORDER BY 1;
+         flags         
+-----------------------
+ HEAP_COMBOCID
+ HEAP_HASEXTERNAL
+ HEAP_HASNULL
+ HEAP_HASOID_OLD
+ HEAP_HASVARWIDTH
+ HEAP_HOT_UPDATED
+ HEAP_KEYS_UPDATED
+ HEAP_MOVED_IN
+ HEAP_MOVED_OFF
+ HEAP_ONLY_TUPLE
+ HEAP_UPDATED
+ HEAP_XMAX_COMMITTED
+ HEAP_XMAX_EXCL_LOCK
+ HEAP_XMAX_INVALID
+ HEAP_XMAX_IS_MULTI
+ HEAP_XMAX_KEYSHR_LOCK
+ HEAP_XMAX_LOCK_ONLY
+ HEAP_XMIN_COMMITTED
+ HEAP_XMIN_INVALID
+(19 rows)
+
+SELECT unnest(heap_tuple_infomask_flags(x'FFFF'::int, x'FFFF'::int, true))
+  AS flags ORDER BY 1;
+        flags        
+---------------------
+ HEAP_COMBOCID
+ HEAP_HASEXTERNAL
+ HEAP_HASNULL
+ HEAP_HASOID_OLD
+ HEAP_HASVARWIDTH
+ HEAP_HOT_UPDATED
+ HEAP_KEYS_UPDATED
+ HEAP_MOVED
+ HEAP_ONLY_TUPLE
+ HEAP_UPDATED
+ HEAP_XMAX_COMMITTED
+ HEAP_XMAX_INVALID
+ HEAP_XMAX_IS_MULTI
+ HEAP_XMAX_LOCK_ONLY
+ HEAP_XMAX_SHR_LOCK
+ HEAP_XMIN_FROZEN
+(16 rows)
+
+SELECT unnest(heap_tuple_infomask_flags(-1, -1, false))
+  AS flags ORDER BY 1;
+         flags         
+-----------------------
+ HEAP_COMBOCID
+ HEAP_HASEXTERNAL
+ HEAP_HASNULL
+ HEAP_HASOID_OLD
+ HEAP_HASVARWIDTH
+ HEAP_HOT_UPDATED
+ HEAP_KEYS_UPDATED
+ HEAP_MOVED_IN
+ HEAP_MOVED_OFF
+ HEAP_ONLY_TUPLE
+ HEAP_UPDATED
+ HEAP_XMAX_COMMITTED
+ HEAP_XMAX_EXCL_LOCK
+ HEAP_XMAX_INVALID
+ HEAP_XMAX_IS_MULTI
+ HEAP_XMAX_KEYSHR_LOCK
+ HEAP_XMAX_LOCK_ONLY
+ HEAP_XMIN_COMMITTED
+ HEAP_XMIN_INVALID
+(19 rows)
+
+SELECT unnest(heap_tuple_infomask_flags(-1, -1, true))
+  AS flags ORDER BY 1;
+        flags        
+---------------------
+ HEAP_COMBOCID
+ HEAP_HASEXTERNAL
+ HEAP_HASNULL
+ HEAP_HASOID_OLD
+ HEAP_HASVARWIDTH
+ HEAP_HOT_UPDATED
+ HEAP_KEYS_UPDATED
+ HEAP_MOVED
+ HEAP_ONLY_TUPLE
+ HEAP_UPDATED
+ HEAP_XMAX_COMMITTED
+ HEAP_XMAX_INVALID
+ HEAP_XMAX_IS_MULTI
+ HEAP_XMAX_LOCK_ONLY
+ HEAP_XMAX_SHR_LOCK
+ HEAP_XMIN_FROZEN
+(16 rows)
+
+-- no flags
+SELECT unnest(heap_tuple_infomask_flags(0, 0, false));
+ unnest 
+--------
+(0 rows)
+
+SELECT unnest(heap_tuple_infomask_flags(0, 0, true));
+ unnest 
+--------
+(0 rows)
+
 DROP TABLE test1;
 -- check that using any of these functions with a partitioned table or index
 -- would fail

contrib/pageinspect/heapfuncs.c

@@ -33,6 +33,7 @@
 #include "catalog/pg_am_d.h"
 #include "catalog/pg_type.h"
 #include "miscadmin.h"
+#include "port/pg_bitutils.h"
 #include "utils/array.h"
 #include "utils/builtins.h"
 #include "utils/rel.h"
@@ -494,3 +495,111 @@ tuple_data_split(PG_FUNCTION_ARGS)
 
 	PG_RETURN_ARRAYTYPE_P(res);
 }
+
+/*
+ * heap_tuple_infomask_flags
+ *
+ * Decode into a human-readable format t_infomask and t_infomask2 associated
+ * to a tuple.  All the flags are described in access/htup_details.h.
+ */
+PG_FUNCTION_INFO_V1(heap_tuple_infomask_flags);
+
+Datum
+heap_tuple_infomask_flags(PG_FUNCTION_ARGS)
+{
+	uint16		t_infomask = PG_GETARG_INT16(0);
+	uint16		t_infomask2 = PG_GETARG_INT16(1);
+	bool		decode_combined = PG_GETARG_BOOL(2);
+	int			cnt = 0;
+	ArrayType  *a;
+	int			bitcnt;
+	Datum	   *d;
+
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("must be superuser to use raw page functions")));
+
+	bitcnt = pg_popcount((const char *) &t_infomask, sizeof(uint16)) +
+		pg_popcount((const char *) &t_infomask2, sizeof(uint16));
+
+	/* If no flags, return an empty array */
+	if (bitcnt <= 0)
+		PG_RETURN_POINTER(construct_empty_array(TEXTOID));
+
+	d = (Datum *) palloc0(sizeof(Datum) * bitcnt);
+
+	/* decode t_infomask */
+	if ((t_infomask & HEAP_HASNULL) != 0)
+		d[cnt++] = CStringGetTextDatum("HEAP_HASNULL");
+	if ((t_infomask & HEAP_HASVARWIDTH) != 0)
+		d[cnt++] = CStringGetTextDatum("HEAP_HASVARWIDTH");
+	if ((t_infomask & HEAP_HASEXTERNAL) != 0)
+		d[cnt++] = CStringGetTextDatum("HEAP_HASEXTERNAL");
+	if ((t_infomask & HEAP_HASOID_OLD) != 0)
+		d[cnt++] = CStringGetTextDatum("HEAP_HASOID_OLD");
+	if ((t_infomask & HEAP_COMBOCID) != 0)
+		d[cnt++] = CStringGetTextDatum("HEAP_COMBOCID");
+	if ((t_infomask & HEAP_XMAX_COMMITTED) != 0)
+		d[cnt++] = CStringGetTextDatum("HEAP_XMAX_COMMITTED");
+	if ((t_infomask & HEAP_XMAX_INVALID) != 0)
+		d[cnt++] = CStringGetTextDatum("HEAP_XMAX_INVALID");
+	if ((t_infomask & HEAP_UPDATED) != 0)
+		d[cnt++] = CStringGetTextDatum("HEAP_UPDATED");
+
+	/* decode combined masks of t_infomaks */
+	if (decode_combined && (t_infomask & HEAP_XMAX_SHR_LOCK) != 0)
+		d[cnt++] = CStringGetTextDatum("HEAP_XMAX_SHR_LOCK");
+	else
+	{
+		if ((t_infomask & HEAP_XMAX_EXCL_LOCK) != 0)
+			d[cnt++] = CStringGetTextDatum("HEAP_XMAX_EXCL_LOCK");
+		if ((t_infomask & HEAP_XMAX_KEYSHR_LOCK) != 0)
+			d[cnt++] = CStringGetTextDatum("HEAP_XMAX_KEYSHR_LOCK");
+	}
+
+	if (decode_combined && (t_infomask & HEAP_XMIN_FROZEN) != 0)
+		d[cnt++] = CStringGetTextDatum("HEAP_XMIN_FROZEN");
+	else
+	{
+		if ((t_infomask & HEAP_XMIN_COMMITTED) != 0)
+			d[cnt++] = CStringGetTextDatum("HEAP_XMIN_COMMITTED");
+		if ((t_infomask & HEAP_XMIN_INVALID) != 0)
+			d[cnt++] = CStringGetTextDatum("HEAP_XMIN_INVALID");
+	}
+
+	if (decode_combined && (t_infomask & HEAP_MOVED) != 0)
+		d[cnt++] = CStringGetTextDatum("HEAP_MOVED");
+	else
+	{
+		if ((t_infomask & HEAP_MOVED_IN) != 0)
+			d[cnt++] = CStringGetTextDatum("HEAP_MOVED_IN");
+		if ((t_infomask & HEAP_MOVED_OFF) != 0)
+			d[cnt++] = CStringGetTextDatum("HEAP_MOVED_OFF");
+	}
+
+	if (decode_combined && HEAP_LOCKED_UPGRADED(t_infomask))
+		d[cnt++] = CStringGetTextDatum("HEAP_LOCKED_UPGRADED");
+	else
+	{
+		if (HEAP_XMAX_IS_LOCKED_ONLY(t_infomask))
+			d[cnt++] = CStringGetTextDatum("HEAP_XMAX_LOCK_ONLY");
+		if ((t_infomask & HEAP_XMAX_IS_MULTI) != 0)
+			d[cnt++] = CStringGetTextDatum("HEAP_XMAX_IS_MULTI");
+	}
+
+	/* decode t_infomask2 */
+	if ((t_infomask2 & HEAP_KEYS_UPDATED) != 0)
+		d[cnt++] = CStringGetTextDatum("HEAP_KEYS_UPDATED");
+	if ((t_infomask2 & HEAP_HOT_UPDATED) != 0)
+		d[cnt++] = CStringGetTextDatum("HEAP_HOT_UPDATED");
+	if ((t_infomask2 & HEAP_ONLY_TUPLE) != 0)
+		d[cnt++] = CStringGetTextDatum("HEAP_ONLY_TUPLE");
+
+	Assert(cnt <= bitcnt);
+	a = construct_array(d, cnt, TEXTOID, -1, false, 'i');
+
+	pfree(d);
+
+	PG_RETURN_POINTER(a);
+}

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

@@ -0,0 +1,15 @@
+/* contrib/pageinspect/pageinspect--1.7--1.8.sql */
+
+-- complain if script is sourced in psql, rather than via ALTER EXTENSION
+\echo Use "ALTER EXTENSION pageinspect UPDATE TO '1.8'" to load this file. \quit
+
+--
+-- heap_tuple_infomask_flags()
+--
+CREATE FUNCTION heap_tuple_infomask_flags(
+       t_infomask integer,
+       t_infomask2 integer,
+       decode_combined boolean DEFAULT false)
+RETURNS text[]
+AS 'MODULE_PATHNAME', 'heap_tuple_infomask_flags'
+LANGUAGE C STRICT PARALLEL SAFE;

contrib/pageinspect/pageinspect.control

@@ -1,5 +1,5 @@
 # pageinspect extension
 comment = 'inspect the contents of database pages at a low level'
-default_version = '1.7'
+default_version = '1.8'
 module_pathname = '$libdir/pageinspect'
 relocatable = true

contrib/pageinspect/sql/page.sql

@@ -31,6 +31,48 @@ SELECT tuple_data_split('test1'::regclass, t_data, t_infomask, t_infomask2, t_bi
 
 SELECT * FROM fsm_page_contents(get_raw_page('test1', 'fsm', 0));
 
+-- If we freeze the only tuple on test1, the infomask should
+-- always be the same in all test runs. we show raw flags by
+-- default: HEAP_XMIN_COMMITTED and HEAP_XMIN_INVALID.
+VACUUM FREEZE test1;
+
+SELECT t_infomask, t_infomask2, flags
+FROM heap_page_items(get_raw_page('test1', 0)),
+     LATERAL heap_tuple_infomask_flags(t_infomask, t_infomask2) m(flags);
+
+-- output the decoded flag HEAP_XMIN_FROZEN instead
+SELECT t_infomask, t_infomask2, flags
+FROM heap_page_items(get_raw_page('test1', 0)),
+     LATERAL heap_tuple_infomask_flags(t_infomask, t_infomask2, true) m(flags);
+
+-- tests for decoding of combined flags
+-- HEAP_XMAX_SHR_LOCK = (HEAP_XMAX_EXCL_LOCK | HEAP_XMAX_KEYSHR_LOCK)
+SELECT heap_tuple_infomask_flags(x'0050'::int, 0, true);
+SELECT heap_tuple_infomask_flags(x'0050'::int, 0, false);
+-- HEAP_XMIN_FROZEN = (HEAP_XMIN_COMMITTED | HEAP_XMIN_INVALID)
+SELECT heap_tuple_infomask_flags(x'0300'::int, 0, true);
+SELECT heap_tuple_infomask_flags(x'0300'::int, 0, false);
+-- HEAP_MOVED = (HEAP_MOVED_IN | HEAP_MOVED_OFF)
+SELECT heap_tuple_infomask_flags(x'C000'::int, 0, true);
+SELECT heap_tuple_infomask_flags(x'C000'::int, 0, false);
+-- HEAP_LOCKED_UPGRADED = (HEAP_XMAX_IS_MULTI | HEAP_XMAX_LOCK_ONLY)
+SELECT heap_tuple_infomask_flags(x'1080'::int, 0, true);
+SELECT heap_tuple_infomask_flags(x'1080'::int, 0, false);
+
+-- test all flags of t_infomask and t_infomask2
+SELECT unnest(heap_tuple_infomask_flags(x'FFFF'::int, x'FFFF'::int, false))
+  AS flags ORDER BY 1;
+SELECT unnest(heap_tuple_infomask_flags(x'FFFF'::int, x'FFFF'::int, true))
+  AS flags ORDER BY 1;
+SELECT unnest(heap_tuple_infomask_flags(-1, -1, false))
+  AS flags ORDER BY 1;
+SELECT unnest(heap_tuple_infomask_flags(-1, -1, true))
+  AS flags ORDER BY 1;
+
+-- no flags
+SELECT unnest(heap_tuple_infomask_flags(0, 0, false));
+SELECT unnest(heap_tuple_infomask_flags(0, 0, true));
+
 DROP TABLE test1;
 
 -- check that using any of these functions with a partitioned table or index

doc/src/sgml/pageinspect.sgml

@@ -184,6 +184,11 @@ test=# SELECT * FROM heap_page_items(get_raw_page('pg_class', 0));
       <filename>src/include/access/htup_details.h</filename> for explanations of the fields
       returned.
      </para>
+     <para>
+      The <function>heap_tuple_infomask_flags</function> function can be
+      used to unpack the flag bits of <structfield>t_infomask</structfield>
+      and <structfield>t_infomask2</structfield> for heap tuples.
+     </para>
     </listitem>
    </varlistentry>
 
@@ -236,6 +241,42 @@ test=# SELECT * FROM heap_page_item_attrs(get_raw_page('pg_class', 0), 'pg_class
      </para>
     </listitem>
    </varlistentry>
+
+   <varlistentry>
+    <term>
+     <function>heap_tuple_infomask_flags(t_infomask integer, t_infomask2 integer, decode_combined bool) returns text[]</function>
+     <indexterm>
+      <primary>heap_tuple_infomask_flags</primary>
+     </indexterm>
+    </term>
+    <listitem>
+     <para>
+      <function>heap_tuple_infomask_flags</function> decodes the
+      <structfield>t_infomask</structfield> and
+      <structfield>t_infomask2</structfield> returned by
+      <function>heap_page_items</function> into a human-readable
+      array of flag names.  For example:
+<screen>
+test=# SELECT t_ctid, heap_tuple_infomask_flags(t_infomask, t_infomask2) AS flags
+         FROM heap_page_items(get_raw_page('pg_class', 0))
+         WHERE t_infomask IS NOT NULL OR t_infomask2 IS NOT NULL;
+</screen>
+      This function should be called with the same arguments as the return
+      attributes of <function>heap_page_items</function>.
+     </para>
+     <para>
+      If <parameter>decode_combined</parameter> is <literal>true</literal>,
+      combined flags like <literal>HEAP_XMIN_FROZEN</literal> are
+      returned instead of raw flags (<literal>HEAP_XMIN_COMMITTED</literal>
+      and <literal>HEAP_XMIN_INVALID</literal> in this case). Default value
+      is <literal>false</literal>.
+     </para>
+     <para>
+      See <filename>src/include/access/htup_details.h</filename> for
+      explanations of the flag names returned.
+     </para>
+    </listitem>
+   </varlistentry>
   </variablelist>
  </sect2>