1 /*-------------------------------------------------------------------------
2  *
3  * heapfuncs.c
4  *	  Functions to investigate heap pages
5  *
6  * We check the input to these functions for corrupt pointers etc. that
7  * might cause crashes, but at the same time we try to print out as much
8  * information as possible, even if it's nonsense. That's because if a
9  * page is corrupt, we don't know why and how exactly it is corrupt, so we
10  * let the user judge it.
11  *
12  * These functions are restricted to superusers for the fear of introducing
13  * security holes if the input checking isn't as water-tight as it should be.
14  * You'd need to be superuser to obtain a raw page image anyway, so
15  * there's hardly any use case for using these without superuser-rights
16  * anyway.
17  *
18  * Copyright (c) 2007-2021, PostgreSQL Global Development Group
19  *
20  * IDENTIFICATION
21  *	  contrib/pageinspect/heapfuncs.c
22  *
23  *-------------------------------------------------------------------------
24  */
25 
26 #include "postgres.h"
27 
28 #include "access/htup_details.h"
29 #include "access/relation.h"
30 #include "catalog/pg_am_d.h"
31 #include "catalog/pg_type.h"
32 #include "funcapi.h"
33 #include "mb/pg_wchar.h"
34 #include "miscadmin.h"
35 #include "pageinspect.h"
36 #include "port/pg_bitutils.h"
37 #include "utils/array.h"
38 #include "utils/builtins.h"
39 #include "utils/rel.h"
40 
41 /*
42  * It's not supported to create tuples with oids anymore, but when pg_upgrade
43  * was used to upgrade from an older version, tuples might still have an
44  * oid. Seems worthwhile to display that.
45  */
46 #define HeapTupleHeaderGetOidOld(tup) \
47 ( \
48 	((tup)->t_infomask & HEAP_HASOID_OLD) ? \
49 	   *((Oid *) ((char *)(tup) + (tup)->t_hoff - sizeof(Oid))) \
50 	: \
51 		InvalidOid \
52 )
53 
54 
55 /*
56  * bits_to_text
57  *
58  * Converts a bits8-array of 'len' bits to a human-readable
59  * c-string representation.
60  */
61 static char *
bits_to_text(bits8 * bits,int len)62 bits_to_text(bits8 *bits, int len)
63 {
64 	int			i;
65 	char	   *str;
66 
67 	str = palloc(len + 1);
68 
69 	for (i = 0; i < len; i++)
70 		str[i] = (bits[(i / 8)] & (1 << (i % 8))) ? '1' : '0';
71 
72 	str[i] = '\0';
73 
74 	return str;
75 }
76 
77 
78 /*
79  * text_to_bits
80  *
81  * Converts a c-string representation of bits into a bits8-array. This is
82  * the reverse operation of previous routine.
83  */
84 static bits8 *
text_to_bits(char * str,int len)85 text_to_bits(char *str, int len)
86 {
87 	bits8	   *bits;
88 	int			off = 0;
89 	char		byte = 0;
90 
91 	bits = palloc(len + 1);
92 
93 	while (off < len)
94 	{
95 		if (off % 8 == 0)
96 			byte = 0;
97 
98 		if ((str[off] == '0') || (str[off] == '1'))
99 			byte = byte | ((str[off] - '0') << off % 8);
100 		else
101 			ereport(ERROR,
102 					(errcode(ERRCODE_DATA_CORRUPTED),
103 					 errmsg("invalid character \"%.*s\" in t_bits string",
104 							pg_mblen(str + off), str + off)));
105 
106 		if (off % 8 == 7)
107 			bits[off / 8] = byte;
108 
109 		off++;
110 	}
111 
112 	return bits;
113 }
114 
115 /*
116  * heap_page_items
117  *
118  * Allows inspection of line pointers and tuple headers of a heap page.
119  */
120 PG_FUNCTION_INFO_V1(heap_page_items);
121 
122 typedef struct heap_page_items_state
123 {
124 	TupleDesc	tupd;
125 	Page		page;
126 	uint16		offset;
127 } heap_page_items_state;
128 
129 Datum
heap_page_items(PG_FUNCTION_ARGS)130 heap_page_items(PG_FUNCTION_ARGS)
131 {
132 	bytea	   *raw_page = PG_GETARG_BYTEA_P(0);
133 	heap_page_items_state *inter_call_data = NULL;
134 	FuncCallContext *fctx;
135 	int			raw_page_size;
136 
137 	if (!superuser())
138 		ereport(ERROR,
139 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
140 				 errmsg("must be superuser to use raw page functions")));
141 
142 	raw_page_size = VARSIZE(raw_page) - VARHDRSZ;
143 
144 	if (SRF_IS_FIRSTCALL())
145 	{
146 		TupleDesc	tupdesc;
147 		MemoryContext mctx;
148 
149 		if (raw_page_size < SizeOfPageHeaderData)
150 			ereport(ERROR,
151 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
152 					 errmsg("input page too small (%d bytes)", raw_page_size)));
153 
154 		fctx = SRF_FIRSTCALL_INIT();
155 		mctx = MemoryContextSwitchTo(fctx->multi_call_memory_ctx);
156 
157 		inter_call_data = palloc(sizeof(heap_page_items_state));
158 
159 		/* Build a tuple descriptor for our result type */
160 		if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
161 			elog(ERROR, "return type must be a row type");
162 
163 		inter_call_data->tupd = tupdesc;
164 
165 		inter_call_data->offset = FirstOffsetNumber;
166 		inter_call_data->page = VARDATA(raw_page);
167 
168 		fctx->max_calls = PageGetMaxOffsetNumber(inter_call_data->page);
169 		fctx->user_fctx = inter_call_data;
170 
171 		MemoryContextSwitchTo(mctx);
172 	}
173 
174 	fctx = SRF_PERCALL_SETUP();
175 	inter_call_data = fctx->user_fctx;
176 
177 	if (fctx->call_cntr < fctx->max_calls)
178 	{
179 		Page		page = inter_call_data->page;
180 		HeapTuple	resultTuple;
181 		Datum		result;
182 		ItemId		id;
183 		Datum		values[14];
184 		bool		nulls[14];
185 		uint16		lp_offset;
186 		uint16		lp_flags;
187 		uint16		lp_len;
188 
189 		memset(nulls, 0, sizeof(nulls));
190 
191 		/* Extract information from the line pointer */
192 
193 		id = PageGetItemId(page, inter_call_data->offset);
194 
195 		lp_offset = ItemIdGetOffset(id);
196 		lp_flags = ItemIdGetFlags(id);
197 		lp_len = ItemIdGetLength(id);
198 
199 		values[0] = UInt16GetDatum(inter_call_data->offset);
200 		values[1] = UInt16GetDatum(lp_offset);
201 		values[2] = UInt16GetDatum(lp_flags);
202 		values[3] = UInt16GetDatum(lp_len);
203 
204 		/*
205 		 * We do just enough validity checking to make sure we don't reference
206 		 * data outside the page passed to us. The page could be corrupt in
207 		 * many other ways, but at least we won't crash.
208 		 */
209 		if (ItemIdHasStorage(id) &&
210 			lp_len >= MinHeapTupleSize &&
211 			lp_offset == MAXALIGN(lp_offset) &&
212 			lp_offset + lp_len <= raw_page_size)
213 		{
214 			HeapTupleHeader tuphdr;
215 			bytea	   *tuple_data_bytea;
216 			int			tuple_data_len;
217 
218 			/* Extract information from the tuple header */
219 
220 			tuphdr = (HeapTupleHeader) PageGetItem(page, id);
221 
222 			values[4] = UInt32GetDatum(HeapTupleHeaderGetRawXmin(tuphdr));
223 			values[5] = UInt32GetDatum(HeapTupleHeaderGetRawXmax(tuphdr));
224 			/* shared with xvac */
225 			values[6] = UInt32GetDatum(HeapTupleHeaderGetRawCommandId(tuphdr));
226 			values[7] = PointerGetDatum(&tuphdr->t_ctid);
227 			values[8] = UInt32GetDatum(tuphdr->t_infomask2);
228 			values[9] = UInt32GetDatum(tuphdr->t_infomask);
229 			values[10] = UInt8GetDatum(tuphdr->t_hoff);
230 
231 			/* Copy raw tuple data into bytea attribute */
232 			tuple_data_len = lp_len - tuphdr->t_hoff;
233 			tuple_data_bytea = (bytea *) palloc(tuple_data_len + VARHDRSZ);
234 			SET_VARSIZE(tuple_data_bytea, tuple_data_len + VARHDRSZ);
235 			memcpy(VARDATA(tuple_data_bytea), (char *) tuphdr + tuphdr->t_hoff,
236 				   tuple_data_len);
237 			values[13] = PointerGetDatum(tuple_data_bytea);
238 
239 			/*
240 			 * We already checked that the item is completely within the raw
241 			 * page passed to us, with the length given in the line pointer.
242 			 * Let's check that t_hoff doesn't point over lp_len, before using
243 			 * it to access t_bits and oid.
244 			 */
245 			if (tuphdr->t_hoff >= SizeofHeapTupleHeader &&
246 				tuphdr->t_hoff <= lp_len &&
247 				tuphdr->t_hoff == MAXALIGN(tuphdr->t_hoff))
248 			{
249 				if (tuphdr->t_infomask & HEAP_HASNULL)
250 				{
251 					int			bits_len;
252 
253 					bits_len =
254 						BITMAPLEN(HeapTupleHeaderGetNatts(tuphdr)) * BITS_PER_BYTE;
255 					values[11] = CStringGetTextDatum(bits_to_text(tuphdr->t_bits, bits_len));
256 				}
257 				else
258 					nulls[11] = true;
259 
260 				if (tuphdr->t_infomask & HEAP_HASOID_OLD)
261 					values[12] = HeapTupleHeaderGetOidOld(tuphdr);
262 				else
263 					nulls[12] = true;
264 			}
265 			else
266 			{
267 				nulls[11] = true;
268 				nulls[12] = true;
269 			}
270 		}
271 		else
272 		{
273 			/*
274 			 * The line pointer is not used, or it's invalid. Set the rest of
275 			 * the fields to NULL
276 			 */
277 			int			i;
278 
279 			for (i = 4; i <= 13; i++)
280 				nulls[i] = true;
281 		}
282 
283 		/* Build and return the result tuple. */
284 		resultTuple = heap_form_tuple(inter_call_data->tupd, values, nulls);
285 		result = HeapTupleGetDatum(resultTuple);
286 
287 		inter_call_data->offset++;
288 
289 		SRF_RETURN_NEXT(fctx, result);
290 	}
291 	else
292 		SRF_RETURN_DONE(fctx);
293 }
294 
295 /*
296  * tuple_data_split_internal
297  *
298  * Split raw tuple data taken directly from a page into an array of bytea
299  * elements. This routine does a lookup on NULL values and creates array
300  * elements accordingly. This is a reimplementation of nocachegetattr()
301  * in heaptuple.c simplified for educational purposes.
302  */
303 static Datum
tuple_data_split_internal(Oid relid,char * tupdata,uint16 tupdata_len,uint16 t_infomask,uint16 t_infomask2,bits8 * t_bits,bool do_detoast)304 tuple_data_split_internal(Oid relid, char *tupdata,
305 						  uint16 tupdata_len, uint16 t_infomask,
306 						  uint16 t_infomask2, bits8 *t_bits,
307 						  bool do_detoast)
308 {
309 	ArrayBuildState *raw_attrs;
310 	int			nattrs;
311 	int			i;
312 	int			off = 0;
313 	Relation	rel;
314 	TupleDesc	tupdesc;
315 
316 	/* Get tuple descriptor from relation OID */
317 	rel = relation_open(relid, AccessShareLock);
318 	tupdesc = RelationGetDescr(rel);
319 
320 	raw_attrs = initArrayResult(BYTEAOID, CurrentMemoryContext, false);
321 	nattrs = tupdesc->natts;
322 
323 	if (rel->rd_rel->relam != HEAP_TABLE_AM_OID)
324 		ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
325 						errmsg("only heap AM is supported")));
326 
327 	if (nattrs < (t_infomask2 & HEAP_NATTS_MASK))
328 		ereport(ERROR,
329 				(errcode(ERRCODE_DATA_CORRUPTED),
330 				 errmsg("number of attributes in tuple header is greater than number of attributes in tuple descriptor")));
331 
332 	for (i = 0; i < nattrs; i++)
333 	{
334 		Form_pg_attribute attr;
335 		bool		is_null;
336 		bytea	   *attr_data = NULL;
337 
338 		attr = TupleDescAttr(tupdesc, i);
339 
340 		/*
341 		 * Tuple header can specify fewer attributes than tuple descriptor as
342 		 * ALTER TABLE ADD COLUMN without DEFAULT keyword does not actually
343 		 * change tuples in pages, so attributes with numbers greater than
344 		 * (t_infomask2 & HEAP_NATTS_MASK) should be treated as NULL.
345 		 */
346 		if (i >= (t_infomask2 & HEAP_NATTS_MASK))
347 			is_null = true;
348 		else
349 			is_null = (t_infomask & HEAP_HASNULL) && att_isnull(i, t_bits);
350 
351 		if (!is_null)
352 		{
353 			int			len;
354 
355 			if (attr->attlen == -1)
356 			{
357 				off = att_align_pointer(off, attr->attalign, -1,
358 										tupdata + off);
359 
360 				/*
361 				 * As VARSIZE_ANY throws an exception if it can't properly
362 				 * detect the type of external storage in macros VARTAG_SIZE,
363 				 * this check is repeated to have a nicer error handling.
364 				 */
365 				if (VARATT_IS_EXTERNAL(tupdata + off) &&
366 					!VARATT_IS_EXTERNAL_ONDISK(tupdata + off) &&
367 					!VARATT_IS_EXTERNAL_INDIRECT(tupdata + off))
368 					ereport(ERROR,
369 							(errcode(ERRCODE_DATA_CORRUPTED),
370 							 errmsg("first byte of varlena attribute is incorrect for attribute %d", i)));
371 
372 				len = VARSIZE_ANY(tupdata + off);
373 			}
374 			else
375 			{
376 				off = att_align_nominal(off, attr->attalign);
377 				len = attr->attlen;
378 			}
379 
380 			if (tupdata_len < off + len)
381 				ereport(ERROR,
382 						(errcode(ERRCODE_DATA_CORRUPTED),
383 						 errmsg("unexpected end of tuple data")));
384 
385 			if (attr->attlen == -1 && do_detoast)
386 				attr_data = DatumGetByteaPCopy(tupdata + off);
387 			else
388 			{
389 				attr_data = (bytea *) palloc(len + VARHDRSZ);
390 				SET_VARSIZE(attr_data, len + VARHDRSZ);
391 				memcpy(VARDATA(attr_data), tupdata + off, len);
392 			}
393 
394 			off = att_addlength_pointer(off, attr->attlen,
395 										tupdata + off);
396 		}
397 
398 		raw_attrs = accumArrayResult(raw_attrs, PointerGetDatum(attr_data),
399 									 is_null, BYTEAOID, CurrentMemoryContext);
400 		if (attr_data)
401 			pfree(attr_data);
402 	}
403 
404 	if (tupdata_len != off)
405 		ereport(ERROR,
406 				(errcode(ERRCODE_DATA_CORRUPTED),
407 				 errmsg("end of tuple reached without looking at all its data")));
408 
409 	relation_close(rel, AccessShareLock);
410 
411 	return makeArrayResult(raw_attrs, CurrentMemoryContext);
412 }
413 
414 /*
415  * tuple_data_split
416  *
417  * Split raw tuple data taken directly from page into distinct elements
418  * taking into account null values.
419  */
420 PG_FUNCTION_INFO_V1(tuple_data_split);
421 
422 Datum
tuple_data_split(PG_FUNCTION_ARGS)423 tuple_data_split(PG_FUNCTION_ARGS)
424 {
425 	Oid			relid;
426 	bytea	   *raw_data;
427 	uint16		t_infomask;
428 	uint16		t_infomask2;
429 	char	   *t_bits_str;
430 	bool		do_detoast = false;
431 	bits8	   *t_bits = NULL;
432 	Datum		res;
433 
434 	relid = PG_GETARG_OID(0);
435 	raw_data = PG_ARGISNULL(1) ? NULL : PG_GETARG_BYTEA_P(1);
436 	t_infomask = PG_GETARG_INT16(2);
437 	t_infomask2 = PG_GETARG_INT16(3);
438 	t_bits_str = PG_ARGISNULL(4) ? NULL :
439 		text_to_cstring(PG_GETARG_TEXT_PP(4));
440 
441 	if (PG_NARGS() >= 6)
442 		do_detoast = PG_GETARG_BOOL(5);
443 
444 	if (!superuser())
445 		ereport(ERROR,
446 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
447 				 errmsg("must be superuser to use raw page functions")));
448 
449 	if (!raw_data)
450 		PG_RETURN_NULL();
451 
452 	/*
453 	 * Convert t_bits string back to the bits8 array as represented in the
454 	 * tuple header.
455 	 */
456 	if (t_infomask & HEAP_HASNULL)
457 	{
458 		int			bits_str_len;
459 		int			bits_len;
460 
461 		bits_len = BITMAPLEN(t_infomask2 & HEAP_NATTS_MASK) * BITS_PER_BYTE;
462 		if (!t_bits_str)
463 			ereport(ERROR,
464 					(errcode(ERRCODE_DATA_CORRUPTED),
465 					 errmsg("t_bits string must not be NULL")));
466 
467 		bits_str_len = strlen(t_bits_str);
468 		if (bits_len != bits_str_len)
469 			ereport(ERROR,
470 					(errcode(ERRCODE_DATA_CORRUPTED),
471 					 errmsg("unexpected length of t_bits string: %u, expected %u",
472 							bits_str_len, bits_len)));
473 
474 		/* do the conversion */
475 		t_bits = text_to_bits(t_bits_str, bits_str_len);
476 	}
477 	else
478 	{
479 		if (t_bits_str)
480 			ereport(ERROR,
481 					(errcode(ERRCODE_DATA_CORRUPTED),
482 					 errmsg("t_bits string is expected to be NULL, but instead it is %zu bytes long",
483 							strlen(t_bits_str))));
484 	}
485 
486 	/* Split tuple data */
487 	res = tuple_data_split_internal(relid, (char *) raw_data + VARHDRSZ,
488 									VARSIZE(raw_data) - VARHDRSZ,
489 									t_infomask, t_infomask2, t_bits,
490 									do_detoast);
491 
492 	if (t_bits)
493 		pfree(t_bits);
494 
495 	PG_RETURN_ARRAYTYPE_P(res);
496 }
497 
498 /*
499  * heap_tuple_infomask_flags
500  *
501  * Decode into a human-readable format t_infomask and t_infomask2 associated
502  * to a tuple.  All the flags are described in access/htup_details.h.
503  */
504 PG_FUNCTION_INFO_V1(heap_tuple_infomask_flags);
505 
506 Datum
heap_tuple_infomask_flags(PG_FUNCTION_ARGS)507 heap_tuple_infomask_flags(PG_FUNCTION_ARGS)
508 {
509 #define HEAP_TUPLE_INFOMASK_COLS 2
510 	Datum		values[HEAP_TUPLE_INFOMASK_COLS];
511 	bool		nulls[HEAP_TUPLE_INFOMASK_COLS];
512 	uint16		t_infomask = PG_GETARG_INT16(0);
513 	uint16		t_infomask2 = PG_GETARG_INT16(1);
514 	int			cnt = 0;
515 	ArrayType  *a;
516 	int			bitcnt;
517 	Datum	   *flags;
518 	TupleDesc	tupdesc;
519 	HeapTuple	tuple;
520 
521 	if (!superuser())
522 		ereport(ERROR,
523 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
524 				 errmsg("must be superuser to use raw page functions")));
525 
526 	/* Build a tuple descriptor for our result type */
527 	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
528 		elog(ERROR, "return type must be a row type");
529 
530 	bitcnt = pg_popcount((const char *) &t_infomask, sizeof(uint16)) +
531 		pg_popcount((const char *) &t_infomask2, sizeof(uint16));
532 
533 	/* Initialize values and NULL flags arrays */
534 	MemSet(values, 0, sizeof(values));
535 	MemSet(nulls, 0, sizeof(nulls));
536 
537 	/* If no flags, return a set of empty arrays */
538 	if (bitcnt <= 0)
539 	{
540 		values[0] = PointerGetDatum(construct_empty_array(TEXTOID));
541 		values[1] = PointerGetDatum(construct_empty_array(TEXTOID));
542 		tuple = heap_form_tuple(tupdesc, values, nulls);
543 		PG_RETURN_DATUM(HeapTupleGetDatum(tuple));
544 	}
545 
546 	/* build set of raw flags */
547 	flags = (Datum *) palloc0(sizeof(Datum) * bitcnt);
548 
549 	/* decode t_infomask */
550 	if ((t_infomask & HEAP_HASNULL) != 0)
551 		flags[cnt++] = CStringGetTextDatum("HEAP_HASNULL");
552 	if ((t_infomask & HEAP_HASVARWIDTH) != 0)
553 		flags[cnt++] = CStringGetTextDatum("HEAP_HASVARWIDTH");
554 	if ((t_infomask & HEAP_HASEXTERNAL) != 0)
555 		flags[cnt++] = CStringGetTextDatum("HEAP_HASEXTERNAL");
556 	if ((t_infomask & HEAP_HASOID_OLD) != 0)
557 		flags[cnt++] = CStringGetTextDatum("HEAP_HASOID_OLD");
558 	if ((t_infomask & HEAP_XMAX_KEYSHR_LOCK) != 0)
559 		flags[cnt++] = CStringGetTextDatum("HEAP_XMAX_KEYSHR_LOCK");
560 	if ((t_infomask & HEAP_COMBOCID) != 0)
561 		flags[cnt++] = CStringGetTextDatum("HEAP_COMBOCID");
562 	if ((t_infomask & HEAP_XMAX_EXCL_LOCK) != 0)
563 		flags[cnt++] = CStringGetTextDatum("HEAP_XMAX_EXCL_LOCK");
564 	if ((t_infomask & HEAP_XMAX_LOCK_ONLY) != 0)
565 		flags[cnt++] = CStringGetTextDatum("HEAP_XMAX_LOCK_ONLY");
566 	if ((t_infomask & HEAP_XMIN_COMMITTED) != 0)
567 		flags[cnt++] = CStringGetTextDatum("HEAP_XMIN_COMMITTED");
568 	if ((t_infomask & HEAP_XMIN_INVALID) != 0)
569 		flags[cnt++] = CStringGetTextDatum("HEAP_XMIN_INVALID");
570 	if ((t_infomask & HEAP_XMAX_COMMITTED) != 0)
571 		flags[cnt++] = CStringGetTextDatum("HEAP_XMAX_COMMITTED");
572 	if ((t_infomask & HEAP_XMAX_INVALID) != 0)
573 		flags[cnt++] = CStringGetTextDatum("HEAP_XMAX_INVALID");
574 	if ((t_infomask & HEAP_XMAX_IS_MULTI) != 0)
575 		flags[cnt++] = CStringGetTextDatum("HEAP_XMAX_IS_MULTI");
576 	if ((t_infomask & HEAP_UPDATED) != 0)
577 		flags[cnt++] = CStringGetTextDatum("HEAP_UPDATED");
578 	if ((t_infomask & HEAP_MOVED_OFF) != 0)
579 		flags[cnt++] = CStringGetTextDatum("HEAP_MOVED_OFF");
580 	if ((t_infomask & HEAP_MOVED_IN) != 0)
581 		flags[cnt++] = CStringGetTextDatum("HEAP_MOVED_IN");
582 
583 	/* decode t_infomask2 */
584 	if ((t_infomask2 & HEAP_KEYS_UPDATED) != 0)
585 		flags[cnt++] = CStringGetTextDatum("HEAP_KEYS_UPDATED");
586 	if ((t_infomask2 & HEAP_HOT_UPDATED) != 0)
587 		flags[cnt++] = CStringGetTextDatum("HEAP_HOT_UPDATED");
588 	if ((t_infomask2 & HEAP_ONLY_TUPLE) != 0)
589 		flags[cnt++] = CStringGetTextDatum("HEAP_ONLY_TUPLE");
590 
591 	/* build value */
592 	Assert(cnt <= bitcnt);
593 	a = construct_array(flags, cnt, TEXTOID, -1, false, TYPALIGN_INT);
594 	values[0] = PointerGetDatum(a);
595 
596 	/*
597 	 * Build set of combined flags.  Use the same array as previously, this
598 	 * keeps the code simple.
599 	 */
600 	cnt = 0;
601 	MemSet(flags, 0, sizeof(Datum) * bitcnt);
602 
603 	/* decode combined masks of t_infomask */
604 	if ((t_infomask & HEAP_XMAX_SHR_LOCK) == HEAP_XMAX_SHR_LOCK)
605 		flags[cnt++] = CStringGetTextDatum("HEAP_XMAX_SHR_LOCK");
606 	if ((t_infomask & HEAP_XMIN_FROZEN) == HEAP_XMIN_FROZEN)
607 		flags[cnt++] = CStringGetTextDatum("HEAP_XMIN_FROZEN");
608 	if ((t_infomask & HEAP_MOVED) == HEAP_MOVED)
609 		flags[cnt++] = CStringGetTextDatum("HEAP_MOVED");
610 
611 	/* Build an empty array if there are no combined flags */
612 	if (cnt == 0)
613 		a = construct_empty_array(TEXTOID);
614 	else
615 		a = construct_array(flags, cnt, TEXTOID, -1, false, TYPALIGN_INT);
616 	pfree(flags);
617 	values[1] = PointerGetDatum(a);
618 
619 	/* Returns the record as Datum */
620 	tuple = heap_form_tuple(tupdesc, values, nulls);
621 	PG_RETURN_DATUM(HeapTupleGetDatum(tuple));
622 }
623