Adding upstream version 14.5.upstream/14.5upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 793 insertions, 0 deletions

diff --git a/contrib/pageinspect/btreefuncs.c b/contrib/pageinspect/btreefuncs.c
new file mode 100644
index 0000000..2044b88
--- /dev/null
+++ b/contrib/pageinspect/btreefuncs.c
@@ -0,0 +1,793 @@
+/*
+ * contrib/pageinspect/btreefuncs.c
+ *
+ *
+ * btreefuncs.c
+ *
+ * Copyright (c) 2006 Satoshi Nagayasu <nagayasus@nttdata.co.jp>
+ *
+ * Permission to use, copy, modify, and distribute this software and
+ * its documentation for any purpose, without fee, and without a
+ * written agreement is hereby granted, provided that the above
+ * copyright notice and this paragraph and the following two
+ * paragraphs appear in all copies.
+ *
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE TO ANY PARTY FOR DIRECT,
+ * INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
+ * LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
+ * DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * THE AUTHOR SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS
+ * IS" BASIS, AND THE AUTHOR HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE,
+ * SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ */
+
+#include "postgres.h"
+
+#include "access/nbtree.h"
+#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"
+
+PG_FUNCTION_INFO_V1(bt_metap);
+PG_FUNCTION_INFO_V1(bt_page_items_1_9);
+PG_FUNCTION_INFO_V1(bt_page_items);
+PG_FUNCTION_INFO_V1(bt_page_items_bytea);
+PG_FUNCTION_INFO_V1(bt_page_stats_1_9);
+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) { \
+		if ( RelationGetNumberOfBlocks(rel) <= (BlockNumber) (blkno) ) \
+			 elog(ERROR, "block number out of range"); }
+
+/* ------------------------------------------------
+ * structure for single btree page statistics
+ * ------------------------------------------------
+ */
+typedef struct BTPageStat
+{
+	uint32		blkno;
+	uint32		live_items;
+	uint32		dead_items;
+	uint32		page_size;
+	uint32		max_avail;
+	uint32		free_size;
+	uint32		avg_item_size;
+	char		type;
+
+	/* opaque data */
+	BlockNumber btpo_prev;
+	BlockNumber btpo_next;
+	uint32		btpo_level;
+	uint16		btpo_flags;
+	BTCycleId	btpo_cycleid;
+} BTPageStat;
+
+
+/* -------------------------------------------------
+ * GetBTPageStatistics()
+ *
+ * Collect statistics of single b-tree page
+ * -------------------------------------------------
+ */
+static void
+GetBTPageStatistics(BlockNumber blkno, Buffer buffer, BTPageStat *stat)
+{
+	Page		page = BufferGetPage(buffer);
+	PageHeader	phdr = (PageHeader) page;
+	OffsetNumber maxoff = PageGetMaxOffsetNumber(page);
+	BTPageOpaque opaque = (BTPageOpaque) PageGetSpecialPointer(page);
+	int			item_size = 0;
+	int			off;
+
+	stat->blkno = blkno;
+
+	stat->max_avail = BLCKSZ - (BLCKSZ - phdr->pd_special + SizeOfPageHeaderData);
+
+	stat->dead_items = stat->live_items = 0;
+
+	stat->page_size = PageGetPageSize(page);
+
+	/* page type (flags) */
+	if (P_ISDELETED(opaque))
+	{
+		/* We divide deleted pages into leaf ('d') or internal ('D') */
+		if (P_ISLEAF(opaque) || !P_HAS_FULLXID(opaque))
+			stat->type = 'd';
+		else
+			stat->type = 'D';
+
+		/*
+		 * Report safexid in a deleted page.
+		 *
+		 * Handle pg_upgrade'd deleted pages that used the previous safexid
+		 * representation in btpo_level field (this used to be a union type
+		 * called "bpto").
+		 */
+		if (P_HAS_FULLXID(opaque))
+		{
+			FullTransactionId safexid = BTPageGetDeleteXid(page);
+
+			elog(DEBUG2, "deleted page from block %u has safexid %u:%u",
+				 blkno, EpochFromFullTransactionId(safexid),
+				 XidFromFullTransactionId(safexid));
+		}
+		else
+			elog(DEBUG2, "deleted page from block %u has safexid %u",
+				 blkno, opaque->btpo_level);
+
+		/* Don't interpret BTDeletedPageData as index tuples */
+		maxoff = InvalidOffsetNumber;
+	}
+	else if (P_IGNORE(opaque))
+		stat->type = 'e';
+	else if (P_ISLEAF(opaque))
+		stat->type = 'l';
+	else if (P_ISROOT(opaque))
+		stat->type = 'r';
+	else
+		stat->type = 'i';
+
+	/* btpage opaque data */
+	stat->btpo_prev = opaque->btpo_prev;
+	stat->btpo_next = opaque->btpo_next;
+	stat->btpo_level = opaque->btpo_level;
+	stat->btpo_flags = opaque->btpo_flags;
+	stat->btpo_cycleid = opaque->btpo_cycleid;
+
+	/* count live and dead tuples, and free space */
+	for (off = FirstOffsetNumber; off <= maxoff; off++)
+	{
+		IndexTuple	itup;
+
+		ItemId		id = PageGetItemId(page, off);
+
+		itup = (IndexTuple) PageGetItem(page, id);
+
+		item_size += IndexTupleSize(itup);
+
+		if (!ItemIdIsDead(id))
+			stat->live_items++;
+		else
+			stat->dead_items++;
+	}
+	stat->free_size = PageGetFreeSpace(page);
+
+	if ((stat->live_items + stat->dead_items) > 0)
+		stat->avg_item_size = item_size / (stat->live_items + stat->dead_items);
+	else
+		stat->avg_item_size = 0;
+}
+
+/* -----------------------------------------------
+ * bt_page_stats()
+ *
+ * Usage: SELECT * FROM bt_page_stats('t1_pkey', 1);
+ * -----------------------------------------------
+ */
+static Datum
+bt_page_stats_internal(PG_FUNCTION_ARGS, enum pageinspect_version ext_version)
+{
+	text	   *relname = PG_GETARG_TEXT_PP(0);
+	int64		blkno = (ext_version == PAGEINSPECT_V1_8 ? PG_GETARG_UINT32(1) : PG_GETARG_INT64(1));
+	Buffer		buffer;
+	Relation	rel;
+	RangeVar   *relrv;
+	Datum		result;
+	HeapTuple	tuple;
+	TupleDesc	tupleDesc;
+	int			j;
+	char	   *values[11];
+	BTPageStat	stat;
+
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("must be superuser to use pageinspect functions")));
+
+	relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
+	rel = relation_openrv(relrv, AccessShareLock);
+
+	if (!IS_INDEX(rel) || !IS_BTREE(rel))
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("\"%s\" is not a %s index",
+						RelationGetRelationName(rel), "btree")));
+
+	/*
+	 * Reject attempts to read non-local temporary relations; we would be
+	 * likely to get wrong data since we have no visibility into the owning
+	 * session's local buffers.
+	 */
+	if (RELATION_IS_OTHER_TEMP(rel))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot access temporary tables of other sessions")));
+
+	if (blkno < 0 || blkno > MaxBlockNumber)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid block number")));
+
+	if (blkno == 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("block 0 is a meta page")));
+
+	CHECK_RELATION_BLOCK_RANGE(rel, blkno);
+
+	buffer = ReadBuffer(rel, blkno);
+	LockBuffer(buffer, BUFFER_LOCK_SHARE);
+
+	/* keep compiler quiet */
+	stat.btpo_prev = stat.btpo_next = InvalidBlockNumber;
+	stat.btpo_flags = stat.free_size = stat.avg_item_size = 0;
+
+	GetBTPageStatistics(blkno, buffer, &stat);
+
+	UnlockReleaseBuffer(buffer);
+	relation_close(rel, AccessShareLock);
+
+	/* 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");
+
+	j = 0;
+	values[j++] = psprintf("%u", stat.blkno);
+	values[j++] = psprintf("%c", stat.type);
+	values[j++] = psprintf("%u", stat.live_items);
+	values[j++] = psprintf("%u", stat.dead_items);
+	values[j++] = psprintf("%u", stat.avg_item_size);
+	values[j++] = psprintf("%u", stat.page_size);
+	values[j++] = psprintf("%u", stat.free_size);
+	values[j++] = psprintf("%u", stat.btpo_prev);
+	values[j++] = psprintf("%u", stat.btpo_next);
+	values[j++] = psprintf("%u", stat.btpo_level);
+	values[j++] = psprintf("%d", stat.btpo_flags);
+
+	tuple = BuildTupleFromCStrings(TupleDescGetAttInMetadata(tupleDesc),
+								   values);
+
+	result = HeapTupleGetDatum(tuple);
+
+	PG_RETURN_DATUM(result);
+}
+
+Datum
+bt_page_stats_1_9(PG_FUNCTION_ARGS)
+{
+	return bt_page_stats_internal(fcinfo, PAGEINSPECT_V1_9);
+}
+
+/* entry point for old extension version */
+Datum
+bt_page_stats(PG_FUNCTION_ARGS)
+{
+	return bt_page_stats_internal(fcinfo, PAGEINSPECT_V1_8);
+}
+
+
+/*
+ * cross-call data structure for SRF
+ */
+struct user_args
+{
+	Page		page;
+	OffsetNumber offset;
+	bool		leafpage;
+	bool		rightmost;
+	TupleDesc	tupd;
+};
+
+/*-------------------------------------------------------
+ * bt_page_print_tuples()
+ *
+ * Form a tuple describing index tuple at a given offset
+ * ------------------------------------------------------
+ */
+static Datum
+bt_page_print_tuples(struct user_args *uargs)
+{
+	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,
+			   *datacstring;
+	char	   *ptr;
+	ItemPointer htid;
+
+	id = PageGetItemId(page, offset);
+
+	if (!ItemIdIsValid(id))
+		elog(ERROR, "invalid ItemId");
+
+	itup = (IndexTuple) PageGetItem(page, id);
+
+	j = 0;
+	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);
+	datacstring = dump;
+	for (off = 0; off < dlen; off++)
+	{
+		if (off > 0)
+			*dump++ = ' ';
+		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, TYPALIGN_SHORT));
+		pfree(tids_datum);
+	}
+	else
+		nulls[j++] = true;
+
+	/* Build and return the result tuple */
+	tuple = heap_form_tuple(uargs->tupd, values, nulls);
+
+	return HeapTupleGetDatum(tuple);
+}
+
+/*-------------------------------------------------------
+ * bt_page_items()
+ *
+ * Get IndexTupleData set in a btree page
+ *
+ * Usage: SELECT * FROM bt_page_items('t1_pkey', 1);
+ *-------------------------------------------------------
+ */
+static Datum
+bt_page_items_internal(PG_FUNCTION_ARGS, enum pageinspect_version ext_version)
+{
+	text	   *relname = PG_GETARG_TEXT_PP(0);
+	int64		blkno = (ext_version == PAGEINSPECT_V1_8 ? PG_GETARG_UINT32(1) : PG_GETARG_INT64(1));
+	Datum		result;
+	FuncCallContext *fctx;
+	MemoryContext mctx;
+	struct user_args *uargs;
+
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("must be superuser to use pageinspect functions")));
+
+	if (SRF_IS_FIRSTCALL())
+	{
+		RangeVar   *relrv;
+		Relation	rel;
+		Buffer		buffer;
+		BTPageOpaque opaque;
+		TupleDesc	tupleDesc;
+
+		fctx = SRF_FIRSTCALL_INIT();
+
+		relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
+		rel = relation_openrv(relrv, AccessShareLock);
+
+		if (!IS_INDEX(rel) || !IS_BTREE(rel))
+			ereport(ERROR,
+					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+					 errmsg("\"%s\" is not a %s index",
+							RelationGetRelationName(rel), "btree")));
+
+		/*
+		 * Reject attempts to read non-local temporary relations; we would be
+		 * likely to get wrong data since we have no visibility into the
+		 * owning session's local buffers.
+		 */
+		if (RELATION_IS_OTHER_TEMP(rel))
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("cannot access temporary tables of other sessions")));
+
+		if (blkno < 0 || blkno > MaxBlockNumber)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("invalid block number")));
+
+		if (blkno == 0)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("block 0 is a meta page")));
+
+		CHECK_RELATION_BLOCK_RANGE(rel, blkno);
+
+		buffer = ReadBuffer(rel, blkno);
+		LockBuffer(buffer, BUFFER_LOCK_SHARE);
+
+		/*
+		 * We copy the page into local storage to avoid holding pin on the
+		 * buffer longer than we must, and possibly failing to release it at
+		 * all if the calling query doesn't fetch all rows.
+		 */
+		mctx = MemoryContextSwitchTo(fctx->multi_call_memory_ctx);
+
+		uargs = palloc(sizeof(struct user_args));
+
+		uargs->page = palloc(BLCKSZ);
+		memcpy(uargs->page, BufferGetPage(buffer), BLCKSZ);
+
+		UnlockReleaseBuffer(buffer);
+		relation_close(rel, AccessShareLock);
+
+		uargs->offset = FirstOffsetNumber;
+
+		opaque = (BTPageOpaque) PageGetSpecialPointer(uargs->page);
+
+		if (!P_ISDELETED(opaque))
+			fctx->max_calls = PageGetMaxOffsetNumber(uargs->page);
+		else
+		{
+			/* Don't interpret BTDeletedPageData as index tuples */
+			elog(NOTICE, "page from block " INT64_FORMAT " is deleted", blkno);
+			fctx->max_calls = 0;
+		}
+		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);
+
+		uargs->tupd = tupleDesc;
+
+		fctx->user_fctx = uargs;
+
+		MemoryContextSwitchTo(mctx);
+	}
+
+	fctx = SRF_PERCALL_SETUP();
+	uargs = fctx->user_fctx;
+
+	if (fctx->call_cntr < fctx->max_calls)
+	{
+		result = bt_page_print_tuples(uargs);
+		uargs->offset++;
+		SRF_RETURN_NEXT(fctx, result);
+	}
+
+	SRF_RETURN_DONE(fctx);
+}
+
+Datum
+bt_page_items_1_9(PG_FUNCTION_ARGS)
+{
+	return bt_page_items_internal(fcinfo, PAGEINSPECT_V1_9);
+}
+
+/* entry point for old extension version */
+Datum
+bt_page_items(PG_FUNCTION_ARGS)
+{
+	return bt_page_items_internal(fcinfo, PAGEINSPECT_V1_8);
+}
+
+/*-------------------------------------------------------
+ * bt_page_items_bytea()
+ *
+ * Get IndexTupleData set in a btree page
+ *
+ * Usage: SELECT * FROM bt_page_items(get_raw_page('t1_pkey', 1));
+ *-------------------------------------------------------
+ */
+
+Datum
+bt_page_items_bytea(PG_FUNCTION_ARGS)
+{
+	bytea	   *raw_page = PG_GETARG_BYTEA_P(0);
+	Datum		result;
+	FuncCallContext *fctx;
+	struct user_args *uargs;
+
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("must be superuser to use raw page functions")));
+
+	if (SRF_IS_FIRSTCALL())
+	{
+		BTPageOpaque opaque;
+		MemoryContext mctx;
+		TupleDesc	tupleDesc;
+
+		fctx = SRF_FIRSTCALL_INIT();
+		mctx = MemoryContextSwitchTo(fctx->multi_call_memory_ctx);
+
+		uargs = palloc(sizeof(struct user_args));
+
+		uargs->page = get_page_from_raw(raw_page);
+
+		if (PageIsNew(uargs->page))
+		{
+			MemoryContextSwitchTo(mctx);
+			PG_RETURN_NULL();
+		}
+
+		uargs->offset = FirstOffsetNumber;
+
+		/* verify the special space has the expected size */
+		if (PageGetSpecialSize(uargs->page) != MAXALIGN(sizeof(BTPageOpaqueData)))
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("input page is not a valid %s page", "btree"),
+					 errdetail("Expected special size %d, got %d.",
+							   (int) MAXALIGN(sizeof(BTPageOpaqueData)),
+							   (int) PageGetSpecialSize(uargs->page))));
+
+		opaque = (BTPageOpaque) PageGetSpecialPointer(uargs->page);
+
+		if (P_ISMETA(opaque))
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("block is a meta page")));
+
+		if (P_ISLEAF(opaque) && opaque->btpo_level != 0)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("block is not a valid btree leaf page")));
+
+		if (P_ISDELETED(opaque))
+			elog(NOTICE, "page is deleted");
+
+		if (!P_ISDELETED(opaque))
+			fctx->max_calls = PageGetMaxOffsetNumber(uargs->page);
+		else
+		{
+			/* Don't interpret BTDeletedPageData as index tuples */
+			elog(NOTICE, "page from block is deleted");
+			fctx->max_calls = 0;
+		}
+		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);
+
+		uargs->tupd = tupleDesc;
+
+		fctx->user_fctx = uargs;
+
+		MemoryContextSwitchTo(mctx);
+	}
+
+	fctx = SRF_PERCALL_SETUP();
+	uargs = fctx->user_fctx;
+
+	if (fctx->call_cntr < fctx->max_calls)
+	{
+		result = bt_page_print_tuples(uargs);
+		uargs->offset++;
+		SRF_RETURN_NEXT(fctx, result);
+	}
+
+	SRF_RETURN_DONE(fctx);
+}
+
+/* Number of output arguments (columns) for bt_metap() */
+#define BT_METAP_COLS_V1_8		9
+
+/* ------------------------------------------------
+ * bt_metap()
+ *
+ * Get a btree's meta-page information
+ *
+ * Usage: SELECT * FROM bt_metap('t1_pkey')
+ * ------------------------------------------------
+ */
+Datum
+bt_metap(PG_FUNCTION_ARGS)
+{
+	text	   *relname = PG_GETARG_TEXT_PP(0);
+	Datum		result;
+	Relation	rel;
+	RangeVar   *relrv;
+	BTMetaPageData *metad;
+	TupleDesc	tupleDesc;
+	int			j;
+	char	   *values[9];
+	Buffer		buffer;
+	Page		page;
+	HeapTuple	tuple;
+
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("must be superuser to use pageinspect functions")));
+
+	relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
+	rel = relation_openrv(relrv, AccessShareLock);
+
+	if (!IS_INDEX(rel) || !IS_BTREE(rel))
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("\"%s\" is not a %s index",
+						RelationGetRelationName(rel), "btree")));
+
+	/*
+	 * Reject attempts to read non-local temporary relations; we would be
+	 * likely to get wrong data since we have no visibility into the owning
+	 * session's local buffers.
+	 */
+	if (RELATION_IS_OTHER_TEMP(rel))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot access temporary tables of other sessions")));
+
+	buffer = ReadBuffer(rel, 0);
+	LockBuffer(buffer, BUFFER_LOCK_SHARE);
+
+	page = BufferGetPage(buffer);
+	metad = BTPageGetMeta(page);
+
+	/* 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");
+
+	/*
+	 * We need a kluge here to detect API versions prior to 1.8.  Earlier
+	 * versions incorrectly used int4 for certain columns.
+	 *
+	 * There is no way to reliably avoid the problems created by the old
+	 * function definition at this point, so insist that the user update the
+	 * extension.
+	 */
+	if (tupleDesc->natts < BT_METAP_COLS_V1_8)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
+				 errmsg("function has wrong number of declared columns"),
+				 errhint("To resolve the problem, update the \"pageinspect\" extension to the latest version.")));
+
+	j = 0;
+	values[j++] = psprintf("%d", metad->btm_magic);
+	values[j++] = psprintf("%d", metad->btm_version);
+	values[j++] = psprintf(INT64_FORMAT, (int64) metad->btm_root);
+	values[j++] = psprintf(INT64_FORMAT, (int64) metad->btm_level);
+	values[j++] = psprintf(INT64_FORMAT, (int64) metad->btm_fastroot);
+	values[j++] = psprintf(INT64_FORMAT, (int64) metad->btm_fastlevel);
+
+	/*
+	 * Get values of extended metadata if available, use default values
+	 * 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(INT64_FORMAT,
+							   (int64) metad->btm_last_cleanup_num_delpages);
+		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),
+								   values);
+
+	result = HeapTupleGetDatum(tuple);
+
+	UnlockReleaseBuffer(buffer);
+	relation_close(rel, AccessShareLock);
+
+	PG_RETURN_DATUM(result);
+}