1 files changed, 350 insertions, 0 deletions
diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c
new file mode 100644
index 00000000000..5e5c7cce244
--- /dev/null
+++ b/contrib/pg_visibility/pg_visibility.c
@@ -0,0 +1,350 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_visibility.c
+ *	  display visibility map information and page-level visibility bits
+ *
+ *	  contrib/pg_visibility/pg_visibility.c
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/htup_details.h"
+#include "access/visibilitymap.h"
+#include "catalog/pg_type.h"
+#include "funcapi.h"
+#include "miscadmin.h"
+#include "storage/bufmgr.h"
+#include "utils/rel.h"
+
+PG_MODULE_MAGIC;
+
+typedef struct vbits
+{
+	BlockNumber	next;
+	BlockNumber	count;
+	uint8		bits[FLEXIBLE_ARRAY_MEMBER];
+} vbits;
+
+PG_FUNCTION_INFO_V1(pg_visibility_map);
+PG_FUNCTION_INFO_V1(pg_visibility_map_rel);
+PG_FUNCTION_INFO_V1(pg_visibility);
+PG_FUNCTION_INFO_V1(pg_visibility_rel);
+PG_FUNCTION_INFO_V1(pg_visibility_map_summary);
+
+static TupleDesc pg_visibility_tupdesc(bool include_blkno, bool include_pd);
+static vbits *collect_visibility_data(Oid relid, bool include_pd);
+
+/*
+ * Visibility map information for a single block of a relation.
+ */
+Datum
+pg_visibility_map(PG_FUNCTION_ARGS)
+{
+	Oid			relid = PG_GETARG_OID(0);
+	int64		blkno = PG_GETARG_INT64(1);
+	int32		mapbits;
+	Relation	rel;
+	Buffer		vmbuffer = InvalidBuffer;
+	TupleDesc	tupdesc;
+	Datum		values[2];
+	bool		nulls[2];
+
+	rel = relation_open(relid, AccessShareLock);
+
+	if (blkno < 0 || blkno > MaxBlockNumber)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid block number")));
+
+	tupdesc = pg_visibility_tupdesc(false, false);
+	MemSet(nulls, 0, sizeof(nulls));
+
+	mapbits = (int32) visibilitymap_get_status(rel, blkno, &vmbuffer);
+	if (vmbuffer != InvalidBuffer)
+		ReleaseBuffer(vmbuffer);
+	values[0] = BoolGetDatum((mapbits & VISIBILITYMAP_ALL_VISIBLE) != 0);
+	values[1] = BoolGetDatum((mapbits & VISIBILITYMAP_ALL_FROZEN) != 0);
+
+	relation_close(rel, AccessShareLock);
+
+	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
+/*
+ * Visibility map information for a single block of a relation, plus the
+ * page-level information for the same block.
+ */
+Datum
+pg_visibility(PG_FUNCTION_ARGS)
+{
+	Oid			relid = PG_GETARG_OID(0);
+	int64		blkno = PG_GETARG_INT64(1);
+	int32		mapbits;
+	Relation	rel;
+	Buffer		vmbuffer = InvalidBuffer;
+	Buffer		buffer;
+	Page		page;
+	TupleDesc	tupdesc;
+	Datum		values[3];
+	bool		nulls[3];
+
+	rel = relation_open(relid, AccessShareLock);
+
+	if (blkno < 0 || blkno > MaxBlockNumber)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid block number")));
+
+	tupdesc = pg_visibility_tupdesc(false, true);
+	MemSet(nulls, 0, sizeof(nulls));
+
+	mapbits = (int32) visibilitymap_get_status(rel, blkno, &vmbuffer);
+	if (vmbuffer != InvalidBuffer)
+		ReleaseBuffer(vmbuffer);
+	values[0] = BoolGetDatum((mapbits & VISIBILITYMAP_ALL_VISIBLE) != 0);
+	values[1] = BoolGetDatum((mapbits & VISIBILITYMAP_ALL_FROZEN) != 0);
+
+	buffer = ReadBuffer(rel, blkno);
+	LockBuffer(buffer, BUFFER_LOCK_SHARE);
+
+	page = BufferGetPage(buffer);
+	values[2] = BoolGetDatum(PageIsAllVisible(page));
+
+	UnlockReleaseBuffer(buffer);
+
+	relation_close(rel, AccessShareLock);
+
+	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
+/*
+ * Visibility map information for every block in a relation.
+ */
+Datum
+pg_visibility_map_rel(PG_FUNCTION_ARGS)
+{
+	FuncCallContext *funcctx;
+	vbits	   *info;
+
+	if (SRF_IS_FIRSTCALL())
+	{
+		Oid			relid = PG_GETARG_OID(0);
+		MemoryContext	oldcontext;
+
+		funcctx = SRF_FIRSTCALL_INIT();
+		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
+		funcctx->tuple_desc = pg_visibility_tupdesc(true, false);
+		funcctx->user_fctx = collect_visibility_data(relid, false);
+		MemoryContextSwitchTo(oldcontext);
+	}
+
+	funcctx = SRF_PERCALL_SETUP();
+	info = (vbits *) funcctx->user_fctx;
+
+	if (info->next < info->count)
+	{
+		Datum		values[3];
+		bool		nulls[3];
+		HeapTuple	tuple;
+
+		MemSet(nulls, 0, sizeof(nulls));
+		values[0] = Int64GetDatum(info->next);
+		values[1] = BoolGetDatum((info->bits[info->next] & (1 << 0)) != 0);
+		values[2] = BoolGetDatum((info->bits[info->next] & (1 << 1)) != 0);
+		info->next++;
+
+		tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
+		SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(tuple));
+	}
+
+	SRF_RETURN_DONE(funcctx);
+}
+
+/*
+ * Visibility map information for every block in a relation, plus the page
+ * level information for each block.
+ */
+Datum
+pg_visibility_rel(PG_FUNCTION_ARGS)
+{
+	FuncCallContext *funcctx;
+	vbits	   *info;
+
+	if (SRF_IS_FIRSTCALL())
+	{
+		Oid			relid = PG_GETARG_OID(0);
+		MemoryContext	oldcontext;
+
+		funcctx = SRF_FIRSTCALL_INIT();
+		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
+		funcctx->tuple_desc = pg_visibility_tupdesc(true, true);
+		funcctx->user_fctx = collect_visibility_data(relid, true);
+		MemoryContextSwitchTo(oldcontext);
+	}
+
+	funcctx = SRF_PERCALL_SETUP();
+	info = (vbits *) funcctx->user_fctx;
+
+	if (info->next < info->count)
+	{
+		Datum		values[4];
+		bool		nulls[4];
+		HeapTuple	tuple;
+
+		MemSet(nulls, 0, sizeof(nulls));
+		values[0] = Int64GetDatum(info->next);
+		values[1] = BoolGetDatum((info->bits[info->next] & (1 << 0)) != 0);
+		values[2] = BoolGetDatum((info->bits[info->next] & (1 << 1)) != 0);
+		values[3] = BoolGetDatum((info->bits[info->next] & (1 << 2)) != 0);
+		info->next++;
+
+		tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
+		SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(tuple));
+	}
+
+	SRF_RETURN_DONE(funcctx);
+}
+
+/*
+ * Count the number of all-visible and all-frozen pages in the visibility
+ * map for a particular relation.
+ */
+Datum
+pg_visibility_map_summary(PG_FUNCTION_ARGS)
+{
+	Oid			relid = PG_GETARG_OID(0);
+	Relation	rel;
+	BlockNumber	nblocks;
+	BlockNumber	blkno;
+	Buffer		vmbuffer = InvalidBuffer;
+	int64		all_visible = 0;
+	int64		all_frozen = 0;
+	TupleDesc	tupdesc;
+	Datum		values[2];
+	bool		nulls[2];
+
+	rel = relation_open(relid, AccessShareLock);
+	nblocks = RelationGetNumberOfBlocks(rel);
+
+	for (blkno = 0; blkno < nblocks; ++blkno)
+	{
+		int32		mapbits;
+
+		/* Make sure we are interruptible. */
+		CHECK_FOR_INTERRUPTS();
+
+		/* Get map info. */
+		mapbits = (int32) visibilitymap_get_status(rel, blkno, &vmbuffer);
+		if ((mapbits & VISIBILITYMAP_ALL_VISIBLE) != 0)
+			++all_visible;
+		if ((mapbits & VISIBILITYMAP_ALL_FROZEN) != 0)
+			++all_frozen;
+	}
+
+	/* Clean up. */
+	if (vmbuffer != InvalidBuffer)
+		ReleaseBuffer(vmbuffer);
+	relation_close(rel, AccessShareLock);
+
+	tupdesc = CreateTemplateTupleDesc(2, false);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "all_visible", INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "all_frozen", INT8OID, -1, 0);
+	tupdesc = BlessTupleDesc(tupdesc);
+
+	MemSet(nulls, 0, sizeof(nulls));
+	values[0] = Int64GetDatum(all_visible);
+	values[1] = Int64GetDatum(all_frozen);
+
+	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
+/*
+ * Helper function to construct whichever TupleDesc we need for a particular
+ * call.
+ */
+static TupleDesc
+pg_visibility_tupdesc(bool include_blkno, bool include_pd)
+{
+	TupleDesc	tupdesc;
+	AttrNumber	maxattr = 2;
+	AttrNumber	a = 0;
+
+	if (include_blkno)
+		++maxattr;
+	if (include_pd)
+		++maxattr;
+	tupdesc = CreateTemplateTupleDesc(maxattr, false);
+	if (include_blkno)
+		TupleDescInitEntry(tupdesc, ++a, "blkno", INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, ++a, "all_visible", BOOLOID, -1, 0);
+	TupleDescInitEntry(tupdesc, ++a, "all_frozen", BOOLOID, -1, 0);
+	if (include_pd)
+		TupleDescInitEntry(tupdesc, ++a, "pd_all_visible", BOOLOID, -1, 0);
+	Assert(a == maxattr);
+
+	return BlessTupleDesc(tupdesc);
+}
+
+/*
+ * Collect visibility data about a relation.
+ */
+static vbits *
+collect_visibility_data(Oid relid, bool include_pd)
+{
+	Relation	rel;
+	BlockNumber	nblocks;
+	vbits	   *info;
+	BlockNumber	blkno;
+	Buffer		vmbuffer = InvalidBuffer;
+	BufferAccessStrategy	bstrategy = GetAccessStrategy(BAS_BULKREAD);
+
+	rel = relation_open(relid, AccessShareLock);
+
+	nblocks = RelationGetNumberOfBlocks(rel);
+	info = palloc0(offsetof(vbits, bits) + nblocks);
+	info->next = 0;
+	info->count = nblocks;
+
+	for (blkno = 0; blkno < nblocks; ++blkno)
+	{
+		int32		mapbits;
+
+		/* Make sure we are interruptible. */
+		CHECK_FOR_INTERRUPTS();
+
+		/* Get map info. */
+		mapbits = (int32) visibilitymap_get_status(rel, blkno, &vmbuffer);
+		if ((mapbits & VISIBILITYMAP_ALL_VISIBLE) != 0)
+			info->bits[blkno] |= (1 << 0);
+		if ((mapbits & VISIBILITYMAP_ALL_FROZEN) != 0)
+			info->bits[blkno] |= (1 << 1);
+
+		/*
+		 * Page-level data requires reading every block, so only get it if
+		 * the caller needs it.  Use a buffer access strategy, too, to prevent
+		 * cache-trashing.
+		 */
+		if (include_pd)
+		{
+			Buffer		buffer;
+			Page		page;
+
+			buffer = ReadBufferExtended(rel, MAIN_FORKNUM, blkno, RBM_NORMAL,
+										bstrategy);
+			LockBuffer(buffer, BUFFER_LOCK_SHARE);
+
+			page = BufferGetPage(buffer);
+			if (PageIsAllVisible(page))
+				info->bits[blkno] |= (1 << 2);
+
+			UnlockReleaseBuffer(buffer);
+		}
+	}
+
+	/* Clean up. */
+	if (vmbuffer != InvalidBuffer)
+		ReleaseBuffer(vmbuffer);
+	relation_close(rel, AccessShareLock);
+
+	return info;
+}