v39-0001-Invent-HeapTupleGetRawDatum-and-friends.patch

From 8186bdc373418a407610959c16cc838a478feb5e Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Thu, 18 Mar 2021 12:20:00 -0400
Subject: [PATCH v39 1/4] Invent HeapTupleGetRawDatum and friends.

HeapTupleGetRawDatum, HeapTupleHeaderGetRawDatum, and
PG_RETURN_HEAPTUPLEHEADER_RAW, and heap_copy_tuple_as_raw_datum are
just like HeapTupleGetDatum, HeapTupleHeaderGetDatum,
PG_RETURN_HEAPTUPLEHEADER, and heap_copy_tuple_as_datum, except that
they don't check that the returned tuple is free of external datums.
Instead, the caller must guarantee that this is the case.

The overarching idea here is that it's usually more efficient for the
caller to make sure to build the tuple originally without any external
datums, rather than building a tuple that may contain external datums
and then invoking a function which will possibly deform that tuple,
detoast those fields, and build a replacement tuple. Fortunately, very
few places are relying on this behavior of the above functions, which
means that this patch can safely change practically all the calls to
the existing functions to use the "raw" variants.

In the places that continue to use the non-raw variants after this
patch, there is an opportunity to improve performance by fixing them
so that they can. That work is planned for a follow-up patch.

That said, the main motivation for this patch is actually to cut down
on the number of places that depend on HeapTupleHasExternal tests to
avoid performance problems, and to make it clear where the remaining
places are. New features - such as configurable TOAST compression -
will not have the luxury of consuming an infomask bit to indicate
whether or not they are in use somewhere inside a tuple.

Dilip Kumar, based on an idea by me. Documentation changes also by me.

Discussion: http://postgr.es/m/CAFiTN-u3jrRDiuyGxGvNSGDXLhG4=U2orHnjk4B6WBy9Eo9kMQ@mail.gmail.com
Discussion: http://postgr.es/m/CAFiTN-s8SsWs2zCZL3TFxXwi4VE35J%3D4aKpduKVrTaL%2B3wnB0A%40mail.gmail.com
---
 contrib/dblink/dblink.c                         |  2 +-
 contrib/hstore/hstore_io.c                      |  4 ++--
 contrib/hstore/hstore_op.c                      |  2 +-
 contrib/old_snapshot/time_mapping.c             |  2 +-
 contrib/pageinspect/brinfuncs.c                 |  2 +-
 contrib/pageinspect/btreefuncs.c                |  6 +++---
 contrib/pageinspect/ginfuncs.c                  |  6 +++---
 contrib/pageinspect/gistfuncs.c                 |  2 +-
 contrib/pageinspect/hashfuncs.c                 |  8 ++++----
 contrib/pageinspect/heapfuncs.c                 |  6 +++---
 contrib/pageinspect/rawpage.c                   |  2 +-
 contrib/pg_buffercache/pg_buffercache_pages.c   |  2 +-
 contrib/pg_stat_statements/pg_stat_statements.c |  3 ++-
 contrib/pg_visibility/pg_visibility.c           | 13 ++++++++-----
 contrib/pgcrypto/pgp-pgsql.c                    |  2 +-
 contrib/pgstattuple/pgstatapprox.c              |  2 +-
 contrib/pgstattuple/pgstatindex.c               |  6 +++---
 contrib/pgstattuple/pgstattuple.c               |  2 +-
 contrib/sslinfo/sslinfo.c                       |  2 +-
 doc/src/sgml/xfunc.sgml                         |  8 ++++++--
 src/backend/access/common/heaptuple.c           | 26 ++++++++++++++++++++-----
 src/backend/access/transam/commit_ts.c          |  4 ++--
 src/backend/access/transam/multixact.c          |  2 +-
 src/backend/access/transam/twophase.c           |  2 +-
 src/backend/access/transam/xlogfuncs.c          |  2 +-
 src/backend/catalog/objectaddress.c             |  6 +++---
 src/backend/commands/sequence.c                 |  2 +-
 src/backend/executor/execExprInterp.c           | 15 +++++++++-----
 src/backend/replication/slotfuncs.c             |  8 ++++----
 src/backend/replication/walreceiver.c           |  3 ++-
 src/backend/statistics/mcv.c                    |  2 +-
 src/backend/tsearch/wparser.c                   |  4 ++--
 src/backend/utils/adt/acl.c                     |  2 +-
 src/backend/utils/adt/datetime.c                |  2 +-
 src/backend/utils/adt/genfile.c                 |  2 +-
 src/backend/utils/adt/lockfuncs.c               |  4 ++--
 src/backend/utils/adt/misc.c                    |  4 ++--
 src/backend/utils/adt/partitionfuncs.c          |  2 +-
 src/backend/utils/adt/pgstatfuncs.c             |  6 ++++--
 src/backend/utils/adt/rowtypes.c                |  4 ++--
 src/backend/utils/adt/tsvector_op.c             |  4 ++--
 src/backend/utils/misc/guc.c                    |  2 +-
 src/backend/utils/misc/pg_controldata.c         |  8 ++++----
 src/include/access/htup_details.h               |  1 +
 src/include/fmgr.h                              |  8 ++++++++
 src/include/funcapi.h                           | 14 +++++++++++++
 src/pl/plperl/plperl.c                          |  4 ++--
 src/pl/tcl/pltcl.c                              |  4 ++--
 src/test/modules/test_predtest/test_predtest.c  |  3 ++-
 49 files changed, 144 insertions(+), 88 deletions(-)

diff --git a/contrib/dblink/dblink.c b/contrib/dblink/dblink.c
index 3a0beaa..5a41116 100644
--- a/contrib/dblink/dblink.c
+++ b/contrib/dblink/dblink.c
@@ -1630,7 +1630,7 @@ dblink_get_pkey(PG_FUNCTION_ARGS)
 		tuple = BuildTupleFromCStrings(attinmeta, values);
 
 		/* make the tuple into a datum */
-		result = HeapTupleGetDatum(tuple);
+		result = HeapTupleGetRawDatum(tuple);
 
 		SRF_RETURN_NEXT(funcctx, result);
 	}
diff --git a/contrib/hstore/hstore_io.c b/contrib/hstore/hstore_io.c
index b3304ff..cc7a8e0 100644
--- a/contrib/hstore/hstore_io.c
+++ b/contrib/hstore/hstore_io.c
@@ -1137,14 +1137,14 @@ hstore_populate_record(PG_FUNCTION_ARGS)
 	 * check domain constraints before deciding we're done.
 	 */
 	if (argtype != tupdesc->tdtypeid)
-		domain_check(HeapTupleGetDatum(rettuple), false,
+		domain_check(HeapTupleGetRawDatum(rettuple), false,
 					 argtype,
 					 &my_extra->domain_info,
 					 fcinfo->flinfo->fn_mcxt);
 
 	ReleaseTupleDesc(tupdesc);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(rettuple));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(rettuple->t_data);
 }
 
 
diff --git a/contrib/hstore/hstore_op.c b/contrib/hstore/hstore_op.c
index dd79d01..d466f6c 100644
--- a/contrib/hstore/hstore_op.c
+++ b/contrib/hstore/hstore_op.c
@@ -1067,7 +1067,7 @@ hstore_each(PG_FUNCTION_ARGS)
 		}
 
 		tuple = heap_form_tuple(funcctx->tuple_desc, dvalues, nulls);
-		res = HeapTupleGetDatum(tuple);
+		res = HeapTupleGetRawDatum(tuple);
 
 		SRF_RETURN_NEXT(funcctx, PointerGetDatum(res));
 	}
diff --git a/contrib/old_snapshot/time_mapping.c b/contrib/old_snapshot/time_mapping.c
index 3df0717..5d517c8 100644
--- a/contrib/old_snapshot/time_mapping.c
+++ b/contrib/old_snapshot/time_mapping.c
@@ -72,7 +72,7 @@ pg_old_snapshot_time_mapping(PG_FUNCTION_ARGS)
 
 		tuple = MakeOldSnapshotTimeMappingTuple(funcctx->tuple_desc, mapping);
 		++mapping->current_index;
-		SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(tuple));
+		SRF_RETURN_NEXT(funcctx, HeapTupleGetRawDatum(tuple));
 	}
 
 	SRF_RETURN_DONE(funcctx);
diff --git a/contrib/pageinspect/brinfuncs.c b/contrib/pageinspect/brinfuncs.c
index 0e3c2de..6262946 100644
--- a/contrib/pageinspect/brinfuncs.c
+++ b/contrib/pageinspect/brinfuncs.c
@@ -366,7 +366,7 @@ brin_metapage_info(PG_FUNCTION_ARGS)
 
 	htup = heap_form_tuple(tupdesc, values, nulls);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(htup));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(htup->t_data);
 }
 
 /*
diff --git a/contrib/pageinspect/btreefuncs.c b/contrib/pageinspect/btreefuncs.c
index b7725b5..f0028e4 100644
--- a/contrib/pageinspect/btreefuncs.c
+++ b/contrib/pageinspect/btreefuncs.c
@@ -263,7 +263,7 @@ bt_page_stats_internal(PG_FUNCTION_ARGS, enum pageinspect_version ext_version)
 	tuple = BuildTupleFromCStrings(TupleDescGetAttInMetadata(tupleDesc),
 								   values);
 
-	result = HeapTupleGetDatum(tuple);
+	result = HeapTupleGetRawDatum(tuple);
 
 	PG_RETURN_DATUM(result);
 }
@@ -436,7 +436,7 @@ bt_page_print_tuples(struct user_args *uargs)
 	/* Build and return the result tuple */
 	tuple = heap_form_tuple(uargs->tupd, values, nulls);
 
-	return HeapTupleGetDatum(tuple);
+	return HeapTupleGetRawDatum(tuple);
 }
 
 /*-------------------------------------------------------
@@ -766,7 +766,7 @@ bt_metap(PG_FUNCTION_ARGS)
 	tuple = BuildTupleFromCStrings(TupleDescGetAttInMetadata(tupleDesc),
 								   values);
 
-	result = HeapTupleGetDatum(tuple);
+	result = HeapTupleGetRawDatum(tuple);
 
 	UnlockReleaseBuffer(buffer);
 	relation_close(rel, AccessShareLock);
diff --git a/contrib/pageinspect/ginfuncs.c b/contrib/pageinspect/ginfuncs.c
index e425cbc..77dd559 100644
--- a/contrib/pageinspect/ginfuncs.c
+++ b/contrib/pageinspect/ginfuncs.c
@@ -82,7 +82,7 @@ gin_metapage_info(PG_FUNCTION_ARGS)
 	/* Build and return the result tuple. */
 	resultTuple = heap_form_tuple(tupdesc, values, nulls);
 
-	return HeapTupleGetDatum(resultTuple);
+	return HeapTupleGetRawDatum(resultTuple);
 }
 
 
@@ -150,7 +150,7 @@ gin_page_opaque_info(PG_FUNCTION_ARGS)
 	/* Build and return the result tuple. */
 	resultTuple = heap_form_tuple(tupdesc, values, nulls);
 
-	return HeapTupleGetDatum(resultTuple);
+	return HeapTupleGetRawDatum(resultTuple);
 }
 
 typedef struct gin_leafpage_items_state
@@ -254,7 +254,7 @@ gin_leafpage_items(PG_FUNCTION_ARGS)
 
 		/* Build and return the result tuple. */
 		resultTuple = heap_form_tuple(inter_call_data->tupd, values, nulls);
-		result = HeapTupleGetDatum(resultTuple);
+		result = HeapTupleGetRawDatum(resultTuple);
 
 		inter_call_data->seg = GinNextPostingListSegment(cur);
 
diff --git a/contrib/pageinspect/gistfuncs.c b/contrib/pageinspect/gistfuncs.c
index eb9f630..dbf34f8 100644
--- a/contrib/pageinspect/gistfuncs.c
+++ b/contrib/pageinspect/gistfuncs.c
@@ -89,7 +89,7 @@ gist_page_opaque_info(PG_FUNCTION_ARGS)
 	/* Build and return the result tuple. */
 	resultTuple = heap_form_tuple(tupdesc, values, nulls);
 
-	return HeapTupleGetDatum(resultTuple);
+	return HeapTupleGetRawDatum(resultTuple);
 }
 
 Datum
diff --git a/contrib/pageinspect/hashfuncs.c b/contrib/pageinspect/hashfuncs.c
index ff01119..957ee5b 100644
--- a/contrib/pageinspect/hashfuncs.c
+++ b/contrib/pageinspect/hashfuncs.c
@@ -273,7 +273,7 @@ hash_page_stats(PG_FUNCTION_ARGS)
 
 	tuple = heap_form_tuple(tupleDesc, values, nulls);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(tuple));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(tuple->t_data);
 }
 
 /*
@@ -368,7 +368,7 @@ hash_page_items(PG_FUNCTION_ARGS)
 		values[j] = Int64GetDatum((int64) hashkey);
 
 		tuple = heap_form_tuple(fctx->attinmeta->tupdesc, values, nulls);
-		result = HeapTupleGetDatum(tuple);
+		result = HeapTupleGetRawDatum(tuple);
 
 		uargs->offset = uargs->offset + 1;
 
@@ -499,7 +499,7 @@ hash_bitmap_info(PG_FUNCTION_ARGS)
 
 	tuple = heap_form_tuple(tupleDesc, values, nulls);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(tuple));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(tuple->t_data);
 }
 
 /* ------------------------------------------------
@@ -577,5 +577,5 @@ hash_metapage_info(PG_FUNCTION_ARGS)
 
 	tuple = heap_form_tuple(tupleDesc, values, nulls);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(tuple));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(tuple->t_data);
 }
diff --git a/contrib/pageinspect/heapfuncs.c b/contrib/pageinspect/heapfuncs.c
index f6760eb..3a050ee 100644
--- a/contrib/pageinspect/heapfuncs.c
+++ b/contrib/pageinspect/heapfuncs.c
@@ -282,7 +282,7 @@ heap_page_items(PG_FUNCTION_ARGS)
 
 		/* Build and return the result tuple. */
 		resultTuple = heap_form_tuple(inter_call_data->tupd, values, nulls);
-		result = HeapTupleGetDatum(resultTuple);
+		result = HeapTupleGetRawDatum(resultTuple);
 
 		inter_call_data->offset++;
 
@@ -540,7 +540,7 @@ heap_tuple_infomask_flags(PG_FUNCTION_ARGS)
 		values[0] = PointerGetDatum(construct_empty_array(TEXTOID));
 		values[1] = PointerGetDatum(construct_empty_array(TEXTOID));
 		tuple = heap_form_tuple(tupdesc, values, nulls);
-		PG_RETURN_DATUM(HeapTupleGetDatum(tuple));
+		PG_RETURN_HEAPTUPLEHEADER_RAW(tuple->t_data);
 	}
 
 	/* build set of raw flags */
@@ -618,5 +618,5 @@ heap_tuple_infomask_flags(PG_FUNCTION_ARGS)
 
 	/* Returns the record as Datum */
 	tuple = heap_form_tuple(tupdesc, values, nulls);
-	PG_RETURN_DATUM(HeapTupleGetDatum(tuple));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(tuple->t_data);
 }
diff --git a/contrib/pageinspect/rawpage.c b/contrib/pageinspect/rawpage.c
index 7272b21..e7aab86 100644
--- a/contrib/pageinspect/rawpage.c
+++ b/contrib/pageinspect/rawpage.c
@@ -328,7 +328,7 @@ page_header(PG_FUNCTION_ARGS)
 	memset(nulls, 0, sizeof(nulls));
 
 	tuple = heap_form_tuple(tupdesc, values, nulls);
-	result = HeapTupleGetDatum(tuple);
+	result = HeapTupleGetRawDatum(tuple);
 
 	PG_RETURN_DATUM(result);
 }
diff --git a/contrib/pg_buffercache/pg_buffercache_pages.c b/contrib/pg_buffercache/pg_buffercache_pages.c
index 1bd579f..1fd405e 100644
--- a/contrib/pg_buffercache/pg_buffercache_pages.c
+++ b/contrib/pg_buffercache/pg_buffercache_pages.c
@@ -230,7 +230,7 @@ pg_buffercache_pages(PG_FUNCTION_ARGS)
 
 		/* Build and return the tuple. */
 		tuple = heap_form_tuple(fctx->tupdesc, values, nulls);
-		result = HeapTupleGetDatum(tuple);
+		result = HeapTupleGetRawDatum(tuple);
 
 		SRF_RETURN_NEXT(funcctx, result);
 	}
diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index 62cccbf..7eb80d5 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -1922,7 +1922,8 @@ pg_stat_statements_info(PG_FUNCTION_ARGS)
 	values[0] = Int64GetDatum(stats.dealloc);
 	values[1] = TimestampTzGetDatum(stats.stats_reset);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(
+			heap_form_tuple(tupdesc, values, nulls)->t_data);
 }
 
 /*
diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c
index dd0c124..43bb2ab 100644
--- a/contrib/pg_visibility/pg_visibility.c
+++ b/contrib/pg_visibility/pg_visibility.c
@@ -97,7 +97,8 @@ pg_visibility_map(PG_FUNCTION_ARGS)
 
 	relation_close(rel, AccessShareLock);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(
+			heap_form_tuple(tupdesc, values, nulls)->t_data);
 }
 
 /*
@@ -156,7 +157,8 @@ pg_visibility(PG_FUNCTION_ARGS)
 
 	relation_close(rel, AccessShareLock);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(
+			heap_form_tuple(tupdesc, values, nulls)->t_data);
 }
 
 /*
@@ -197,7 +199,7 @@ pg_visibility_map_rel(PG_FUNCTION_ARGS)
 		info->next++;
 
 		tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
-		SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(tuple));
+		SRF_RETURN_NEXT(funcctx, HeapTupleGetRawDatum(tuple));
 	}
 
 	SRF_RETURN_DONE(funcctx);
@@ -243,7 +245,7 @@ pg_visibility_rel(PG_FUNCTION_ARGS)
 		info->next++;
 
 		tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
-		SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(tuple));
+		SRF_RETURN_NEXT(funcctx, HeapTupleGetRawDatum(tuple));
 	}
 
 	SRF_RETURN_DONE(funcctx);
@@ -303,7 +305,8 @@ pg_visibility_map_summary(PG_FUNCTION_ARGS)
 	values[0] = Int64GetDatum(all_visible);
 	values[1] = Int64GetDatum(all_frozen);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(
+			heap_form_tuple(tupdesc, values, nulls)->t_data);
 }
 
 /*
diff --git a/contrib/pgcrypto/pgp-pgsql.c b/contrib/pgcrypto/pgp-pgsql.c
index 0536bfb..333f7fd 100644
--- a/contrib/pgcrypto/pgp-pgsql.c
+++ b/contrib/pgcrypto/pgp-pgsql.c
@@ -973,7 +973,7 @@ pgp_armor_headers(PG_FUNCTION_ARGS)
 
 		/* build a tuple */
 		tuple = BuildTupleFromCStrings(funcctx->attinmeta, values);
-		SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(tuple));
+		SRF_RETURN_NEXT(funcctx, HeapTupleGetRawDatum(tuple));
 	}
 }
 
diff --git a/contrib/pgstattuple/pgstatapprox.c b/contrib/pgstattuple/pgstatapprox.c
index 1fe193b..147c8d2 100644
--- a/contrib/pgstattuple/pgstatapprox.c
+++ b/contrib/pgstattuple/pgstatapprox.c
@@ -314,5 +314,5 @@ pgstattuple_approx_internal(Oid relid, FunctionCallInfo fcinfo)
 	values[i++] = Float8GetDatum(stat.free_percent);
 
 	ret = heap_form_tuple(tupdesc, values, nulls);
-	return HeapTupleGetDatum(ret);
+	return HeapTupleGetRawDatum(ret);
 }
diff --git a/contrib/pgstattuple/pgstatindex.c b/contrib/pgstattuple/pgstatindex.c
index 5368bb3..7d74c31 100644
--- a/contrib/pgstattuple/pgstatindex.c
+++ b/contrib/pgstattuple/pgstatindex.c
@@ -362,7 +362,7 @@ pgstatindex_impl(Relation rel, FunctionCallInfo fcinfo)
 		tuple = BuildTupleFromCStrings(TupleDescGetAttInMetadata(tupleDesc),
 									   values);
 
-		result = HeapTupleGetDatum(tuple);
+		result = HeapTupleGetRawDatum(tuple);
 	}
 
 	return result;
@@ -571,7 +571,7 @@ pgstatginindex_internal(Oid relid, FunctionCallInfo fcinfo)
 	 * Build and return the tuple
 	 */
 	tuple = heap_form_tuple(tupleDesc, values, nulls);
-	result = HeapTupleGetDatum(tuple);
+	result = HeapTupleGetRawDatum(tuple);
 
 	return result;
 }
@@ -727,7 +727,7 @@ pgstathashindex(PG_FUNCTION_ARGS)
 	values[7] = Float8GetDatum(free_percent);
 	tuple = heap_form_tuple(tupleDesc, values, nulls);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(tuple));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(tuple->t_data);
 }
 
 /* -------------------------------------------------
diff --git a/contrib/pgstattuple/pgstattuple.c b/contrib/pgstattuple/pgstattuple.c
index 21fdeff..70b8bf0 100644
--- a/contrib/pgstattuple/pgstattuple.c
+++ b/contrib/pgstattuple/pgstattuple.c
@@ -147,7 +147,7 @@ build_pgstattuple_type(pgstattuple_type *stat, FunctionCallInfo fcinfo)
 	tuple = BuildTupleFromCStrings(attinmeta, values);
 
 	/* make the tuple into a datum */
-	return HeapTupleGetDatum(tuple);
+	return HeapTupleGetRawDatum(tuple);
 }
 
 /* ----------
diff --git a/contrib/sslinfo/sslinfo.c b/contrib/sslinfo/sslinfo.c
index 30cae0b..53801e9 100644
--- a/contrib/sslinfo/sslinfo.c
+++ b/contrib/sslinfo/sslinfo.c
@@ -460,7 +460,7 @@ ssl_extension_info(PG_FUNCTION_ARGS)
 
 		/* Build tuple */
 		tuple = heap_form_tuple(fctx->tupdesc, values, nulls);
-		result = HeapTupleGetDatum(tuple);
+		result = HeapTupleGetRawDatum(tuple);
 
 		if (BIO_free(membuf) != 1)
 			elog(ERROR, "could not free OpenSSL BIO structure");
diff --git a/doc/src/sgml/xfunc.sgml b/doc/src/sgml/xfunc.sgml
index 41bcc5b..7707400 100644
--- a/doc/src/sgml/xfunc.sgml
+++ b/doc/src/sgml/xfunc.sgml
@@ -2923,14 +2923,18 @@ HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values)
 
     <para>
      Once you have built a tuple to return from your function, it
-     must be converted into a <type>Datum</type>. Use:
+     must be converted into a <type>Datum</type>. Use one of the following:
 <programlisting>
 HeapTupleGetDatum(HeapTuple tuple)
+HeapTupleGetRawDatum(HeapTuple tuple)
 </programlisting>
      to convert a <structname>HeapTuple</structname> into a valid Datum.  This
      <type>Datum</type> can be returned directly if you intend to return
      just a single row, or it can be used as the current return value
-     in a set-returning function.
+     in a set-returning function. <literal>HeapTupleGetRawDatum</literal>
+     is more efficient and is preferred for new code, but the caller must
+     ensure that the tuple contains no external TOAST pointers. If this
+     is not certain, use <literal>HeapTupleGetDatum</literal>.
     </para>
 
     <para>
diff --git a/src/backend/access/common/heaptuple.c b/src/backend/access/common/heaptuple.c
index 0b56b0f..06479f5 100644
--- a/src/backend/access/common/heaptuple.c
+++ b/src/backend/access/common/heaptuple.c
@@ -983,8 +983,6 @@ heap_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc)
 Datum
 heap_copy_tuple_as_datum(HeapTuple tuple, TupleDesc tupleDesc)
 {
-	HeapTupleHeader td;
-
 	/*
 	 * If the tuple contains any external TOAST pointers, we have to inline
 	 * those fields to meet the conventions for composite-type Datums.
@@ -993,11 +991,29 @@ heap_copy_tuple_as_datum(HeapTuple tuple, TupleDesc tupleDesc)
 		return toast_flatten_tuple_to_datum(tuple->t_data,
 											tuple->t_len,
 											tupleDesc);
+	else
+		return heap_copy_tuple_as_raw_datum(tuple, tupleDesc);
+}
+
+/* ----------------
+ *		heap_copy_tuple_as_raw_datum
+ *
+ *		copy a tuple as a composite-type Datum, but the input tuple should not
+ *		contain any external data.
+ * ----------------
+ */
+Datum
+heap_copy_tuple_as_raw_datum(HeapTuple tuple, TupleDesc tupleDesc)
+{
+	HeapTupleHeader td;
+
+	/* The tuple should not contains any external TOAST pointers. */
+	Assert(!HeapTupleHasExternal(tuple));
 
 	/*
-	 * Fast path for easy case: just make a palloc'd copy and insert the
-	 * correct composite-Datum header fields (since those may not be set if
-	 * the given tuple came from disk, rather than from heap_form_tuple).
+	 * Just make a palloc'd copy and insert the correct composite-Datum
+	 * header fields (since those may not be set if the given tuple came
+	 * from disk, rather than from heap_form_tuple).
 	 */
 	td = (HeapTupleHeader) palloc(tuple->t_len);
 	memcpy((char *) td, (char *) tuple->t_data, tuple->t_len);
diff --git a/src/backend/access/transam/commit_ts.c b/src/backend/access/transam/commit_ts.c
index 48e8d66..015c841 100644
--- a/src/backend/access/transam/commit_ts.c
+++ b/src/backend/access/transam/commit_ts.c
@@ -469,7 +469,7 @@ pg_last_committed_xact(PG_FUNCTION_ARGS)
 
 	htup = heap_form_tuple(tupdesc, values, nulls);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(htup));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(htup->t_data);
 }
 
 /*
@@ -518,7 +518,7 @@ pg_xact_commit_timestamp_origin(PG_FUNCTION_ARGS)
 
 	htup = heap_form_tuple(tupdesc, values, nulls);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(htup));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(htup->t_data);
 }
 
 /*
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index 1f9f1a1..b44066a 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -3399,7 +3399,7 @@ pg_get_multixact_members(PG_FUNCTION_ARGS)
 
 		multi->iter++;
 		pfree(values[0]);
-		SRF_RETURN_NEXT(funccxt, HeapTupleGetDatum(tuple));
+		SRF_RETURN_NEXT(funccxt, HeapTupleGetRawDatum(tuple));
 	}
 
 	SRF_RETURN_DONE(funccxt);
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 6023e7c..3f48597 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -787,7 +787,7 @@ pg_prepared_xact(PG_FUNCTION_ARGS)
 		values[4] = ObjectIdGetDatum(proc->databaseId);
 
 		tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
-		result = HeapTupleGetDatum(tuple);
+		result = HeapTupleGetRawDatum(tuple);
 		SRF_RETURN_NEXT(funcctx, result);
 	}
 
diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c
index f363a4c..f60d6f1 100644
--- a/src/backend/access/transam/xlogfuncs.c
+++ b/src/backend/access/transam/xlogfuncs.c
@@ -487,7 +487,7 @@ pg_walfile_name_offset(PG_FUNCTION_ARGS)
 	 */
 	resultHeapTuple = heap_form_tuple(resultTupleDesc, values, isnull);
 
-	result = HeapTupleGetDatum(resultHeapTuple);
+	result = HeapTupleGetRawDatum(resultHeapTuple);
 
 	PG_RETURN_DATUM(result);
 }
diff --git a/src/backend/catalog/objectaddress.c b/src/backend/catalog/objectaddress.c
index 6d88b69..7cd62e7 100644
--- a/src/backend/catalog/objectaddress.c
+++ b/src/backend/catalog/objectaddress.c
@@ -2355,7 +2355,7 @@ pg_get_object_address(PG_FUNCTION_ARGS)
 
 	htup = heap_form_tuple(tupdesc, values, nulls);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(htup));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(htup->t_data);
 }
 
 /*
@@ -4233,7 +4233,7 @@ pg_identify_object(PG_FUNCTION_ARGS)
 
 	htup = heap_form_tuple(tupdesc, values, nulls);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(htup));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(htup->t_data);
 }
 
 /*
@@ -4304,7 +4304,7 @@ pg_identify_object_as_address(PG_FUNCTION_ARGS)
 
 	htup = heap_form_tuple(tupdesc, values, nulls);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(htup));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(htup->t_data);
 }
 
 /*
diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c
index 0415df9..f566e1e 100644
--- a/src/backend/commands/sequence.c
+++ b/src/backend/commands/sequence.c
@@ -1834,7 +1834,7 @@ pg_sequence_parameters(PG_FUNCTION_ARGS)
 
 	ReleaseSysCache(pgstuple);
 
-	return HeapTupleGetDatum(heap_form_tuple(tupdesc, values, isnull));
+	return HeapTupleGetRawDatum(heap_form_tuple(tupdesc, values, isnull));
 }
 
 /*
diff --git a/src/backend/executor/execExprInterp.c b/src/backend/executor/execExprInterp.c
index 6308286..e47ab1e 100644
--- a/src/backend/executor/execExprInterp.c
+++ b/src/backend/executor/execExprInterp.c
@@ -3169,8 +3169,13 @@ ExecEvalConvertRowtype(ExprState *state, ExprEvalStep *op, ExprContext *econtext
 	{
 		/* Full conversion with attribute rearrangement needed */
 		result = execute_attr_map_tuple(&tmptup, op->d.convert_rowtype.map);
-		/* Result already has appropriate composite-datum header fields */
-		*op->resvalue = HeapTupleGetDatum(result);
+
+		/*
+		 * Result already has appropriate composite-datum header fields. The
+		 * input was a composite type so we aren't expecting to have to
+		 * flatten any toasted fields so directly call HeapTupleGetRawDatum.
+		 */
+		*op->resvalue = HeapTupleGetRawDatum(result);
 	}
 	else
 	{
@@ -3181,10 +3186,10 @@ ExecEvalConvertRowtype(ExprState *state, ExprEvalStep *op, ExprContext *econtext
 		 * for this since it will both make the physical copy and insert the
 		 * correct composite header fields.  Note that we aren't expecting to
 		 * have to flatten any toasted fields: the input was a composite
-		 * datum, so it shouldn't contain any.  So heap_copy_tuple_as_datum()
-		 * is overkill here, but its check for external fields is cheap.
+		 * datum, so it shouldn't contain any.  So we can directly call
+		 * heap_copy_tuple_as_raw_datum().
 		 */
-		*op->resvalue = heap_copy_tuple_as_datum(&tmptup, outdesc);
+		*op->resvalue = heap_copy_tuple_as_raw_datum(&tmptup, outdesc);
 	}
 }
 
diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
index 9817b44..f92628b 100644
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -106,7 +106,7 @@ pg_create_physical_replication_slot(PG_FUNCTION_ARGS)
 		nulls[1] = true;
 
 	tuple = heap_form_tuple(tupdesc, values, nulls);
-	result = HeapTupleGetDatum(tuple);
+	result = HeapTupleGetRawDatum(tuple);
 
 	ReplicationSlotRelease();
 
@@ -205,7 +205,7 @@ pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
 	memset(nulls, 0, sizeof(nulls));
 
 	tuple = heap_form_tuple(tupdesc, values, nulls);
-	result = HeapTupleGetDatum(tuple);
+	result = HeapTupleGetRawDatum(tuple);
 
 	/* ok, slot is now fully created, mark it as persistent if needed */
 	if (!temporary)
@@ -689,7 +689,7 @@ pg_replication_slot_advance(PG_FUNCTION_ARGS)
 	nulls[1] = false;
 
 	tuple = heap_form_tuple(tupdesc, values, nulls);
-	result = HeapTupleGetDatum(tuple);
+	result = HeapTupleGetRawDatum(tuple);
 
 	PG_RETURN_DATUM(result);
 }
@@ -911,7 +911,7 @@ copy_replication_slot(FunctionCallInfo fcinfo, bool logical_slot)
 		nulls[1] = true;
 
 	tuple = heap_form_tuple(tupdesc, values, nulls);
-	result = HeapTupleGetDatum(tuple);
+	result = HeapTupleGetRawDatum(tuple);
 
 	ReplicationSlotRelease();
 
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index 8532296..f5425a3 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -1423,5 +1423,6 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
 	}
 
 	/* Returns the record as Datum */
-	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(
+			heap_form_tuple(tupdesc, values, nulls)->t_data);
 }
diff --git a/src/backend/statistics/mcv.c b/src/backend/statistics/mcv.c
index abbc1f1..115131c 100644
--- a/src/backend/statistics/mcv.c
+++ b/src/backend/statistics/mcv.c
@@ -1450,7 +1450,7 @@ pg_stats_ext_mcvlist_items(PG_FUNCTION_ARGS)
 		tuple = heap_form_tuple(funcctx->attinmeta->tupdesc, values, nulls);
 
 		/* make the tuple into a datum */
-		result = HeapTupleGetDatum(tuple);
+		result = HeapTupleGetRawDatum(tuple);
 
 		SRF_RETURN_NEXT(funcctx, result);
 	}
diff --git a/src/backend/tsearch/wparser.c b/src/backend/tsearch/wparser.c
index 71882dc..633c90d 100644
--- a/src/backend/tsearch/wparser.c
+++ b/src/backend/tsearch/wparser.c
@@ -97,7 +97,7 @@ tt_process_call(FuncCallContext *funcctx)
 		values[2] = st->list[st->cur].descr;
 
 		tuple = BuildTupleFromCStrings(funcctx->attinmeta, values);
-		result = HeapTupleGetDatum(tuple);
+		result = HeapTupleGetRawDatum(tuple);
 
 		pfree(values[1]);
 		pfree(values[2]);
@@ -236,7 +236,7 @@ prs_process_call(FuncCallContext *funcctx)
 		sprintf(tid, "%d", st->list[st->cur].type);
 		values[1] = st->list[st->cur].lexeme;
 		tuple = BuildTupleFromCStrings(funcctx->attinmeta, values);
-		result = HeapTupleGetDatum(tuple);
+		result = HeapTupleGetRawDatum(tuple);
 
 		pfree(values[1]);
 		st->cur++;
diff --git a/src/backend/utils/adt/acl.c b/src/backend/utils/adt/acl.c
index c7f029e..5871c0b 100644
--- a/src/backend/utils/adt/acl.c
+++ b/src/backend/utils/adt/acl.c
@@ -1804,7 +1804,7 @@ aclexplode(PG_FUNCTION_ARGS)
 			MemSet(nulls, 0, sizeof(nulls));
 
 			tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
-			result = HeapTupleGetDatum(tuple);
+			result = HeapTupleGetRawDatum(tuple);
 
 			SRF_RETURN_NEXT(funcctx, result);
 		}
diff --git a/src/backend/utils/adt/datetime.c b/src/backend/utils/adt/datetime.c
index 350b0c5..ce11554 100644
--- a/src/backend/utils/adt/datetime.c
+++ b/src/backend/utils/adt/datetime.c
@@ -4776,7 +4776,7 @@ pg_timezone_abbrevs(PG_FUNCTION_ARGS)
 	(*pindex)++;
 
 	tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
-	result = HeapTupleGetDatum(tuple);
+	result = HeapTupleGetRawDatum(tuple);
 
 	SRF_RETURN_NEXT(funcctx, result);
 }
diff --git a/src/backend/utils/adt/genfile.c b/src/backend/utils/adt/genfile.c
index 169ddf8..d3d386b 100644
--- a/src/backend/utils/adt/genfile.c
+++ b/src/backend/utils/adt/genfile.c
@@ -454,7 +454,7 @@ pg_stat_file(PG_FUNCTION_ARGS)
 
 	pfree(filename);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(tuple));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(tuple->t_data);
 }
 
 /*
diff --git a/src/backend/utils/adt/lockfuncs.c b/src/backend/utils/adt/lockfuncs.c
index 97f0265..0818449 100644
--- a/src/backend/utils/adt/lockfuncs.c
+++ b/src/backend/utils/adt/lockfuncs.c
@@ -344,7 +344,7 @@ pg_lock_status(PG_FUNCTION_ARGS)
 			nulls[15] = true;
 
 		tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
-		result = HeapTupleGetDatum(tuple);
+		result = HeapTupleGetRawDatum(tuple);
 		SRF_RETURN_NEXT(funcctx, result);
 	}
 
@@ -415,7 +415,7 @@ pg_lock_status(PG_FUNCTION_ARGS)
 		nulls[15] = true;
 
 		tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
-		result = HeapTupleGetDatum(tuple);
+		result = HeapTupleGetRawDatum(tuple);
 		SRF_RETURN_NEXT(funcctx, result);
 	}
 
diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index 634f574..57e0ea0 100644
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -484,7 +484,7 @@ pg_get_keywords(PG_FUNCTION_ARGS)
 
 		tuple = BuildTupleFromCStrings(funcctx->attinmeta, values);
 
-		SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(tuple));
+		SRF_RETURN_NEXT(funcctx, HeapTupleGetRawDatum(tuple));
 	}
 
 	SRF_RETURN_DONE(funcctx);
@@ -562,7 +562,7 @@ pg_get_catalog_foreign_keys(PG_FUNCTION_ARGS)
 
 		tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
 
-		SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(tuple));
+		SRF_RETURN_NEXT(funcctx, HeapTupleGetRawDatum(tuple));
 	}
 
 	SRF_RETURN_DONE(funcctx);
diff --git a/src/backend/utils/adt/partitionfuncs.c b/src/backend/utils/adt/partitionfuncs.c
index 03660d5..6915939 100644
--- a/src/backend/utils/adt/partitionfuncs.c
+++ b/src/backend/utils/adt/partitionfuncs.c
@@ -159,7 +159,7 @@ pg_partition_tree(PG_FUNCTION_ARGS)
 		values[3] = Int32GetDatum(level);
 
 		tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
-		result = HeapTupleGetDatum(tuple);
+		result = HeapTupleGetRawDatum(tuple);
 		SRF_RETURN_NEXT(funcctx, result);
 	}
 
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 5102227..b93ad73 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1856,7 +1856,8 @@ pg_stat_get_wal(PG_FUNCTION_ARGS)
 	values[8] = TimestampTzGetDatum(wal_stats->stat_reset_timestamp);
 
 	/* Returns the record as Datum */
-	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(
+			heap_form_tuple(tupdesc, values, nulls)->t_data);
 }
 
 /*
@@ -2272,7 +2273,8 @@ pg_stat_get_archiver(PG_FUNCTION_ARGS)
 		values[6] = TimestampTzGetDatum(archiver_stats->stat_reset_timestamp);
 
 	/* Returns the record as Datum */
-	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(
+			heap_form_tuple(tupdesc, values, nulls)->t_data);
 }
 
 /* Get the statistics for the replication slots */
diff --git a/src/backend/utils/adt/rowtypes.c b/src/backend/utils/adt/rowtypes.c
index 23787a6..079a5af 100644
--- a/src/backend/utils/adt/rowtypes.c
+++ b/src/backend/utils/adt/rowtypes.c
@@ -293,7 +293,7 @@ record_in(PG_FUNCTION_ARGS)
 	pfree(nulls);
 	ReleaseTupleDesc(tupdesc);
 
-	PG_RETURN_HEAPTUPLEHEADER(result);
+	PG_RETURN_HEAPTUPLEHEADER_RAW(result);
 }
 
 /*
@@ -660,7 +660,7 @@ record_recv(PG_FUNCTION_ARGS)
 	pfree(nulls);
 	ReleaseTupleDesc(tupdesc);
 
-	PG_RETURN_HEAPTUPLEHEADER(result);
+	PG_RETURN_HEAPTUPLEHEADER_RAW(result);
 }
 
 /*
diff --git a/src/backend/utils/adt/tsvector_op.c b/src/backend/utils/adt/tsvector_op.c
index 9236ebc..6679493 100644
--- a/src/backend/utils/adt/tsvector_op.c
+++ b/src/backend/utils/adt/tsvector_op.c
@@ -707,7 +707,7 @@ tsvector_unnest(PG_FUNCTION_ARGS)
 		}
 
 		tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
-		SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(tuple));
+		SRF_RETURN_NEXT(funcctx, HeapTupleGetRawDatum(tuple));
 	}
 	else
 	{
@@ -2385,7 +2385,7 @@ ts_process_call(FuncCallContext *funcctx)
 		values[2] = nentry;
 
 		tuple = BuildTupleFromCStrings(funcctx->attinmeta, values);
-		result = HeapTupleGetDatum(tuple);
+		result = HeapTupleGetRawDatum(tuple);
 
 		pfree(values[0]);
 
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index b263e34..6b2d9d6 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -9805,7 +9805,7 @@ show_all_settings(PG_FUNCTION_ARGS)
 		tuple = BuildTupleFromCStrings(attinmeta, values);
 
 		/* make the tuple into a datum */
-		result = HeapTupleGetDatum(tuple);
+		result = HeapTupleGetRawDatum(tuple);
 
 		SRF_RETURN_NEXT(funcctx, result);
 	}
diff --git a/src/backend/utils/misc/pg_controldata.c b/src/backend/utils/misc/pg_controldata.c
index 209a20a..195c127 100644
--- a/src/backend/utils/misc/pg_controldata.c
+++ b/src/backend/utils/misc/pg_controldata.c
@@ -73,7 +73,7 @@ pg_control_system(PG_FUNCTION_ARGS)
 
 	htup = heap_form_tuple(tupdesc, values, nulls);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(htup));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(htup->t_data);
 }
 
 Datum
@@ -204,7 +204,7 @@ pg_control_checkpoint(PG_FUNCTION_ARGS)
 
 	htup = heap_form_tuple(tupdesc, values, nulls);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(htup));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(htup->t_data);
 }
 
 Datum
@@ -257,7 +257,7 @@ pg_control_recovery(PG_FUNCTION_ARGS)
 
 	htup = heap_form_tuple(tupdesc, values, nulls);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(htup));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(htup->t_data);
 }
 
 Datum
@@ -340,5 +340,5 @@ pg_control_init(PG_FUNCTION_ARGS)
 
 	htup = heap_form_tuple(tupdesc, values, nulls);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(htup));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(htup->t_data);
 }
diff --git a/src/include/access/htup_details.h b/src/include/access/htup_details.h
index 7c62852..7ac3c23 100644
--- a/src/include/access/htup_details.h
+++ b/src/include/access/htup_details.h
@@ -790,6 +790,7 @@ extern Datum getmissingattr(TupleDesc tupleDesc,
 extern HeapTuple heap_copytuple(HeapTuple tuple);
 extern void heap_copytuple_with_tuple(HeapTuple src, HeapTuple dest);
 extern Datum heap_copy_tuple_as_datum(HeapTuple tuple, TupleDesc tupleDesc);
+extern Datum heap_copy_tuple_as_raw_datum(HeapTuple tuple, TupleDesc tupleDesc);
 extern HeapTuple heap_form_tuple(TupleDesc tupleDescriptor,
 								 Datum *values, bool *isnull);
 extern HeapTuple heap_modify_tuple(HeapTuple tuple,
diff --git a/src/include/fmgr.h b/src/include/fmgr.h
index ab7b85c..89eec72 100644
--- a/src/include/fmgr.h
+++ b/src/include/fmgr.h
@@ -372,7 +372,15 @@ extern struct varlena *pg_detoast_datum_packed(struct varlena *datum);
 #define PG_RETURN_TEXT_P(x)    PG_RETURN_POINTER(x)
 #define PG_RETURN_BPCHAR_P(x)  PG_RETURN_POINTER(x)
 #define PG_RETURN_VARCHAR_P(x) PG_RETURN_POINTER(x)
+
+/*
+ * A composite-type Datum must not contain external fields. To return a tuple
+ * that might, use PG_RETURN_HEAPTUPLEHEADER, which will build a replacement
+ * tuple without such fields if any are present. Otherwise, use
+ * PG_RETURN_HEAPTUPLEHEADER_RAW, which is slightly faster.
+ */
 #define PG_RETURN_HEAPTUPLEHEADER(x)  return HeapTupleHeaderGetDatum(x)
+#define PG_RETURN_HEAPTUPLEHEADER_RAW(x)  return HeapTupleHeaderGetRawDatum(x)
 
 
 /*-------------------------------------------------------------------------
diff --git a/src/include/funcapi.h b/src/include/funcapi.h
index 83e6bc2..92cc7bd 100644
--- a/src/include/funcapi.h
+++ b/src/include/funcapi.h
@@ -207,6 +207,8 @@ extern TupleDesc build_function_result_tupdesc_t(HeapTuple procTuple);
  *
  * Macro declarations:
  * HeapTupleGetDatum(HeapTuple tuple) - convert a HeapTuple to a Datum.
+ * HeapTupleGetRawDatum(HeapTuple tuple) - same, but must have no external
+ *      TOAST pointer
  *
  * Obsolete routines and macros:
  * TupleDesc RelationNameGetTupleDesc(const char *relname) - Use to get a
@@ -219,6 +221,7 @@ extern TupleDesc build_function_result_tupdesc_t(HeapTuple procTuple);
  */
 
 #define HeapTupleGetDatum(tuple)		HeapTupleHeaderGetDatum((tuple)->t_data)
+#define HeapTupleGetRawDatum(tuple)		HeapTupleHeaderGetRawDatum((tuple)->t_data)
 /* obsolete version of above */
 #define TupleGetDatum(_slot, _tuple)	HeapTupleGetDatum(_tuple)
 
@@ -231,6 +234,17 @@ extern AttInMetadata *TupleDescGetAttInMetadata(TupleDesc tupdesc);
 extern HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values);
 extern Datum HeapTupleHeaderGetDatum(HeapTupleHeader tuple);
 
+/*
+ * This is a faster version of HeapTupleHeaderGetDatum which can be used
+ * when it is known that no external TOAST pointers are present.
+ */
+static inline Datum
+HeapTupleHeaderGetRawDatum(HeapTupleHeader tuple)
+{
+	Assert(!HeapTupleHeaderHasExternal(tuple));
+	return PointerGetDatum(tuple);
+}
+
 
 /*----------
  *		Support for Set Returning Functions (SRFs)
diff --git a/src/pl/plperl/plperl.c b/src/pl/plperl/plperl.c
index 6299adf..cdf79f7 100644
--- a/src/pl/plperl/plperl.c
+++ b/src/pl/plperl/plperl.c
@@ -1127,7 +1127,7 @@ plperl_hash_to_datum(SV *src, TupleDesc td)
 {
 	HeapTuple	tup = plperl_build_tuple_result((HV *) SvRV(src), td);
 
-	return HeapTupleGetDatum(tup);
+	return HeapTupleGetRawDatum(tup);
 }
 
 /*
@@ -3334,7 +3334,7 @@ plperl_return_next_internal(SV *sv)
 										  current_call_data->ret_tdesc);
 
 		if (OidIsValid(current_call_data->cdomain_oid))
-			domain_check(HeapTupleGetDatum(tuple), false,
+			domain_check(HeapTupleGetRawDatum(tuple), false,
 						 current_call_data->cdomain_oid,
 						 &current_call_data->cdomain_info,
 						 rsi->econtext->ecxt_per_query_memory);
diff --git a/src/pl/tcl/pltcl.c b/src/pl/tcl/pltcl.c
index e118375..b4e710a 100644
--- a/src/pl/tcl/pltcl.c
+++ b/src/pl/tcl/pltcl.c
@@ -1024,7 +1024,7 @@ pltcl_func_handler(PG_FUNCTION_ARGS, pltcl_call_state *call_state,
 
 		tup = pltcl_build_tuple_result(interp, resultObjv, resultObjc,
 									   call_state);
-		retval = HeapTupleGetDatum(tup);
+		retval = HeapTupleGetRawDatum(tup);
 	}
 	else
 		retval = InputFunctionCall(&prodesc->result_in_func,
@@ -3235,7 +3235,7 @@ pltcl_build_tuple_result(Tcl_Interp *interp, Tcl_Obj **kvObjv, int kvObjc,
 
 	/* if result type is domain-over-composite, check domain constraints */
 	if (call_state->prodesc->fn_retisdomain)
-		domain_check(HeapTupleGetDatum(tuple), false,
+		domain_check(HeapTupleGetRawDatum(tuple), false,
 					 call_state->prodesc->result_typid,
 					 &call_state->prodesc->domain_info,
 					 call_state->prodesc->fn_cxt);
diff --git a/src/test/modules/test_predtest/test_predtest.c b/src/test/modules/test_predtest/test_predtest.c
index 9c0aadd..ec83645 100644
--- a/src/test/modules/test_predtest/test_predtest.c
+++ b/src/test/modules/test_predtest/test_predtest.c
@@ -214,5 +214,6 @@ test_predtest(PG_FUNCTION_ARGS)
 	values[6] = BoolGetDatum(s_r_holds);
 	values[7] = BoolGetDatum(w_r_holds);
 
-	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+	PG_RETURN_HEAPTUPLEHEADER_RAW(
+			heap_form_tuple(tupdesc, values, nulls)->t_data);
 }
-- 
1.8.3.1