From a65f4746b9cde8f19192d720d78c2edece5d26c2 Mon Sep 17 00:00:00 2001
From: "yizhi.fzh" <yizhi.fzh@alibaba-inc.com>
Date: Mon, 4 Dec 2023 14:22:03 +0800
Subject: [PATCH v1] A PoC code to show the benefit of eagerly detoast code
 path.

How to avoid this code path for the normal toast designed case needs                                    more discussion.
---
 src/backend/executor/execExprInterp.c | 17 +++++++++++++++++
 src/backend/executor/execTuples.c     | 16 ++++++++++++++++
 src/include/executor/tuptable.h       |  3 +++
 3 files changed, 36 insertions(+)

diff --git a/src/backend/executor/execExprInterp.c b/src/backend/executor/execExprInterp.c
index 24c2b60c62..062b3d884a 100644
--- a/src/backend/executor/execExprInterp.c
+++ b/src/backend/executor/execExprInterp.c
@@ -56,6 +56,7 @@
  */
 #include "postgres.h"
 
+#include "access/detoast.h"
 #include "access/heaptoast.h"
 #include "catalog/pg_type.h"
 #include "commands/sequence.h"
@@ -567,6 +568,12 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 			 * have an Assert to check that that did happen.
 			 */
 			Assert(attnum >= 0 && attnum < innerslot->tts_nvalid);
+
+			if (bms_is_member(attnum, innerslot->detoast_attrs) &&
+				!innerslot->tts_isnull[attnum])
+				innerslot->tts_values[attnum] = (Datum)  pg_detoast_datum(
+					(struct varlena *) innerslot->tts_values[attnum]);
+
 			*op->resvalue = innerslot->tts_values[attnum];
 			*op->resnull = innerslot->tts_isnull[attnum];
 
@@ -580,6 +587,11 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 			/* See EEOP_INNER_VAR comments */
 
 			Assert(attnum >= 0 && attnum < outerslot->tts_nvalid);
+			if (bms_is_member(attnum, outerslot->detoast_attrs) &&
+				!outerslot->tts_isnull[attnum])
+				outerslot->tts_values[attnum] = (Datum) pg_detoast_datum(
+					(struct varlena *) outerslot->tts_values[attnum]);
+
 			*op->resvalue = outerslot->tts_values[attnum];
 			*op->resnull = outerslot->tts_isnull[attnum];
 
@@ -593,6 +605,11 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 			/* See EEOP_INNER_VAR comments */
 
 			Assert(attnum >= 0 && attnum < scanslot->tts_nvalid);
+			if (bms_is_member(attnum, scanslot->detoast_attrs) &&
+				!scanslot->tts_isnull[attnum])
+				scanslot->tts_values[attnum] = (Datum) pg_detoast_datum(
+					(struct varlena *) scanslot->tts_values[attnum]);
+
 			*op->resvalue = scanslot->tts_values[attnum];
 			*op->resnull = scanslot->tts_isnull[attnum];
 
diff --git a/src/backend/executor/execTuples.c b/src/backend/executor/execTuples.c
index 2c2712ceac..629c45fb52 100644
--- a/src/backend/executor/execTuples.c
+++ b/src/backend/executor/execTuples.c
@@ -62,6 +62,7 @@
 #include "access/tupdesc_details.h"
 #include "catalog/pg_type.h"
 #include "funcapi.h"
+#include "jit/jit.h"
 #include "nodes/nodeFuncs.h"
 #include "storage/bufmgr.h"
 #include "utils/builtins.h"
@@ -1143,6 +1144,7 @@ MakeTupleTableSlot(TupleDesc tupleDesc,
 
 	if (tupleDesc != NULL)
 	{
+		int		i;
 		slot->tts_values = (Datum *)
 			(((char *) slot)
 			 + MAXALIGN(basesz));
@@ -1152,6 +1154,20 @@ MakeTupleTableSlot(TupleDesc tupleDesc,
 			 + MAXALIGN(tupleDesc->natts * sizeof(Datum)));
 
 		PinTupleDesc(tupleDesc);
+
+		/* not ready jit so far, it's OK for a poc patch. */
+		if (!jit_enabled)
+		{
+			for (i = 0; i < tupleDesc->natts; i++)
+			{
+				Form_pg_attribute attr = TupleDescAttr(tupleDesc, i);
+				if (attr->attlen == -1 && attr->attstorage != TYPSTORAGE_PLAIN)
+				{
+					slot->detoast_attrs = bms_add_member(slot->detoast_attrs,
+														 attr->attnum - 1);
+				}
+			}
+		}
 	}
 
 	/*
diff --git a/src/include/executor/tuptable.h b/src/include/executor/tuptable.h
index 4210d6d838..75779ed31f 100644
--- a/src/include/executor/tuptable.h
+++ b/src/include/executor/tuptable.h
@@ -18,6 +18,7 @@
 #include "access/htup_details.h"
 #include "access/sysattr.h"
 #include "access/tupdesc.h"
+#include "nodes/bitmapset.h"
 #include "storage/buf.h"
 
 /*----------
@@ -128,6 +129,8 @@ typedef struct TupleTableSlot
 	MemoryContext tts_mcxt;		/* slot itself is in this context */
 	ItemPointerData tts_tid;	/* stored tuple's tid */
 	Oid			tts_tableOid;	/* table oid of tuple */
+
+	Bitmapset  *detoast_attrs;  /* Index start from 0. */
 } TupleTableSlot;
 
 /* routines for a TupleTableSlot implementation */
-- 
2.34.1