Date: Fri, 8 May 2020 02:25:45 -0500
From: Justin Pryzby <pryzby@telsasoft.com>
To: pgsql-hackers@lists.postgresql.org
Subject: should INSERT SELECT use a BulkInsertState?
Message-ID: <20200508072545.GA9701@telsasoft.com>
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Precedence: bulk

Seems to me it should, at least conditionally.  At least if there's a function
scan or a relation or ..

I mentioned a bit about our use-case here:
https://www.postgresql.org/message-id/20200219173742.GA30939%40telsasoft.com
=> I'd prefer our loaders to write their own data rather than dirtying large
fractions of buffer cache and leaving it around for other backends to clean up.

commit 7f9e061363e58f30eee0cccc8a0e46f637bf137b
Author: Justin Pryzby <pryzbyj@telsasoft.com>
Date:   Fri May 8 02:17:32 2020 -0500

    Make INSERT SELECT use a BulkInsertState

diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 20a4c474cc..6da4325225 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -578,7 +578,7 @@ ExecInsert(ModifyTableState *mtstate,
 			table_tuple_insert_speculative(resultRelationDesc, slot,
 										   estate->es_output_cid,
 										   0,
-										   NULL,
+										   mtstate->bistate,
 										   specToken);
 
 			/* insert index entries for tuple */
@@ -617,7 +617,7 @@ ExecInsert(ModifyTableState *mtstate,
 			/* insert the tuple normally */
 			table_tuple_insert(resultRelationDesc, slot,
 							   estate->es_output_cid,
-							   0, NULL);
+							   0, mtstate->bistate);
 
 			/* insert index entries for tuple */
 			if (resultRelInfo->ri_NumIndices > 0)
@@ -2332,6 +2332,14 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 
 	mtstate->mt_arowmarks = (List **) palloc0(sizeof(List *) * nplans);
 	mtstate->mt_nplans = nplans;
+	mtstate->bistate = NULL;
+	if (operation == CMD_INSERT)
+	{
+		Plan *p = linitial(node->plans);
+		Assert(nplans == 1);
+		if (!IsA(p, Result) && !IsA(p, ValuesScan))
+			mtstate->bistate = GetBulkInsertState();
+	}
 
 	/* set up epqstate with dummy subplan data for the moment */
 	EvalPlanQualInit(&mtstate->mt_epqstate, estate, NULL, NIL, node->epqParam);
@@ -2809,6 +2817,9 @@ ExecEndModifyTable(ModifyTableState *node)
 	 */
 	for (i = 0; i < node->mt_nplans; i++)
 		ExecEndNode(node->mt_plans[i]);
+
+	if (node->bistate)
+		FreeBulkInsertState(node->bistate);
 }
 
 void
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 4fee043bb2..daf365f181 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -14,6 +14,7 @@
 #ifndef EXECNODES_H
 #define EXECNODES_H
 
+#include "access/heapam.h"
 #include "access/tupconvert.h"
 #include "executor/instrument.h"
 #include "fmgr.h"
@@ -1177,6 +1178,7 @@ typedef struct ModifyTableState
 	List	  **mt_arowmarks;	/* per-subplan ExecAuxRowMark lists */
 	EPQState	mt_epqstate;	/* for evaluating EvalPlanQual rechecks */
 	bool		fireBSTriggers; /* do we need to fire stmt triggers? */
+	BulkInsertState	bistate;	/* State for bulk insert like INSERT SELECT */
 
 	/*
 	 * Slot for storing tuples in the root partitioned table's rowtype during