From 889235087215aeaac27a7d1dde13f7b299f55cd7 Mon Sep 17 00:00:00 2001
From: Takayuki Tsunakawa <tsunakawa.takay@fujitsu.com>
Date: Tue, 9 Feb 2021 12:50:00 +0900
Subject: [PATCH v15] Fast COPY FROM into the foreign or sharded table.

This feature enables bulk COPY into foreign table in the case of
multi inserts is possible and foreign table has non-zero number of columns.

FDWAPI was extended by next routines:
* BeginForeignCopy
* EndForeignCopy
* ExecForeignCopy

BeginForeignCopy and EndForeignCopy initialize and free
the CopyState of bulk COPY. The ExecForeignCopy routine send
'COPY ... FROM STDIN' command to the foreign server, in iterative
manner send tuples by CopyTo() machinery, send EOF to this connection.

Code that constructed list of columns for a given foreign relation
in the deparseAnalyzeSql() routine is separated to the deparseRelColumnList().
It is reused in the deparseCopyFromSql().

Added TAP-tests on the specific corner cases of COPY FROM STDIN operation.

By the analogy of CopyFrom() the CopyState structure was extended
with data_dest_cb callback. It is used for send text representation
of a tuple to a custom destination.
The PgFdwModifyState structure is extended with the cstate field.
It is needed for avoid repeated initialization of CopyState. ALso for this
reason CopyTo() routine was split into the set of routines CopyToStart()/
CopyTo()/CopyToFinish().

When 0d5f05cde introduced support for using multi-insert mode when
copying into partitioned tables, it introduced single variable of
enum type CopyInsertMethod shared across all potential target
relations (partitions) that, along with some target relation
properties, dictated whether to engage multi-insert mode for a given
target relation.

Move that decision logic into InitResultRelInfo which now sets a new
boolean field ri_usesMultiInsert of ResultRelInfo when a target
relation is first initialized.  That prevents repeated computation
of the same information in some cases, especially for partitions,
and the new arrangement results in slightly more readability.
Enum CopyInsertMethod removed. This logic implements by ri_usesMultiInsert
field of the ResultRelInfo structure.

Authors: Andrey Lepikhov, Ashutosh Bapat, Amit Langote, Takayuki Tsunakawa
Reviewed-by: Ashutosh Bapat, Amit Langote, Takayuki Tsunakawa
Discussion:
https://www.postgresql.org/message-id/flat/3d0909dc-3691-a576-208a-90986e55489f%40postgrespro.ru
---
 contrib/postgres_fdw/deparse.c                 |  60 ++++--
 contrib/postgres_fdw/expected/postgres_fdw.out |  46 ++++-
 contrib/postgres_fdw/postgres_fdw.c            | 143 +++++++++++++
 contrib/postgres_fdw/postgres_fdw.h            |   1 +
 contrib/postgres_fdw/sql/postgres_fdw.sql      |  45 +++++
 doc/src/sgml/fdwhandler.sgml                   |  73 +++++++
 src/backend/commands/copy.c                    |   4 +-
 src/backend/commands/copyfrom.c                | 269 +++++++++++--------------
 src/backend/commands/copyto.c                  |  84 ++++++--
 src/backend/executor/execMain.c                |  52 +++++
 src/backend/executor/execPartition.c           |  34 +++-
 src/include/commands/copy.h                    |   8 +-
 src/include/commands/copyfrom_internal.h       |  10 -
 src/include/executor/execPartition.h           |   2 +
 src/include/executor/executor.h                |   2 +
 src/include/foreign/fdwapi.h                   |  15 ++
 src/include/nodes/execnodes.h                  |   8 +-
 17 files changed, 649 insertions(+), 207 deletions(-)

diff --git a/contrib/postgres_fdw/deparse.c b/contrib/postgres_fdw/deparse.c
index 6faf499..71e0538c 100644
--- a/contrib/postgres_fdw/deparse.c
+++ b/contrib/postgres_fdw/deparse.c
@@ -184,6 +184,8 @@ static void appendAggOrderBy(List *orderList, List *targetList,
 static void appendFunctionName(Oid funcid, deparse_expr_cxt *context);
 static Node *deparseSortGroupClause(Index ref, List *tlist, bool force_colno,
 									deparse_expr_cxt *context);
+static List *deparseRelColumnList(StringInfo buf, Relation rel,
+								  bool enclose_in_parens);
 
 /*
  * Helper functions
@@ -1859,6 +1861,20 @@ deparseUpdateSql(StringInfo buf, RangeTblEntry *rte,
 }
 
 /*
+ * Deparse COPY FROM into given buf.
+ * We need to use list of parameters at each query.
+ */
+void
+deparseCopyFromSql(StringInfo buf, Relation rel)
+{
+	appendStringInfoString(buf, "COPY ");
+	deparseRelation(buf, rel);
+	(void) deparseRelColumnList(buf, rel, true);
+
+	appendStringInfoString(buf, " FROM STDIN ");
+}
+
+/*
  * deparse remote UPDATE statement
  *
  * 'buf' is the output buffer to append the statement to
@@ -2119,6 +2135,30 @@ deparseAnalyzeSizeSql(StringInfo buf, Relation rel)
 void
 deparseAnalyzeSql(StringInfo buf, Relation rel, List **retrieved_attrs)
 {
+	appendStringInfoString(buf, "SELECT ");
+	*retrieved_attrs = deparseRelColumnList(buf, rel, false);
+
+	/* Don't generate bad syntax for zero-column relation. */
+	if (list_length(*retrieved_attrs) == 0)
+		appendStringInfoString(buf, "NULL");
+
+	/*
+	 * Construct FROM clause
+	 */
+	appendStringInfoString(buf, " FROM ");
+	deparseRelation(buf, rel);
+}
+
+/*
+ * Construct the list of columns of given foreign relation in the order they
+ * appear in the tuple descriptor of the relation. Ignore any dropped columns.
+ * Use column names on the foreign server instead of local names.
+ *
+ * Optionally enclose the list in parantheses.
+ */
+static List *
+deparseRelColumnList(StringInfo buf, Relation rel, bool enclose_in_parens)
+{
 	Oid			relid = RelationGetRelid(rel);
 	TupleDesc	tupdesc = RelationGetDescr(rel);
 	int			i;
@@ -2126,10 +2166,8 @@ deparseAnalyzeSql(StringInfo buf, Relation rel, List **retrieved_attrs)
 	List	   *options;
 	ListCell   *lc;
 	bool		first = true;
+	List	   *retrieved_attrs = NIL;
 
-	*retrieved_attrs = NIL;
-
-	appendStringInfoString(buf, "SELECT ");
 	for (i = 0; i < tupdesc->natts; i++)
 	{
 		/* Ignore dropped columns. */
@@ -2138,6 +2176,9 @@ deparseAnalyzeSql(StringInfo buf, Relation rel, List **retrieved_attrs)
 
 		if (!first)
 			appendStringInfoString(buf, ", ");
+		else if (enclose_in_parens)
+			appendStringInfoChar(buf, '(');
+
 		first = false;
 
 		/* Use attribute name or column_name option. */
@@ -2157,18 +2198,13 @@ deparseAnalyzeSql(StringInfo buf, Relation rel, List **retrieved_attrs)
 
 		appendStringInfoString(buf, quote_identifier(colname));
 
-		*retrieved_attrs = lappend_int(*retrieved_attrs, i + 1);
+		retrieved_attrs = lappend_int(retrieved_attrs, i + 1);
 	}
 
-	/* Don't generate bad syntax for zero-column relation. */
-	if (first)
-		appendStringInfoString(buf, "NULL");
+	if (enclose_in_parens && list_length(retrieved_attrs) > 0)
+		appendStringInfoChar(buf, ')');
 
-	/*
-	 * Construct FROM clause
-	 */
-	appendStringInfoString(buf, " FROM ");
-	deparseRelation(buf, rel);
+	return retrieved_attrs;
 }
 
 /*
diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 60c7e11..dd310bb 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8111,8 +8111,9 @@ copy rem2 from stdin;
 copy rem2 from stdin; -- ERROR
 ERROR:  new row for relation "loc2" violates check constraint "loc2_f1positive"
 DETAIL:  Failing row contains (-1, xyzzy).
-CONTEXT:  remote SQL command: INSERT INTO public.loc2(f1, f2) VALUES ($1, $2)
-COPY rem2, line 1: "-1	xyzzy"
+CONTEXT:  COPY loc2, line 1: "-1	xyzzy"
+remote SQL command: COPY public.loc2(f1, f2) FROM STDIN 
+COPY rem2, line 2
 select * from rem2;
  f1 | f2  
 ----+-----
@@ -8123,6 +8124,19 @@ select * from rem2;
 alter foreign table rem2 drop constraint rem2_f1positive;
 alter table loc2 drop constraint loc2_f1positive;
 delete from rem2;
+create table foo (a int) partition by list (a);
+create table foo1 (like foo);
+create foreign table ffoo1 partition of foo for values in (1)
+	server loopback options (table_name 'foo1');
+create table foo2 (like foo);
+create foreign table ffoo2 partition of foo for values in (2)
+	server loopback options (table_name 'foo2');
+create function print_new_row() returns trigger language plpgsql as $$
+	begin raise notice '%', new; return new; end; $$;
+create trigger ffoo1_br_trig before insert on ffoo1
+	for each row execute function print_new_row();
+copy foo from stdin;
+NOTICE:  (1)
 -- Test local triggers
 create trigger trig_stmt_before before insert on rem2
 	for each statement execute procedure trigger_func();
@@ -8231,6 +8245,34 @@ drop trigger rem2_trig_row_before on rem2;
 drop trigger rem2_trig_row_after on rem2;
 drop trigger loc2_trig_row_before_insert on loc2;
 delete from rem2;
+alter table loc2 drop column f1;
+alter table loc2 drop column f2;
+copy rem2 from stdin;
+ERROR:  column "f1" of relation "loc2" does not exist
+CONTEXT:  remote SQL command: COPY public.loc2(f1, f2) FROM STDIN 
+COPY rem2, line 3
+alter table loc2 add column f1 int;
+alter table loc2 add column f2 int;
+select * from rem2;
+ f1 | f2 
+----+----
+(0 rows)
+
+-- dropped columns locally and on the foreign server
+alter table rem2 drop column f1;
+alter table rem2 drop column f2;
+copy rem2 from stdin;
+select * from rem2;
+--
+(2 rows)
+
+alter table loc2 drop column f1;
+alter table loc2 drop column f2;
+copy rem2 from stdin;
+select * from rem2;
+--
+(4 rows)
+
 -- test COPY FROM with foreign table created in the same transaction
 create table loc3 (f1 int, f2 text);
 begin;
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index 368997d..ed872e9 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -18,6 +18,7 @@
 #include "access/sysattr.h"
 #include "access/table.h"
 #include "catalog/pg_class.h"
+#include "commands/copy.h"
 #include "commands/defrem.h"
 #include "commands/explain.h"
 #include "commands/vacuum.h"
@@ -201,6 +202,7 @@ typedef struct PgFdwModifyState
 	/* for update row movement if subplan result rel */
 	struct PgFdwModifyState *aux_fmstate;	/* foreign-insert state, if
 											 * created */
+	CopyToState cstate; /* foreign COPY state, if used */
 } PgFdwModifyState;
 
 /*
@@ -373,6 +375,13 @@ static void postgresBeginForeignInsert(ModifyTableState *mtstate,
 									   ResultRelInfo *resultRelInfo);
 static void postgresEndForeignInsert(EState *estate,
 									 ResultRelInfo *resultRelInfo);
+static void postgresBeginForeignCopy(ModifyTableState *mtstate,
+									   ResultRelInfo *resultRelInfo);
+static void postgresEndForeignCopy(EState *estate,
+									 ResultRelInfo *resultRelInfo);
+static void postgresExecForeignCopy(ResultRelInfo *resultRelInfo,
+									  TupleTableSlot **slots,
+									  int nslots);
 static int	postgresIsForeignRelUpdatable(Relation rel);
 static bool postgresPlanDirectModify(PlannerInfo *root,
 									 ModifyTable *plan,
@@ -558,6 +567,9 @@ postgres_fdw_handler(PG_FUNCTION_ARGS)
 	routine->EndForeignModify = postgresEndForeignModify;
 	routine->BeginForeignInsert = postgresBeginForeignInsert;
 	routine->EndForeignInsert = postgresEndForeignInsert;
+	routine->BeginForeignCopy = postgresBeginForeignCopy;
+	routine->ExecForeignCopy = postgresExecForeignCopy;
+	routine->EndForeignCopy = postgresEndForeignCopy;
 	routine->IsForeignRelUpdatable = postgresIsForeignRelUpdatable;
 	routine->PlanDirectModify = postgresPlanDirectModify;
 	routine->BeginDirectModify = postgresBeginDirectModify;
@@ -2169,6 +2181,137 @@ postgresEndForeignInsert(EState *estate,
 	finish_foreign_modify(fmstate);
 }
 
+static PgFdwModifyState *copy_fmstate = NULL;
+
+static void
+pgfdw_copy_dest_cb(void *buf, int len)
+{
+	PGconn *conn = copy_fmstate->conn;
+
+	if (PQputCopyData(conn, (char *) buf, len) <= 0)
+		pgfdw_report_error(ERROR, NULL, conn, false, copy_fmstate->query);
+}
+
+/*
+ * postgresBeginForeignCopy
+ *		Begin an COPY operation on a foreign table
+ */
+static void
+postgresBeginForeignCopy(ModifyTableState *mtstate,
+						   ResultRelInfo *resultRelInfo)
+{
+	PgFdwModifyState *fmstate;
+	EState	   *estate = mtstate->ps.state;
+	StringInfoData sql;
+	RangeTblEntry *rte;
+	Relation rel = resultRelInfo->ri_RelationDesc;
+
+	if (resultRelInfo->ri_RangeTableIndex == 0)
+	{
+		ResultRelInfo *rootResultRelInfo = resultRelInfo->ri_RootResultRelInfo;
+
+		rte = exec_rt_fetch(rootResultRelInfo->ri_RangeTableIndex, estate);
+		rte = copyObject(rte);
+		rte->relid = RelationGetRelid(rel);
+		rte->relkind = RELKIND_FOREIGN_TABLE;
+	}
+	else
+		rte = exec_rt_fetch(resultRelInfo->ri_RangeTableIndex, estate);
+
+	initStringInfo(&sql);
+	deparseCopyFromSql(&sql, rel);
+
+	fmstate = create_foreign_modify(mtstate->ps.state,
+									rte,
+									resultRelInfo,
+									CMD_INSERT,
+									NULL,
+									sql.data,
+									NIL,
+									-1,
+									false,
+									NIL);
+
+	fmstate->cstate = BeginCopyTo(NULL, NULL, RelationGetDescr(rel), NULL,
+								  InvalidOid, NULL, false, pgfdw_copy_dest_cb,
+								  NIL, NIL);
+	CopyToStart(fmstate->cstate);
+	resultRelInfo->ri_FdwState = fmstate;
+}
+
+/*
+ * postgresExecForeignCopy
+ *		Send a number of tuples to the foreign relation.
+ */
+static void
+postgresExecForeignCopy(ResultRelInfo *resultRelInfo,
+						  TupleTableSlot **slots, int nslots)
+{
+	PgFdwModifyState *fmstate = resultRelInfo->ri_FdwState;
+	PGresult *res;
+	PGconn *conn = fmstate->conn;
+	bool OK = false;
+	int i;
+
+	/* Check correct use of CopyIn FDW API. */
+	Assert(fmstate->cstate != NULL);
+
+	res = PQexec(conn, fmstate->query);
+	if (PQresultStatus(res) != PGRES_COPY_IN)
+		pgfdw_report_error(ERROR, res, conn, true, fmstate->query);
+	PQclear(res);
+
+	PG_TRY();
+	{
+		copy_fmstate = fmstate;
+		for (i = 0; i < nslots; i++)
+			CopyOneRowTo(fmstate->cstate, slots[i]);
+
+		OK = true;
+	}
+	PG_FINALLY();
+	{
+		/*
+		 * Finish COPY IN protocol. It is needed to do after successful copy or
+		 * after an error.
+		 */
+		if (PQputCopyEnd(conn, OK ? NULL : _("canceled by server")) <= 0 ||
+			PQflush(conn))
+			pgfdw_report_error(ERROR, NULL, fmstate->conn, false, fmstate->query);
+
+		/* After successfully  sending an EOF signal, check command OK. */
+		res = PQgetResult(conn);
+		if ((!OK && PQresultStatus(res) != PGRES_FATAL_ERROR) ||
+			(OK && PQresultStatus(res) != PGRES_COMMAND_OK))
+			pgfdw_report_error(ERROR, res, fmstate->conn, true, fmstate->query);
+
+		PQclear(res);
+		/* Do this to ensure we've pumped libpq back to idle state */
+		if (PQgetResult(conn) != NULL)
+			ereport(ERROR,
+					(errmsg("unexpected extra results during COPY of table: %s",
+							PQerrorMessage(conn))));
+	}
+	PG_END_TRY();
+}
+
+/*
+ * postgresEndForeignCopy
+ *		Finish an COPY operation on a foreign table
+ */
+static void
+postgresEndForeignCopy(EState *estate, ResultRelInfo *resultRelInfo)
+{
+	PgFdwModifyState *fmstate = (PgFdwModifyState *) resultRelInfo->ri_FdwState;
+
+	/* Check correct use of CopyIn FDW API. */
+	Assert(fmstate->cstate != NULL);
+	CopyToFinish(fmstate->cstate);
+	pfree(fmstate->cstate);
+	fmstate->cstate = NULL;
+	finish_foreign_modify(fmstate);
+}
+
 /*
  * postgresIsForeignRelUpdatable
  *		Determine whether a foreign table supports INSERT, UPDATE and/or
diff --git a/contrib/postgres_fdw/postgres_fdw.h b/contrib/postgres_fdw/postgres_fdw.h
index 1f67b4d..cb801c9 100644
--- a/contrib/postgres_fdw/postgres_fdw.h
+++ b/contrib/postgres_fdw/postgres_fdw.h
@@ -165,6 +165,7 @@ extern void deparseInsertSql(StringInfo buf, RangeTblEntry *rte,
 extern void rebuildInsertSql(StringInfo buf, char *orig_query,
 							 int values_end_len, int num_cols,
 							 int num_rows);
+extern void deparseCopyFromSql(StringInfo buf, Relation rel);
 extern void deparseUpdateSql(StringInfo buf, RangeTblEntry *rte,
 							 Index rtindex, Relation rel,
 							 List *targetAttrs,
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index 151f4f1..e0d54ef 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -2235,6 +2235,23 @@ alter table loc2 drop constraint loc2_f1positive;
 
 delete from rem2;
 
+create table foo (a int) partition by list (a);
+create table foo1 (like foo);
+create foreign table ffoo1 partition of foo for values in (1)
+	server loopback options (table_name 'foo1');
+create table foo2 (like foo);
+create foreign table ffoo2 partition of foo for values in (2)
+	server loopback options (table_name 'foo2');
+create function print_new_row() returns trigger language plpgsql as $$
+	begin raise notice '%', new; return new; end; $$;
+create trigger ffoo1_br_trig before insert on ffoo1
+	for each row execute function print_new_row();
+
+copy foo from stdin;
+1
+2
+\.
+
 -- Test local triggers
 create trigger trig_stmt_before before insert on rem2
 	for each statement execute procedure trigger_func();
@@ -2335,6 +2352,34 @@ drop trigger loc2_trig_row_before_insert on loc2;
 
 delete from rem2;
 
+alter table loc2 drop column f1;
+alter table loc2 drop column f2;
+copy rem2 from stdin;
+1	foo
+2	bar
+\.
+
+alter table loc2 add column f1 int;
+alter table loc2 add column f2 int;
+select * from rem2;
+
+-- dropped columns locally and on the foreign server
+alter table rem2 drop column f1;
+alter table rem2 drop column f2;
+copy rem2 from stdin;
+
+
+\.
+select * from rem2;
+
+alter table loc2 drop column f1;
+alter table loc2 drop column f2;
+copy rem2 from stdin;
+
+
+\.
+select * from rem2;
+
 -- test COPY FROM with foreign table created in the same transaction
 create table loc3 (f1 int, f2 text);
 begin;
diff --git a/doc/src/sgml/fdwhandler.sgml b/doc/src/sgml/fdwhandler.sgml
index 854913a..ecc6273 100644
--- a/doc/src/sgml/fdwhandler.sgml
+++ b/doc/src/sgml/fdwhandler.sgml
@@ -1068,6 +1068,79 @@ EndDirectModify(ForeignScanState *node);
 
     <para>
 <programlisting>
+void
+BeginForeignCopy(ModifyTableState *mtstate,
+                   ResultRelInfo *rinfo);
+</programlisting>
+
+     Begin executing an copy operation on a foreign table. This routine is
+     called right before the first call of <function>ExecForeignCopy</function>
+     routine for the foreign table. It should perform any initialization needed
+     prior to the actual COPY FROM operation.
+     Subsequently, <function>ExecForeignCopy</function> will be called for
+     a bulk of tuples to be copied into the foreign table.
+    </para>
+
+    <para>
+     <literal>mtstate</literal> is the overall state of the
+     <structname>ModifyTable</structname> plan node being executed; global data about
+     the plan and execution state is available via this structure.
+     <literal>rinfo</literal> is the <structname>ResultRelInfo</structname> struct describing
+     the target foreign table.  (The <structfield>ri_FdwState</structfield> field of
+     <structname>ResultRelInfo</structname> is available for the FDW to store any
+     private state it needs for this operation.)
+    </para>
+
+    <para>
+     When this is called by a <command>COPY FROM</command> command, the
+     plan-related global data in <literal>mtstate</literal> is not provided.
+    </para>
+
+    <para>
+     If the <function>BeginForeignCopy</function> pointer is set to
+     <literal>NULL</literal>, no action is taken for the initialization.
+    </para>
+
+    <para>
+<programlisting>
+void
+ExecForeignCopy(ResultRelInfo *rinfo,
+                  TupleTableSlot **slots,
+                  int nslots);
+</programlisting>
+
+     Copy a bulk of tuples into the foreign table.
+      <literal>rinfo</literal> is the <structname>ResultRelInfo</structname> struct describing
+     the target foreign table.
+     <literal>slots</literal> contains the tuples to be inserted; it will match the
+     row-type definition of the foreign table.
+     <literal>nslots</literal> is a number of tuples in the <literal>slots</literal>
+    </para>
+
+    <para>
+     If the <function>ExecForeignCopy</function> pointer is set to
+     <literal>NULL</literal>, the <function>ExecForeignInsert</function> routine will be used to run COPY on the foreign table.
+    </para>
+
+    <para>
+<programlisting>
+void
+EndForeignCopy(EState *estate,
+                 ResultRelInfo *rinfo);
+</programlisting>
+
+     End the copy operation and release resources.  It is normally not important
+     to release palloc'd memory, but for example open files and connections
+     to remote servers should be cleaned up.
+    </para>
+
+    <para>
+     If the <function>EndForeignCopy</function> pointer is set to
+     <literal>NULL</literal>, no action is taken for the termination.
+    </para>
+
+    <para>
+<programlisting>
 RowMarkType
 GetForeignRowMarkType(RangeTblEntry *rte,
                       LockClauseStrength strength);
diff --git a/src/backend/commands/copy.c b/src/backend/commands/copy.c
index 8c712c8..cd8aa57 100644
--- a/src/backend/commands/copy.c
+++ b/src/backend/commands/copy.c
@@ -303,8 +303,8 @@ DoCopy(ParseState *pstate, const CopyStmt *stmt,
 	{
 		CopyToState cstate;
 
-		cstate = BeginCopyTo(pstate, rel, query, relid,
-							 stmt->filename, stmt->is_program,
+		cstate = BeginCopyTo(pstate, rel, NULL, query, relid,
+							 stmt->filename, stmt->is_program, NULL,
 							 stmt->attlist, stmt->options);
 		*processed = DoCopyTo(cstate);	/* copy from database to file */
 		EndCopyTo(cstate);
diff --git a/src/backend/commands/copyfrom.c b/src/backend/commands/copyfrom.c
index 796ca7b..4ee5c70 100644
--- a/src/backend/commands/copyfrom.c
+++ b/src/backend/commands/copyfrom.c
@@ -316,54 +316,64 @@ CopyMultiInsertBufferFlush(CopyMultiInsertInfo *miinfo,
 	cstate->line_buf_valid = false;
 	save_cur_lineno = cstate->cur_lineno;
 
-	/*
-	 * table_multi_insert may leak memory, so switch to short-lived memory
-	 * context before calling it.
-	 */
-	oldcontext = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
-	table_multi_insert(resultRelInfo->ri_RelationDesc,
-					   slots,
-					   nused,
-					   mycid,
-					   ti_options,
-					   buffer->bistate);
-	MemoryContextSwitchTo(oldcontext);
-
-	for (i = 0; i < nused; i++)
+	if (resultRelInfo->ri_RelationDesc->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
+	{
+		/* Flush into foreign table or partition */
+		resultRelInfo->ri_FdwRoutine->ExecForeignCopy(resultRelInfo,
+														slots,
+														nused);
+	}
+	else
 	{
 		/*
-		 * If there are any indexes, update them for all the inserted tuples,
-		 * and run AFTER ROW INSERT triggers.
+		 * table_multi_insert may leak memory, so switch to short-lived memory
+		 * context before calling it.
 		 */
-		if (resultRelInfo->ri_NumIndices > 0)
-		{
-			List	   *recheckIndexes;
-
-			cstate->cur_lineno = buffer->linenos[i];
-			recheckIndexes =
-				ExecInsertIndexTuples(resultRelInfo,
-									  buffer->slots[i], estate, false, false,
-									  NULL, NIL);
-			ExecARInsertTriggers(estate, resultRelInfo,
-								 slots[i], recheckIndexes,
-								 cstate->transition_capture);
-			list_free(recheckIndexes);
-		}
+		oldcontext = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
+		table_multi_insert(resultRelInfo->ri_RelationDesc,
+						   slots,
+						   nused,
+						   mycid,
+						   ti_options,
+						   buffer->bistate);
+		MemoryContextSwitchTo(oldcontext);
 
-		/*
-		 * There's no indexes, but see if we need to run AFTER ROW INSERT
-		 * triggers anyway.
-		 */
-		else if (resultRelInfo->ri_TrigDesc != NULL &&
-				 (resultRelInfo->ri_TrigDesc->trig_insert_after_row ||
-				  resultRelInfo->ri_TrigDesc->trig_insert_new_table))
+		for (i = 0; i < nused; i++)
 		{
-			cstate->cur_lineno = buffer->linenos[i];
-			ExecARInsertTriggers(estate, resultRelInfo,
-								 slots[i], NIL, cstate->transition_capture);
-		}
+			/*
+			 * If there are any indexes, update them for all the inserted tuples,
+			 * and run AFTER ROW INSERT triggers.
+			 */
+			if (resultRelInfo->ri_NumIndices > 0)
+			{
+				List	   *recheckIndexes;
+
+				cstate->cur_lineno = buffer->linenos[i];
+				recheckIndexes =
+					ExecInsertIndexTuples(resultRelInfo,
+										  buffer->slots[i], estate, false, false,
+										  NULL, NIL);
+				ExecARInsertTriggers(estate, resultRelInfo,
+									 slots[i], recheckIndexes,
+									 cstate->transition_capture);
+				list_free(recheckIndexes);
+			}
 
-		ExecClearTuple(slots[i]);
+			/*
+			 * There's no indexes, but see if we need to run AFTER ROW INSERT
+			 * triggers anyway.
+			 */
+			else if (resultRelInfo->ri_TrigDesc != NULL &&
+					 (resultRelInfo->ri_TrigDesc->trig_insert_after_row ||
+					  resultRelInfo->ri_TrigDesc->trig_insert_new_table))
+			{
+				cstate->cur_lineno = buffer->linenos[i];
+				ExecARInsertTriggers(estate, resultRelInfo,
+									 slots[i], NIL, cstate->transition_capture);
+			}
+
+			ExecClearTuple(slots[i]);
+		}
 	}
 
 	/* Mark that all slots are free */
@@ -537,12 +547,10 @@ CopyFrom(CopyFromState cstate)
 	CommandId	mycid = GetCurrentCommandId(true);
 	int			ti_options = 0; /* start with default options for insert */
 	BulkInsertState bistate = NULL;
-	CopyInsertMethod insertMethod;
 	CopyMultiInsertInfo multiInsertInfo = {0};	/* pacify compiler */
 	uint64		processed = 0;
 	bool		has_before_insert_row_trig;
 	bool		has_instead_insert_row_trig;
-	bool		leafpart_use_multi_insert = false;
 
 	Assert(cstate->rel);
 	Assert(list_length(cstate->range_table) == 1);
@@ -652,6 +660,33 @@ CopyFrom(CopyFromState cstate)
 	resultRelInfo = target_resultRelInfo = makeNode(ResultRelInfo);
 	ExecInitResultRelation(estate, resultRelInfo, 1);
 
+	Assert(target_resultRelInfo->ri_usesMultiInsert == false);
+
+	/*
+	 * It's generally more efficient to prepare a bunch of tuples for
+	 * insertion, and insert them in bulk, for example, with one
+	 * table_multi_insert() call than call table_tuple_insert() separately for
+	 * every tuple. However, there are a number of reasons why we might not be
+	 * able to do this.  For example, if there any volatile expressions in the
+	 * table's default values or in the statement's WHERE clause, which may
+	 * query the table we are inserting into, buffering tuples might produce
+	 * wrong results.  Also, the relation we are trying to insert into itself
+	 * may not be amenable to buffered inserts.
+	 *
+	 * Note: For partitions, this flag is set considering the target table's
+	 * flag that is being set here and partition's own properties which are
+	 * checked by calling ExecMultiInsertAllowed().  It does not matter
+	 * whether partitions have any volatile default expressions as we use the
+	 * defaults from the target of the COPY command.
+	 * Also, the COPY command requires a non-zero input list of attributes.
+	 * Therefore, the length of the attribute list is checked here.
+	 */
+	if (!cstate->volatile_defexprs &&
+		list_length(cstate->attnumlist) > 0 &&
+		!contain_volatile_functions(cstate->whereClause))
+		target_resultRelInfo->ri_usesMultiInsert =
+					ExecMultiInsertAllowed(target_resultRelInfo, NULL);
+
 	/* Verify the named relation is a valid target for INSERT */
 	CheckValidResultRel(resultRelInfo, CMD_INSERT);
 
@@ -668,10 +703,22 @@ CopyFrom(CopyFromState cstate)
 	mtstate->resultRelInfo = resultRelInfo;
 	mtstate->rootResultRelInfo = resultRelInfo;
 
-	if (resultRelInfo->ri_FdwRoutine != NULL &&
-		resultRelInfo->ri_FdwRoutine->BeginForeignInsert != NULL)
-		resultRelInfo->ri_FdwRoutine->BeginForeignInsert(mtstate,
-														 resultRelInfo);
+	/*
+	 * Init copying process into foreign table. Initialization of copying into
+	 * foreign partitions will be done later.
+	 */
+	if (target_resultRelInfo->ri_FdwRoutine != NULL)
+	{
+		if (target_resultRelInfo->ri_usesMultiInsert &&
+			target_resultRelInfo->ri_FdwRoutine->BeginForeignCopy != NULL)
+		{
+			target_resultRelInfo->ri_FdwRoutine->BeginForeignCopy(mtstate,
+																  resultRelInfo);
+		}
+		else if (target_resultRelInfo->ri_FdwRoutine->BeginForeignInsert != NULL)
+			target_resultRelInfo->ri_FdwRoutine->BeginForeignInsert(mtstate,
+																	resultRelInfo);
+	}
 
 	/* Prepare to catch AFTER triggers. */
 	AfterTriggerBeginQuery();
@@ -700,83 +747,9 @@ CopyFrom(CopyFromState cstate)
 		cstate->qualexpr = ExecInitQual(castNode(List, cstate->whereClause),
 										&mtstate->ps);
 
-	/*
-	 * It's generally more efficient to prepare a bunch of tuples for
-	 * insertion, and insert them in one table_multi_insert() call, than call
-	 * table_tuple_insert() separately for every tuple. However, there are a
-	 * number of reasons why we might not be able to do this.  These are
-	 * explained below.
-	 */
-	if (resultRelInfo->ri_TrigDesc != NULL &&
-		(resultRelInfo->ri_TrigDesc->trig_insert_before_row ||
-		 resultRelInfo->ri_TrigDesc->trig_insert_instead_row))
-	{
-		/*
-		 * Can't support multi-inserts when there are any BEFORE/INSTEAD OF
-		 * triggers on the table. Such triggers might query the table we're
-		 * inserting into and act differently if the tuples that have already
-		 * been processed and prepared for insertion are not there.
-		 */
-		insertMethod = CIM_SINGLE;
-	}
-	else if (proute != NULL && resultRelInfo->ri_TrigDesc != NULL &&
-			 resultRelInfo->ri_TrigDesc->trig_insert_new_table)
-	{
-		/*
-		 * For partitioned tables we can't support multi-inserts when there
-		 * are any statement level insert triggers. It might be possible to
-		 * allow partitioned tables with such triggers in the future, but for
-		 * now, CopyMultiInsertInfoFlush expects that any before row insert
-		 * and statement level insert triggers are on the same relation.
-		 */
-		insertMethod = CIM_SINGLE;
-	}
-	else if (resultRelInfo->ri_FdwRoutine != NULL ||
-			 cstate->volatile_defexprs)
-	{
-		/*
-		 * Can't support multi-inserts to foreign tables or if there are any
-		 * volatile default expressions in the table.  Similarly to the
-		 * trigger case above, such expressions may query the table we're
-		 * inserting into.
-		 *
-		 * Note: It does not matter if any partitions have any volatile
-		 * default expressions as we use the defaults from the target of the
-		 * COPY command.
-		 */
-		insertMethod = CIM_SINGLE;
-	}
-	else if (contain_volatile_functions(cstate->whereClause))
-	{
-		/*
-		 * Can't support multi-inserts if there are any volatile function
-		 * expressions in WHERE clause.  Similarly to the trigger case above,
-		 * such expressions may query the table we're inserting into.
-		 */
-		insertMethod = CIM_SINGLE;
-	}
-	else
-	{
-		/*
-		 * For partitioned tables, we may still be able to perform bulk
-		 * inserts.  However, the possibility of this depends on which types
-		 * of triggers exist on the partition.  We must disable bulk inserts
-		 * if the partition is a foreign table or it has any before row insert
-		 * or insert instead triggers (same as we checked above for the parent
-		 * table).  Since the partition's resultRelInfos are initialized only
-		 * when we actually need to insert the first tuple into them, we must
-		 * have the intermediate insert method of CIM_MULTI_CONDITIONAL to
-		 * flag that we must later determine if we can use bulk-inserts for
-		 * the partition being inserted into.
-		 */
-		if (proute)
-			insertMethod = CIM_MULTI_CONDITIONAL;
-		else
-			insertMethod = CIM_MULTI;
-
+	if (resultRelInfo->ri_usesMultiInsert)
 		CopyMultiInsertInfoInit(&multiInsertInfo, resultRelInfo, cstate,
 								estate, mycid, ti_options);
-	}
 
 	/*
 	 * If not using batch mode (which allocates slots as needed) set up a
@@ -784,7 +757,7 @@ CopyFrom(CopyFromState cstate)
 	 * one, even if we might batch insert, to read the tuple in the root
 	 * partition's form.
 	 */
-	if (insertMethod == CIM_SINGLE || insertMethod == CIM_MULTI_CONDITIONAL)
+	if (!resultRelInfo->ri_usesMultiInsert || proute)
 	{
 		singleslot = table_slot_create(resultRelInfo->ri_RelationDesc,
 									   &estate->es_tupleTable);
@@ -827,7 +800,7 @@ CopyFrom(CopyFromState cstate)
 		ResetPerTupleExprContext(estate);
 
 		/* select slot to (initially) load row into */
-		if (insertMethod == CIM_SINGLE || proute)
+		if (!target_resultRelInfo->ri_usesMultiInsert || proute)
 		{
 			myslot = singleslot;
 			Assert(myslot != NULL);
@@ -835,7 +808,6 @@ CopyFrom(CopyFromState cstate)
 		else
 		{
 			Assert(resultRelInfo == target_resultRelInfo);
-			Assert(insertMethod == CIM_MULTI);
 
 			myslot = CopyMultiInsertInfoNextFreeSlot(&multiInsertInfo,
 													 resultRelInfo);
@@ -894,24 +866,14 @@ CopyFrom(CopyFromState cstate)
 				has_instead_insert_row_trig = (resultRelInfo->ri_TrigDesc &&
 											   resultRelInfo->ri_TrigDesc->trig_insert_instead_row);
 
-				/*
-				 * Disable multi-inserts when the partition has BEFORE/INSTEAD
-				 * OF triggers, or if the partition is a foreign partition.
-				 */
-				leafpart_use_multi_insert = insertMethod == CIM_MULTI_CONDITIONAL &&
-					!has_before_insert_row_trig &&
-					!has_instead_insert_row_trig &&
-					resultRelInfo->ri_FdwRoutine == NULL;
-
 				/* Set the multi-insert buffer to use for this partition. */
-				if (leafpart_use_multi_insert)
+				if (resultRelInfo->ri_usesMultiInsert)
 				{
 					if (resultRelInfo->ri_CopyMultiInsertBuffer == NULL)
 						CopyMultiInsertInfoSetupBuffer(&multiInsertInfo,
 													   resultRelInfo);
 				}
-				else if (insertMethod == CIM_MULTI_CONDITIONAL &&
-						 !CopyMultiInsertInfoIsEmpty(&multiInsertInfo))
+				else if (!CopyMultiInsertInfoIsEmpty(&multiInsertInfo))
 				{
 					/*
 					 * Flush pending inserts if this partition can't use
@@ -941,7 +903,7 @@ CopyFrom(CopyFromState cstate)
 			 * rowtype.
 			 */
 			map = resultRelInfo->ri_RootToPartitionMap;
-			if (insertMethod == CIM_SINGLE || !leafpart_use_multi_insert)
+			if (!resultRelInfo->ri_usesMultiInsert)
 			{
 				/* non batch insert */
 				if (map != NULL)
@@ -960,9 +922,6 @@ CopyFrom(CopyFromState cstate)
 				 */
 				TupleTableSlot *batchslot;
 
-				/* no other path available for partitioned table */
-				Assert(insertMethod == CIM_MULTI_CONDITIONAL);
-
 				batchslot = CopyMultiInsertInfoNextFreeSlot(&multiInsertInfo,
 															resultRelInfo);
 
@@ -1034,7 +993,7 @@ CopyFrom(CopyFromState cstate)
 					ExecPartitionCheck(resultRelInfo, myslot, estate, true);
 
 				/* Store the slot in the multi-insert buffer, when enabled. */
-				if (insertMethod == CIM_MULTI || leafpart_use_multi_insert)
+				if (resultRelInfo->ri_usesMultiInsert)
 				{
 					/*
 					 * The slot previously might point into the per-tuple
@@ -1112,11 +1071,8 @@ CopyFrom(CopyFromState cstate)
 	}
 
 	/* Flush any remaining buffered tuples */
-	if (insertMethod != CIM_SINGLE)
-	{
-		if (!CopyMultiInsertInfoIsEmpty(&multiInsertInfo))
-			CopyMultiInsertInfoFlush(&multiInsertInfo, NULL);
-	}
+	if (!CopyMultiInsertInfoIsEmpty(&multiInsertInfo))
+		CopyMultiInsertInfoFlush(&multiInsertInfo, NULL);
 
 	/* Done, clean up */
 	error_context_stack = errcallback.previous;
@@ -1142,14 +1098,19 @@ CopyFrom(CopyFromState cstate)
 	ExecResetTupleTable(estate->es_tupleTable, false);
 
 	/* Allow the FDW to shut down */
-	if (target_resultRelInfo->ri_FdwRoutine != NULL &&
-		target_resultRelInfo->ri_FdwRoutine->EndForeignInsert != NULL)
-		target_resultRelInfo->ri_FdwRoutine->EndForeignInsert(estate,
-															  target_resultRelInfo);
+	if (target_resultRelInfo->ri_FdwRoutine != NULL)
+	{
+		if (target_resultRelInfo->ri_usesMultiInsert &&
+			target_resultRelInfo->ri_FdwRoutine->EndForeignCopy != NULL)
+			target_resultRelInfo->ri_FdwRoutine->EndForeignCopy(estate,
+														target_resultRelInfo);
+		else if (target_resultRelInfo->ri_FdwRoutine->EndForeignInsert != NULL)
+			target_resultRelInfo->ri_FdwRoutine->EndForeignInsert(estate,
+														target_resultRelInfo);
+	}
 
 	/* Tear down the multi-insert buffer data */
-	if (insertMethod != CIM_SINGLE)
-		CopyMultiInsertInfoCleanup(&multiInsertInfo);
+	CopyMultiInsertInfoCleanup(&multiInsertInfo);
 
 	/* Close all the partitioned tables, leaf partitions, and their indices */
 	if (proute)
diff --git a/src/backend/commands/copyto.c b/src/backend/commands/copyto.c
index e04ec1e..7a10c9d 100644
--- a/src/backend/commands/copyto.c
+++ b/src/backend/commands/copyto.c
@@ -52,6 +52,7 @@ typedef enum CopyDest
 	COPY_FILE,					/* to file (or a piped program) */
 	COPY_OLD_FE,				/* to frontend (2.0 protocol) */
 	COPY_NEW_FE,				/* to frontend (3.0 protocol) */
+	COPY_CALLBACK				/* to callback function */
 } CopyDest;
 
 /*
@@ -82,11 +83,14 @@ typedef struct CopyToStateData
 
 	/* parameters from the COPY command */
 	Relation	rel;			/* relation to copy to */
+	TupleDesc	tupDesc;		/* COPY TO will be used for manual tuple copying
+								  * into the destination */
 	QueryDesc  *queryDesc;		/* executable query to copy from */
 	List	   *attnumlist;		/* integer list of attnums to copy */
 	char	   *filename;		/* filename, or NULL for STDOUT */
 	bool		is_program;		/* is 'filename' a program to popen? */
 
+	copy_data_dest_cb data_dest_cb;	/* function for writing data */
 	CopyFormatOptions opts;
 	Node	   *whereClause;	/* WHERE condition (or NULL) */
 
@@ -117,7 +121,6 @@ static const char BinarySignature[11] = "PGCOPY\n\377\r\n\0";
 static void EndCopy(CopyToState cstate);
 static void ClosePipeToProgram(CopyToState cstate);
 static uint64 CopyTo(CopyToState cstate);
-static void CopyOneRowTo(CopyToState cstate, TupleTableSlot *slot);
 static void CopyAttributeOutText(CopyToState cstate, char *string);
 static void CopyAttributeOutCSV(CopyToState cstate, char *string,
 								bool use_quote, bool single_attr);
@@ -289,6 +292,14 @@ CopySendEndOfRow(CopyToState cstate)
 			/* Dump the accumulated row as one CopyData message */
 			(void) pq_putmessage('d', fe_msgbuf->data, fe_msgbuf->len);
 			break;
+		case COPY_CALLBACK:
+			Assert(!cstate->opts.binary);
+#ifndef WIN32
+			CopySendChar(cstate, '\n');
+#else
+			CopySendString(cstate, "\r\n");
+#endif
+			cstate->data_dest_cb(fe_msgbuf->data, fe_msgbuf->len);
 	}
 
 	/* Update the progress */
@@ -382,19 +393,24 @@ EndCopy(CopyToState cstate)
 CopyToState
 BeginCopyTo(ParseState *pstate,
 			Relation rel,
+			TupleDesc srcTupDesc,
 			RawStmt *raw_query,
 			Oid queryRelId,
 			const char *filename,
 			bool is_program,
+			copy_data_dest_cb data_dest_cb,
 			List *attnamelist,
 			List *options)
 {
 	CopyToState	cstate;
-	bool		pipe = (filename == NULL);
+	bool		pipe = (filename == NULL) && (data_dest_cb == NULL);
 	TupleDesc	tupDesc;
 	int			num_phys_attrs;
 	MemoryContext oldcontext;
 
+	/* Impossible to mix CopyTo modes */
+	Assert(rel == NULL || srcTupDesc == NULL);
+
 	if (rel != NULL && rel->rd_rel->relkind != RELKIND_RELATION)
 	{
 		if (rel->rd_rel->relkind == RELKIND_VIEW)
@@ -459,6 +475,11 @@ BeginCopyTo(ParseState *pstate,
 
 		tupDesc = RelationGetDescr(cstate->rel);
 	}
+	else if (srcTupDesc)
+	{
+		Assert(!raw_query);
+		tupDesc = cstate->tupDesc = srcTupDesc;
+	}
 	else
 	{
 		List	   *rewritten;
@@ -704,6 +725,11 @@ BeginCopyTo(ParseState *pstate,
 		if (whereToSendOutput != DestRemote)
 			cstate->copy_file = stdout;
 	}
+	else if (data_dest_cb)
+	{
+		cstate->copy_dest = COPY_CALLBACK;
+		cstate->data_dest_cb = data_dest_cb;
+	}
 	else
 	{
 		cstate->filename = pstrdup(filename);
@@ -786,7 +812,7 @@ BeginCopyTo(ParseState *pstate,
 uint64
 DoCopyTo(CopyToState cstate)
 {
-	bool		pipe = (cstate->filename == NULL);
+	bool		pipe = (cstate->filename == NULL) && (cstate->data_dest_cb == NULL);
 	bool		fe_copy = (pipe && whereToSendOutput == DestRemote);
 	uint64		processed;
 
@@ -795,7 +821,9 @@ DoCopyTo(CopyToState cstate)
 		if (fe_copy)
 			SendCopyBegin(cstate);
 
+		CopyToStart(cstate);
 		processed = CopyTo(cstate);
+		CopyToFinish(cstate);
 
 		if (fe_copy)
 			SendCopyEnd(cstate);
@@ -835,18 +863,22 @@ EndCopyTo(CopyToState cstate)
 }
 
 /*
- * Copy from relation or query TO file.
+ * Start COPY TO operation.
+ * Separated to the routine to prevent duplicate operations in the case of
+ * manual mode, where tuples are copied to the destination one by one, by call of
+ * the CopyOneRowTo() routine.
  */
-static uint64
-CopyTo(CopyToState cstate)
+void
+CopyToStart(CopyToState cstate)
 {
 	TupleDesc	tupDesc;
 	int			num_phys_attrs;
 	ListCell   *cur;
-	uint64		processed;
 
 	if (cstate->rel)
 		tupDesc = RelationGetDescr(cstate->rel);
+	else if (cstate->tupDesc)
+		tupDesc = cstate->tupDesc;
 	else
 		tupDesc = cstate->queryDesc->tupDesc;
 	num_phys_attrs = tupDesc->natts;
@@ -933,6 +965,32 @@ CopyTo(CopyToState cstate)
 			CopySendEndOfRow(cstate);
 		}
 	}
+}
+
+/*
+ * Finish COPY TO operation.
+ */
+void
+CopyToFinish(CopyToState cstate)
+{
+	if (cstate->opts.binary)
+	{
+		/* Generate trailer for a binary copy */
+		CopySendInt16(cstate, -1);
+		/* Need to flush out the trailer */
+		CopySendEndOfRow(cstate);
+	}
+
+	MemoryContextDelete(cstate->rowcontext);
+}
+
+/*
+ * Copy from relation or query TO file.
+ */
+static uint64
+CopyTo(CopyToState cstate)
+{
+	uint64		processed;
 
 	if (cstate->rel)
 	{
@@ -967,23 +1025,13 @@ CopyTo(CopyToState cstate)
 		processed = ((DR_copy *) cstate->queryDesc->dest)->processed;
 	}
 
-	if (cstate->opts.binary)
-	{
-		/* Generate trailer for a binary copy */
-		CopySendInt16(cstate, -1);
-		/* Need to flush out the trailer */
-		CopySendEndOfRow(cstate);
-	}
-
-	MemoryContextDelete(cstate->rowcontext);
-
 	return processed;
 }
 
 /*
  * Emit one row during CopyTo().
  */
-static void
+void
 CopyOneRowTo(CopyToState cstate, TupleTableSlot *slot)
 {
 	bool		need_delim = false;
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index c74ce36..744ffe7 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -1233,10 +1233,62 @@ InitResultRelInfo(ResultRelInfo *resultRelInfo,
 													 * ExecInitRoutingInfo */
 	resultRelInfo->ri_PartitionTupleSlot = NULL;	/* ditto */
 	resultRelInfo->ri_ChildToRootMap = NULL;
+	resultRelInfo->ri_usesMultiInsert = false;
 	resultRelInfo->ri_CopyMultiInsertBuffer = NULL;
 }
 
 /*
+ * ExecMultiInsertAllowed
+ *		Does this relation allow caller to use multi-insert mode when
+ *		inserting rows into it?
+ */
+bool
+ExecMultiInsertAllowed(const ResultRelInfo *rri,
+							  const ResultRelInfo *partition_root)
+{
+	/*
+	 * If a partition's root parent isn't allowed to use it, neither is the
+	 * partition.
+	 */
+	if (partition_root && !partition_root->ri_usesMultiInsert)
+		return false;
+
+	/*
+	 * Can't support multi-inserts when there are any BEFORE/INSTEAD OF
+	 * triggers on the table. Such triggers might query the table we're
+	 * inserting into and act differently if the tuples that have already
+	 * been processed and prepared for insertion are not there.
+	 */
+	if (rri->ri_TrigDesc != NULL &&
+		(rri->ri_TrigDesc->trig_insert_before_row ||
+		 rri->ri_TrigDesc->trig_insert_instead_row))
+		return false;
+
+	/*
+	 * For partitioned tables we can't support multi-inserts when there are
+	 * any statement level insert triggers. It might be possible to allow
+	 * partitioned tables with such triggers in the future, but for now,
+	 * CopyMultiInsertInfoFlush expects that any before row insert and
+	 * statement level insert triggers are on the same relation.
+	 */
+	if (rri->ri_RelationDesc->rd_rel->relkind == RELKIND_PARTITIONED_TABLE &&
+		rri->ri_TrigDesc != NULL &&
+		rri->ri_TrigDesc->trig_insert_new_table)
+		return false;
+
+	if (rri->ri_FdwRoutine != NULL &&
+		rri->ri_FdwRoutine->ExecForeignCopy == NULL)
+		/*
+		 * Foreign tables don't support multi-inserts, unless their FDW
+		 * provides the necessary COPY interface.
+		 */
+		return false;
+
+	/* OK, caller can use multi-insert on this relation. */
+	return true;
+}
+
+/*
  * ExecGetTriggerResultRel
  *		Get a ResultRelInfo for a trigger target relation.
  *
diff --git a/src/backend/executor/execPartition.c b/src/backend/executor/execPartition.c
index b9e4f2d..76dc31f 100644
--- a/src/backend/executor/execPartition.c
+++ b/src/backend/executor/execPartition.c
@@ -589,6 +589,13 @@ ExecInitPartitionInfo(ModifyTableState *mtstate, EState *estate,
 					  estate->es_instrument);
 
 	/*
+	 * Use multi-insert mode if the condition checking passes for the
+	 * parent and its child.
+	 */
+	leaf_part_rri->ri_usesMultiInsert =
+		ExecMultiInsertAllowed(leaf_part_rri, rootResultRelInfo);
+
+	/*
 	 * Verify result relation is a valid target for an INSERT.  An UPDATE of a
 	 * partition-key becomes a DELETE+INSERT operation, so this check is still
 	 * required when the operation is CMD_UPDATE.
@@ -989,9 +996,16 @@ ExecInitRoutingInfo(ModifyTableState *mtstate,
 	 * If the partition is a foreign table, let the FDW init itself for
 	 * routing tuples to the partition.
 	 */
-	if (partRelInfo->ri_FdwRoutine != NULL &&
-		partRelInfo->ri_FdwRoutine->BeginForeignInsert != NULL)
-		partRelInfo->ri_FdwRoutine->BeginForeignInsert(mtstate, partRelInfo);
+	if (partRelInfo->ri_FdwRoutine != NULL)
+	{
+		if (partRelInfo->ri_usesMultiInsert)
+		{
+			Assert(partRelInfo->ri_FdwRoutine->BeginForeignCopy != NULL);
+			partRelInfo->ri_FdwRoutine->BeginForeignCopy(mtstate, partRelInfo);
+		}
+		else if (partRelInfo->ri_FdwRoutine->BeginForeignInsert != NULL)
+			partRelInfo->ri_FdwRoutine->BeginForeignInsert(mtstate, partRelInfo);
+	}
 
 	/*
 	 * Determine if the FDW supports batch insert and determine the batch
@@ -1210,10 +1224,16 @@ ExecCleanupTupleRouting(ModifyTableState *mtstate,
 		ResultRelInfo *resultRelInfo = proute->partitions[i];
 
 		/* Allow any FDWs to shut down */
-		if (resultRelInfo->ri_FdwRoutine != NULL &&
-			resultRelInfo->ri_FdwRoutine->EndForeignInsert != NULL)
-			resultRelInfo->ri_FdwRoutine->EndForeignInsert(mtstate->ps.state,
-														   resultRelInfo);
+		if (resultRelInfo->ri_FdwRoutine != NULL)
+		{
+			if (resultRelInfo->ri_usesMultiInsert &&
+				resultRelInfo->ri_FdwRoutine->EndForeignCopy != NULL)
+				resultRelInfo->ri_FdwRoutine->EndForeignCopy(mtstate->ps.state,
+															   resultRelInfo);
+			else if (resultRelInfo->ri_FdwRoutine->EndForeignInsert != NULL)
+				resultRelInfo->ri_FdwRoutine->EndForeignInsert(mtstate->ps.state,
+															   resultRelInfo);
+		}
 
 		/*
 		 * Check if this result rel is one belonging to the node's subplans,
diff --git a/src/include/commands/copy.h b/src/include/commands/copy.h
index 8c4748e..a7e7224 100644
--- a/src/include/commands/copy.h
+++ b/src/include/commands/copy.h
@@ -55,6 +55,7 @@ typedef struct CopyFromStateData *CopyFromState;
 typedef struct CopyToStateData *CopyToState;
 
 typedef int (*copy_data_source_cb) (void *outbuf, int minread, int maxread);
+typedef void (*copy_data_dest_cb) (void *outbuf, int len);
 
 extern void DoCopy(ParseState *state, const CopyStmt *stmt,
 				   int stmt_location, int stmt_len,
@@ -78,12 +79,17 @@ extern DestReceiver *CreateCopyDestReceiver(void);
 /*
  * internal prototypes
  */
-extern CopyToState BeginCopyTo(ParseState *pstate, Relation rel, RawStmt *query,
+extern CopyToState BeginCopyTo(ParseState *pstate, Relation rel,
+							   TupleDesc tupDesc, RawStmt *query,
 							   Oid queryRelId, const char *filename, bool is_program,
+							   copy_data_dest_cb data_dest_cb,
 							   List *attnamelist, List *options);
 extern void EndCopyTo(CopyToState cstate);
 extern uint64 DoCopyTo(CopyToState cstate);
 extern List *CopyGetAttnums(TupleDesc tupDesc, Relation rel,
 							List *attnamelist);
+extern void CopyToStart(CopyToState cstate);
+extern void CopyToFinish(CopyToState cstate);
+extern void CopyOneRowTo(CopyToState cstate, TupleTableSlot *slot);
 
 #endif							/* COPY_H */
diff --git a/src/include/commands/copyfrom_internal.h b/src/include/commands/copyfrom_internal.h
index e37942d..c527610 100644
--- a/src/include/commands/copyfrom_internal.h
+++ b/src/include/commands/copyfrom_internal.h
@@ -41,16 +41,6 @@ typedef enum EolType
 } EolType;
 
 /*
- * Represents the heap insert method to be used during COPY FROM.
- */
-typedef enum CopyInsertMethod
-{
-	CIM_SINGLE,					/* use table_tuple_insert or fdw routine */
-	CIM_MULTI,					/* always use table_multi_insert */
-	CIM_MULTI_CONDITIONAL		/* use table_multi_insert only if valid */
-} CopyInsertMethod;
-
-/*
  * This struct contains all the state variables used throughout a COPY FROM
  * operation.
  *
diff --git a/src/include/executor/execPartition.h b/src/include/executor/execPartition.h
index d30ffde..b5f73d8 100644
--- a/src/include/executor/execPartition.h
+++ b/src/include/executor/execPartition.h
@@ -118,6 +118,8 @@ extern ResultRelInfo *ExecFindPartition(ModifyTableState *mtstate,
 										PartitionTupleRouting *proute,
 										TupleTableSlot *slot,
 										EState *estate);
+extern bool checkMultiInsertMode(const ResultRelInfo *rri,
+								 const ResultRelInfo *parent);
 extern void ExecCleanupTupleRouting(ModifyTableState *mtstate,
 									PartitionTupleRouting *proute);
 extern PartitionPruneState *ExecCreatePartitionPruneState(PlanState *planstate,
diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index 071e363..fe3aab5 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -193,6 +193,8 @@ extern void InitResultRelInfo(ResultRelInfo *resultRelInfo,
 							  Index resultRelationIndex,
 							  ResultRelInfo *partition_root_rri,
 							  int instrument_options);
+extern bool ExecMultiInsertAllowed(const ResultRelInfo *rri,
+										  const ResultRelInfo *partition_root);
 extern ResultRelInfo *ExecGetTriggerResultRel(EState *estate, Oid relid);
 extern void ExecConstraints(ResultRelInfo *resultRelInfo,
 							TupleTableSlot *slot, EState *estate);
diff --git a/src/include/foreign/fdwapi.h b/src/include/foreign/fdwapi.h
index 248f78d..676a1b7 100644
--- a/src/include/foreign/fdwapi.h
+++ b/src/include/foreign/fdwapi.h
@@ -126,6 +126,16 @@ typedef TupleTableSlot *(*IterateDirectModify_function) (ForeignScanState *node)
 
 typedef void (*EndDirectModify_function) (ForeignScanState *node);
 
+typedef void (*BeginForeignCopy_function) (ModifyTableState *mtstate,
+										   ResultRelInfo *rinfo);
+
+typedef void (*ExecForeignCopy_function) (ResultRelInfo *rinfo,
+										  TupleTableSlot **slots,
+										  int nslots);
+
+typedef void (*EndForeignCopy_function) (EState *estate,
+										 ResultRelInfo *rinfo);
+
 typedef RowMarkType (*GetForeignRowMarkType_function) (RangeTblEntry *rte,
 													   LockClauseStrength strength);
 
@@ -230,6 +240,11 @@ typedef struct FdwRoutine
 	IterateDirectModify_function IterateDirectModify;
 	EndDirectModify_function EndDirectModify;
 
+	/* Support functions for COPY into foreign tables */
+	BeginForeignCopy_function BeginForeignCopy;
+	ExecForeignCopy_function ExecForeignCopy;
+	EndForeignCopy_function EndForeignCopy;
+
 	/* Functions for SELECT FOR UPDATE/SHARE row locking */
 	GetForeignRowMarkType_function GetForeignRowMarkType;
 	RefetchForeignRow_function RefetchForeignRow;
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index b6a88ff..4ec5b34 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -508,7 +508,13 @@ typedef struct ResultRelInfo
 	 */
 	TupleConversionMap *ri_ChildToRootMap;
 
-	/* for use by copyfrom.c when performing multi-inserts */
+	/*
+	 * The following fields are currently only relevant to copyfrom.c.
+	 * True if okay to use multi-insert on this relation
+	 */
+	bool ri_usesMultiInsert;
+
+	/* Buffer allocated to this relation when using multi-insert mode */
 	struct CopyMultiInsertBuffer *ri_CopyMultiInsertBuffer;
 } ResultRelInfo;
 
-- 
2.10.1

