MERGE SQL Command following SQL:2016

MERGE performs actions that modify rows in the target table
using a source table or query. MERGE provides a single SQL
statement that can conditionally INSERT/UPDATE/DELETE rows
a task that would other require multiple PL statements.
e.g.

MERGE INTO target AS t
USING source AS s
ON t.tid = s.sid
WHEN MATCHED AND t.balance > s.delta THEN
  UPDATE SET balance = t.balance - s.delta
WHEN MATCHED THEN
  DELETE
WHEN NOT MATCHED AND s.delta > 0 THEN
  INSERT VALUES (s.sid, s.delta)
WHEN NOT MATCHED THEN
  DO NOTHING;

MERGE works with regular and partitioned tables, including
column and row security enforcement, as well as support for
row, statement and transition triggers.

MERGE is optimized for OLTP and is parameterizable, though
also useful for large scale ETL/ELT. MERGE is not intended
to be used in preference to existing single SQL commands
for INSERT, UPDATE or DELETE since there is some overhead.
MERGE can be used statically from PL/pgSQL.

MERGE does not yet support inheritance, write rules,
RETURNING clauses, updatable views or foreign tables.
MERGE follows SQL Standard per the most recent SQL:2016.

Includes full tests and documentation, including full
isolation tests to demonstrate the concurrent behavior.

This version written from scratch in 2017 by Simon Riggs,
using docs and tests originally written in 2009. Later work
from Pavan Deolasee has been both complex and deep, leaving
the lead author credit now in his hands.
Extensive discussion of concurrency from Peter Geoghegan,
with thanks for the time and effort contributed.

Various issues reported via sqlsmith by Andreas Seltenreich

Authors: Pavan Deolasee, Simon Riggs
Reviewer: Peter Geoghegan, Amit Langote, Tomas Vondra, Simon Riggs

Discussion:
https://postgr.es/m/CANP8+jKitBSrB7oTgT9CY2i1ObfOt36z0XMraQc+Xrz8QB0nXA@mail.gmail.com
https://postgr.es/m/CAH2-WzkJdBuxj9PO=2QaO9-3h3xGbQPZ34kJH=HukRekwM-GZg@mail.gmail.com

4 files changed, 28 insertions, 2 deletions

diff --git a/src/include/executor/execPartition.h b/src/include/executor/execPartition.h
index 03a599ad57a..9f55f6409ef 100644
--- a/src/include/executor/execPartition.h
+++ b/src/include/executor/execPartition.h
@@ -114,6 +114,7 @@ extern int ExecFindPartition(ResultRelInfo *resultRelInfo,
 				  PartitionDispatch *pd,
 				  TupleTableSlot *slot,
 				  EState *estate);
+extern int ExecFindPartitionByOid(PartitionTupleRouting *proute, Oid partoid);
 extern ResultRelInfo *ExecInitPartitionInfo(ModifyTableState *mtstate,
 					ResultRelInfo *resultRelInfo,
 					PartitionTupleRouting *proute,
diff --git a/src/include/executor/instrument.h b/src/include/executor/instrument.h
index b72f91898ad..28eb0093d47 100644
--- a/src/include/executor/instrument.h
+++ b/src/include/executor/instrument.h
@@ -58,8 +58,11 @@ typedef struct Instrumentation
 	double		total;			/* Total total time (in seconds) */
 	double		ntuples;		/* Total tuples produced */
 	double		nloops;			/* # of run cycles for this node */
-	double		nfiltered1;		/* # tuples removed by scanqual or joinqual */
-	double		nfiltered2;		/* # tuples removed by "other" quals */
+	double		nfiltered1;		/* # tuples removed by scanqual or joinqual OR
+								 * # tuples inserted by MERGE */
+	double		nfiltered2;		/* # tuples removed by "other" quals OR
+								 * # tuples updated by MERGE */
+	double		nfiltered3;		/* # tuples deleted by MERGE */
 	BufferUsage bufusage;		/* Total buffer usage */
 } Instrumentation;
 
diff --git a/src/include/executor/nodeModifyTable.h b/src/include/executor/nodeModifyTable.h
index 0d7e579e1cb..686cfa61710 100644
--- a/src/include/executor/nodeModifyTable.h
+++ b/src/include/executor/nodeModifyTable.h
@@ -18,5 +18,26 @@
 extern ModifyTableState *ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags);
 extern void ExecEndModifyTable(ModifyTableState *node);
 extern void ExecReScanModifyTable(ModifyTableState *node);
+extern TupleTableSlot *ExecPrepareTupleRouting(ModifyTableState *mtstate,
+						EState *estate,
+						struct PartitionTupleRouting *proute,
+						ResultRelInfo *targetRelInfo,
+						TupleTableSlot *slot);
+extern TupleTableSlot *ExecDelete(ModifyTableState *mtstate,
+		   ItemPointer tupleid, HeapTuple oldtuple, TupleTableSlot *planSlot,
+		   EPQState *epqstate, EState *estate, bool *tupleDeleted,
+		   bool processReturning, HeapUpdateFailureData *hufdp,
+		   MergeActionState *actionState, bool canSetTag);
+extern TupleTableSlot *ExecUpdate(ModifyTableState *mtstate,
+		   ItemPointer tupleid, HeapTuple oldtuple, TupleTableSlot *slot,
+		   TupleTableSlot *planSlot, EPQState *epqstate, EState *estate,
+		   bool *tuple_updated, HeapUpdateFailureData *hufdp,
+		   MergeActionState *actionState, bool canSetTag);
+extern TupleTableSlot *ExecInsert(ModifyTableState *mtstate,
+		   TupleTableSlot *slot,
+		   TupleTableSlot *planSlot,
+		   EState *estate,
+		   MergeActionState *actionState,
+		   bool canSetTag);
 
 #endif							/* NODEMODIFYTABLE_H */
diff --git a/src/include/executor/spi.h b/src/include/executor/spi.h
index e5bdaecc4e3..78410b9f772 100644
--- a/src/include/executor/spi.h
+++ b/src/include/executor/spi.h
@@ -64,6 +64,7 @@ typedef struct _SPI_plan *SPIPlanPtr;
 #define SPI_OK_REL_REGISTER		15
 #define SPI_OK_REL_UNREGISTER	16
 #define SPI_OK_TD_REGISTER		17
+#define SPI_OK_MERGE			18
 
 #define SPI_OPT_NONATOMIC		(1 << 0)