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

src/include/access/heapam.h

@@ -53,23 +53,34 @@ typedef enum LockTupleMode
  * When heap_update, heap_delete, or heap_lock_tuple fail because the target
  * tuple is already outdated, they fill in this struct to provide information
  * to the caller about what happened.
+ *
+ * result is the result of HeapTupleSatisfiesUpdate, leading to the failure.
+ * It's set to HeapTupleMayBeUpdated when there is no failure.
+ *
  * ctid is the target's ctid link: it is the same as the target's TID if the
  * target was deleted, or the location of the replacement tuple if the target
  * was updated.
+ *
  * xmax is the outdating transaction's XID.  If the caller wants to visit the
  * replacement tuple, it must check that this matches before believing the
  * replacement is really a match.
+ *
  * cmax is the outdating command's CID, but only when the failure code is
  * HeapTupleSelfUpdated (i.e., something in the current transaction outdated
  * the tuple); otherwise cmax is zero.  (We make this restriction because
  * HeapTupleHeaderGetCmax doesn't work for tuples outdated in other
  * transactions.)
+ *
+ * lockmode is only relevant for callers of heap_update() and is the mode which
+ * the caller should use in case it needs to lock the updated tuple.
  */
 typedef struct HeapUpdateFailureData
 {
+	HTSU_Result result;
 	ItemPointerData ctid;
 	TransactionId xmax;
 	CommandId	cmax;
+	LockTupleMode	lockmode;
 } HeapUpdateFailureData;
 
 
@@ -162,7 +173,7 @@ extern void heap_abort_speculative(Relation relation, HeapTuple tuple);
 extern HTSU_Result heap_update(Relation relation, ItemPointer otid,
 			HeapTuple newtup,
 			CommandId cid, Snapshot crosscheck, bool wait,
-			HeapUpdateFailureData *hufd, LockTupleMode *lockmode);
+			HeapUpdateFailureData *hufd);
 extern HTSU_Result heap_lock_tuple(Relation relation, HeapTuple tuple,
 				CommandId cid, LockTupleMode mode, LockWaitPolicy wait_policy,
 				bool follow_update,

src/include/commands/trigger.h

@@ -206,7 +206,8 @@ extern bool ExecBRDeleteTriggers(EState *estate,
 					 EPQState *epqstate,
 					 ResultRelInfo *relinfo,
 					 ItemPointer tupleid,
-					 HeapTuple fdw_trigtuple);
+					 HeapTuple fdw_trigtuple,
+					 HeapUpdateFailureData *hufdp);
 extern void ExecARDeleteTriggers(EState *estate,
 					 ResultRelInfo *relinfo,
 					 ItemPointer tupleid,
@@ -225,7 +226,8 @@ extern TupleTableSlot *ExecBRUpdateTriggers(EState *estate,
 					 ResultRelInfo *relinfo,
 					 ItemPointer tupleid,
 					 HeapTuple fdw_trigtuple,
-					 TupleTableSlot *slot);
+					 TupleTableSlot *slot,
+					 HeapUpdateFailureData *hufdp);
 extern void ExecARUpdateTriggers(EState *estate,
 					 ResultRelInfo *relinfo,
 					 ItemPointer tupleid,

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,

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;
 

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 */

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)
 

src/include/nodes/execnodes.h

@@ -360,8 +360,17 @@ typedef struct JunkFilter
 	AttrNumber *jf_cleanMap;
 	TupleTableSlot *jf_resultSlot;
 	AttrNumber	jf_junkAttNo;
+	AttrNumber	jf_otherJunkAttNo;
 } JunkFilter;
 
+typedef struct MergeState
+{
+	/* List of MERGE MATCHED action states */
+	List		   *matchedActionStates;
+	/* List of MERGE NOT MATCHED action states */
+	List		   *notMatchedActionStates;
+} MergeState;
+
 /*
  * OnConflictSetState
  *
@@ -452,8 +461,38 @@ typedef struct ResultRelInfo
 
 	/* relation descriptor for root partitioned table */
 	Relation	ri_PartitionRoot;
+
+	int			ri_PartitionLeafIndex;
+	/* for running MERGE on this result relation */
+	MergeState *ri_mergeState;
+
+	/*
+	 * While executing MERGE, the target relation is processed twice; once
+	 * as a target relation and once to run a join between the target and the
+	 * source. We generate two different RTEs for these two purposes, one with
+	 * rte->inh set to false and other with rte->inh set to true.
+	 *
+	 * Since the plan re-evaluated by EvalPlanQual uses the join RTE, we must
+	 * install the updated tuple in the scan corresponding to that RTE. The
+	 * following member tracks the index of the second RTE for EvalPlanQual
+	 * purposes. ri_mergeTargetRTI is non-zero only when MERGE is in-progress.
+	 * We use ri_mergeTargetRTI to run EvalPlanQual for MERGE and
+	 * ri_RangeTableIndex elsewhere.
+	 */
+	Index		ri_mergeTargetRTI;
 } ResultRelInfo;
 
+/*
+ * Get the Range table index for EvalPlanQual.
+ *
+ * We use the ri_mergeTargetRTI if set, otherwise use ri_RangeTableIndex.
+ * ri_mergeTargetRTI should really be ever set iff we're running MERGE.
+ */
+#define GetEPQRangeTableIndex(r) \
+	(((r)->ri_mergeTargetRTI > 0)  \
+	 ? (r)->ri_mergeTargetRTI \
+	 : (r)->ri_RangeTableIndex)
+
 /* ----------------
  *	  EState information
  *
@@ -966,6 +1005,11 @@ typedef struct PlanState
 		if (((PlanState *)(node))->instrument) \
 			((PlanState *)(node))->instrument->nfiltered2 += (delta); \
 	} while(0)
+#define InstrCountFiltered3(node, delta) \
+	do { \
+		if (((PlanState *)(node))->instrument) \
+			((PlanState *)(node))->instrument->nfiltered3 += (delta); \
+	} while(0)
 
 /*
  * EPQState is state for executing an EvalPlanQual recheck on a candidate
@@ -1012,6 +1056,20 @@ typedef struct ProjectSetState
 	MemoryContext argcontext;	/* context for SRF arguments */
 } ProjectSetState;
 
+/* ----------------
+ *	 MergeActionState information
+ * ----------------
+ */
+typedef struct MergeActionState
+{
+	NodeTag		type;
+	bool		matched;		/* true=MATCHED, false=NOT MATCHED */
+	ExprState  *whenqual;		/* WHEN AND conditions */
+	CmdType		commandType;	/* INSERT/UPDATE/DELETE/DO NOTHING */
+	ProjectionInfo *proj;		/* tuple projection info */
+	TupleDesc	tupDesc;		/* tuple descriptor for projection */
+} MergeActionState;
+
 /* ----------------
  *	 ModifyTableState information
  * ----------------
@@ -1019,7 +1077,7 @@ typedef struct ProjectSetState
 typedef struct ModifyTableState
 {
 	PlanState	ps;				/* its first field is NodeTag */
-	CmdType		operation;		/* INSERT, UPDATE, or DELETE */
+	CmdType		operation;		/* INSERT, UPDATE, DELETE or MERGE */
 	bool		canSetTag;		/* do we set the command tag/es_processed? */
 	bool		mt_done;		/* are we done? */
 	PlanState **mt_plans;		/* subplans (one per target rel) */
@@ -1035,6 +1093,8 @@ typedef struct ModifyTableState
 	List	   *mt_excludedtlist;	/* the excluded pseudo relation's tlist  */
 	TupleTableSlot *mt_conflproj;	/* CONFLICT ... SET ... projection target */
 
+	TupleTableSlot *mt_mergeproj;	/* MERGE action projection target */
+
 	/* Tuple-routing support info */
 	struct PartitionTupleRouting *mt_partition_tuple_routing;
 
@@ -1046,6 +1106,9 @@ typedef struct ModifyTableState
 
 	/* Per plan map for tuple conversion from child to root */
 	TupleConversionMap **mt_per_subplan_tupconv_maps;
+
+	/* Flags showing which subcommands are present INS/UPD/DEL/DO NOTHING */
+	int			mt_merge_subcommands;
 } ModifyTableState;
 
 /* ----------------

src/include/nodes/nodes.h

@@ -97,6 +97,7 @@ typedef enum NodeTag
 	T_PlanState,
 	T_ResultState,
 	T_ProjectSetState,
+	T_MergeActionState,
 	T_ModifyTableState,
 	T_AppendState,
 	T_MergeAppendState,
@@ -308,6 +309,8 @@ typedef enum NodeTag
 	T_InsertStmt,
 	T_DeleteStmt,
 	T_UpdateStmt,
+	T_MergeStmt,
+	T_MergeAction,
 	T_SelectStmt,
 	T_AlterTableStmt,
 	T_AlterTableCmd,
@@ -657,7 +660,8 @@ typedef enum CmdType
 	CMD_SELECT,					/* select stmt */
 	CMD_UPDATE,					/* update stmt */
 	CMD_INSERT,					/* insert stmt */
-	CMD_DELETE,
+	CMD_DELETE,					/* delete stmt */
+	CMD_MERGE,					/* merge stmt */
 	CMD_UTILITY,				/* cmds like create, destroy, copy, vacuum,
 								 * etc. */
 	CMD_NOTHING					/* dummy command for instead nothing rules

src/include/nodes/parsenodes.h

@@ -38,7 +38,7 @@ typedef enum OverridingKind
 typedef enum QuerySource
 {
 	QSRC_ORIGINAL,				/* original parsetree (explicit query) */
-	QSRC_PARSER,				/* added by parse analysis (now unused) */
+	QSRC_PARSER,				/* added by parse analysis in MERGE */
 	QSRC_INSTEAD_RULE,			/* added by unconditional INSTEAD rule */
 	QSRC_QUAL_INSTEAD_RULE,		/* added by conditional INSTEAD rule */
 	QSRC_NON_INSTEAD_RULE		/* added by non-INSTEAD rule */
@@ -107,7 +107,7 @@ typedef struct Query
 {
 	NodeTag		type;
 
-	CmdType		commandType;	/* select|insert|update|delete|utility */
+	CmdType		commandType;	/* select|insert|update|delete|merge|utility */
 
 	QuerySource querySource;	/* where did I come from? */
 
@@ -118,7 +118,7 @@ typedef struct Query
 	Node	   *utilityStmt;	/* non-null if commandType == CMD_UTILITY */
 
 	int			resultRelation; /* rtable index of target relation for
-								 * INSERT/UPDATE/DELETE; 0 for SELECT */
+								 * INSERT/UPDATE/DELETE/MERGE; 0 for SELECT */
 
 	bool		hasAggs;		/* has aggregates in tlist or havingQual */
 	bool		hasWindowFuncs; /* has window functions in tlist */
@@ -169,6 +169,9 @@ typedef struct Query
 	List	   *withCheckOptions;	/* a list of WithCheckOption's, which are
 									 * only added during rewrite and therefore
 									 * are not written out as part of Query. */
+	int			mergeTarget_relation;
+	List	   *mergeSourceTargetList;
+	List	   *mergeActionList;	/* list of actions for MERGE (only) */
 
 	/*
 	 * The following two fields identify the portion of the source text string
@@ -1128,7 +1131,9 @@ typedef enum WCOKind
 	WCO_VIEW_CHECK,				/* WCO on an auto-updatable view */
 	WCO_RLS_INSERT_CHECK,		/* RLS INSERT WITH CHECK policy */
 	WCO_RLS_UPDATE_CHECK,		/* RLS UPDATE WITH CHECK policy */
-	WCO_RLS_CONFLICT_CHECK		/* RLS ON CONFLICT DO UPDATE USING policy */
+	WCO_RLS_CONFLICT_CHECK,		/* RLS ON CONFLICT DO UPDATE USING policy */
+	WCO_RLS_MERGE_UPDATE_CHECK, /* RLS MERGE UPDATE USING policy */
+	WCO_RLS_MERGE_DELETE_CHECK	/* RLS MERGE DELETE USING policy */
 } WCOKind;
 
 typedef struct WithCheckOption
@@ -1503,6 +1508,30 @@ typedef struct UpdateStmt
 	WithClause *withClause;		/* WITH clause */
 } UpdateStmt;
 
+/* ----------------------
+ *		Merge Statement
+ * ----------------------
+ */
+typedef struct MergeStmt
+{
+	NodeTag		type;
+	RangeVar   *relation;			/* target relation to merge into */
+	Node	   *source_relation;	/* source relation */
+	Node	   *join_condition; /* join condition between source and target */
+	List	   *mergeActionList;	/* list of MergeAction(s) */
+} MergeStmt;
+
+typedef struct MergeAction
+{
+	NodeTag		type;
+	bool		matched;		/* true=MATCHED, false=NOT MATCHED */
+	Node	   *condition;		/* WHEN AND conditions (raw parser) */
+	Node	   *qual;			/* transformed WHEN AND conditions */
+	CmdType		commandType;	/* INSERT/UPDATE/DELETE/DO NOTHING */
+	Node	   *stmt;			/* T_UpdateStmt etc */
+	List	   *targetList;		/* the target list (of ResTarget) */
+} MergeAction;
+
 /* ----------------------
  *		Select Statement
  *

src/include/nodes/plannodes.h

@@ -18,6 +18,7 @@
 #include "lib/stringinfo.h"
 #include "nodes/bitmapset.h"
 #include "nodes/lockoptions.h"
+#include "nodes/parsenodes.h"
 #include "nodes/primnodes.h"
 
 
@@ -42,7 +43,7 @@ typedef struct PlannedStmt
 {
 	NodeTag		type;
 
-	CmdType		commandType;	/* select|insert|update|delete|utility */
+	CmdType		commandType;	/* select|insert|update|delete|merge|utility */
 
 	uint64		queryId;		/* query identifier (copied from Query) */
 
@@ -216,13 +217,14 @@ typedef struct ProjectSet
 typedef struct ModifyTable
 {
 	Plan		plan;
-	CmdType		operation;		/* INSERT, UPDATE, or DELETE */
+	CmdType		operation;		/* INSERT, UPDATE, DELETE or MERGE */
 	bool		canSetTag;		/* do we set the command tag/es_processed? */
 	Index		nominalRelation;	/* Parent RT index for use of EXPLAIN */
 	/* RT indexes of non-leaf tables in a partition tree */
 	List	   *partitioned_rels;
 	bool		partColsUpdated;	/* some part key in hierarchy updated */
 	List	   *resultRelations;	/* integer list of RT indexes */
+	Index	    mergeTargetRelation;	/* RT index of the merge target */
 	int			resultRelIndex; /* index of first resultRel in plan's list */
 	int			rootResultRelIndex; /* index of the partitioned table root */
 	List	   *plans;			/* plan(s) producing source data */
@@ -238,6 +240,8 @@ typedef struct ModifyTable
 	Node	   *onConflictWhere;	/* WHERE for ON CONFLICT UPDATE */
 	Index		exclRelRTI;		/* RTI of the EXCLUDED pseudo relation */
 	List	   *exclRelTlist;	/* tlist of the EXCLUDED pseudo relation */
+	List	   *mergeSourceTargetList;
+	List	   *mergeActionList;	/* actions for MERGE */
 } ModifyTable;
 
 /* ----------------

src/include/nodes/relation.h

@@ -1670,7 +1670,7 @@ typedef struct LockRowsPath
 } LockRowsPath;
 
 /*
- * ModifyTablePath represents performing INSERT/UPDATE/DELETE modifications
+ * ModifyTablePath represents performing INSERT/UPDATE/DELETE/MERGE
  *
  * We represent most things that will be in the ModifyTable plan node
  * literally, except we have child Path(s) not Plan(s).  But analysis of the
@@ -1679,13 +1679,14 @@ typedef struct LockRowsPath
 typedef struct ModifyTablePath
 {
 	Path		path;
-	CmdType		operation;		/* INSERT, UPDATE, or DELETE */
+	CmdType		operation;		/* INSERT, UPDATE, DELETE or MERGE */
 	bool		canSetTag;		/* do we set the command tag/es_processed? */
 	Index		nominalRelation;	/* Parent RT index for use of EXPLAIN */
 	/* RT indexes of non-leaf tables in a partition tree */
 	List	   *partitioned_rels;
 	bool		partColsUpdated;	/* some part key in hierarchy updated */
 	List	   *resultRelations;	/* integer list of RT indexes */
+	Index	  	mergeTargetRelation;/* RT index of merge target relation */
 	List	   *subpaths;		/* Path(s) producing source data */
 	List	   *subroots;		/* per-target-table PlannerInfos */
 	List	   *withCheckOptionLists;	/* per-target-table WCO lists */
@@ -1693,6 +1694,8 @@ typedef struct ModifyTablePath
 	List	   *rowMarks;		/* PlanRowMarks (non-locking only) */
 	OnConflictExpr *onconflict; /* ON CONFLICT clause, or NULL */
 	int			epqParam;		/* ID of Param for EvalPlanQual re-eval */
+	List	   *mergeSourceTargetList;
+	List	   *mergeActionList;	/* actions for MERGE */
 } ModifyTablePath;
 
 /*

src/include/optimizer/pathnode.h

@@ -241,11 +241,14 @@ extern ModifyTablePath *create_modifytable_path(PlannerInfo *root,
 						CmdType operation, bool canSetTag,
 						Index nominalRelation, List *partitioned_rels,
 						bool partColsUpdated,
-						List *resultRelations, List *subpaths,
+						List *resultRelations,
+						Index	mergeTargetRelation,
+						List *subpaths,
 						List *subroots,
 						List *withCheckOptionLists, List *returningLists,
 						List *rowMarks, OnConflictExpr *onconflict,
-						int epqParam);
+						List *mergeSourceTargetList,
+						List *mergeActionList, int epqParam);
 extern LimitPath *create_limit_path(PlannerInfo *root, RelOptInfo *rel,
 				  Path *subpath,
 				  Node *limitOffset, Node *limitCount,

src/include/parser/analyze.h

@@ -32,6 +32,11 @@ extern Query *parse_sub_analyze(Node *parseTree, ParseState *parentParseState,
 				  bool locked_from_parent,
 				  bool resolve_unknowns);
 
+extern List *transformInsertRow(ParseState *pstate, List *exprlist,
+				   List *stmtcols, List *icolumns, List *attrnos,
+				   bool strip_indirection);
+extern List *transformUpdateTargetList(ParseState *pstate,
+						  List *targetList);
 extern Query *transformTopLevelStmt(ParseState *pstate, RawStmt *parseTree);
 extern Query *transformStmt(ParseState *pstate, Node *parseTree);
 

src/include/parser/kwlist.h

@@ -244,8 +244,10 @@ PG_KEYWORD("locked", LOCKED, UNRESERVED_KEYWORD)
 PG_KEYWORD("logged", LOGGED, UNRESERVED_KEYWORD)
 PG_KEYWORD("mapping", MAPPING, UNRESERVED_KEYWORD)
 PG_KEYWORD("match", MATCH, UNRESERVED_KEYWORD)
+PG_KEYWORD("matched", MATCHED, UNRESERVED_KEYWORD)
 PG_KEYWORD("materialized", MATERIALIZED, UNRESERVED_KEYWORD)
 PG_KEYWORD("maxvalue", MAXVALUE, UNRESERVED_KEYWORD)
+PG_KEYWORD("merge", MERGE, UNRESERVED_KEYWORD)
 PG_KEYWORD("method", METHOD, UNRESERVED_KEYWORD)
 PG_KEYWORD("minute", MINUTE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("minvalue", MINVALUE, UNRESERVED_KEYWORD)

src/include/parser/parse_clause.h

@@ -20,7 +20,10 @@ extern void transformFromClause(ParseState *pstate, List *frmList);
 extern int setTargetTable(ParseState *pstate, RangeVar *relation,
 			   bool inh, bool alsoSource, AclMode requiredPerms);
 extern bool interpretOidsOption(List *defList, bool allowOids);
-
+extern Node *transformFromClauseItem(ParseState *pstate, Node *n,
+						RangeTblEntry **top_rte, int *top_rti,
+						RangeTblEntry **right_rte, int *right_rti,
+						List **namespace);
 extern Node *transformWhereClause(ParseState *pstate, Node *clause,
 					 ParseExprKind exprKind, const char *constructName);
 extern Node *transformLimitClause(ParseState *pstate, Node *clause,

src/include/parser/parse_node.h

@@ -50,6 +50,7 @@ typedef enum ParseExprKind
 	EXPR_KIND_INSERT_TARGET,	/* INSERT target list item */
 	EXPR_KIND_UPDATE_SOURCE,	/* UPDATE assignment source item */
 	EXPR_KIND_UPDATE_TARGET,	/* UPDATE assignment target item */
+	EXPR_KIND_MERGE_WHEN_AND,	/* MERGE WHEN ... AND condition */
 	EXPR_KIND_GROUP_BY,			/* GROUP BY */
 	EXPR_KIND_ORDER_BY,			/* ORDER BY */
 	EXPR_KIND_DISTINCT_ON,		/* DISTINCT ON */
@@ -127,7 +128,7 @@ typedef Node *(*CoerceParamHook) (ParseState *pstate, Param *param,
  * p_parent_cte: CommonTableExpr that immediately contains the current query,
  * if any.
  *
- * p_target_relation: target relation, if query is INSERT, UPDATE, or DELETE.
+ * p_target_relation: target relation, if query is INSERT/UPDATE/DELETE/MERGE
  *
  * p_target_rangetblentry: target relation's entry in the rtable list.
  *
@@ -181,7 +182,7 @@ struct ParseState
 	List	   *p_ctenamespace; /* current namespace for common table exprs */
 	List	   *p_future_ctes;	/* common table exprs not yet in namespace */
 	CommonTableExpr *p_parent_cte;	/* this query's containing CTE */
-	Relation	p_target_relation;	/* INSERT/UPDATE/DELETE target rel */
+	Relation	p_target_relation;	/* INSERT/UPDATE/DELETE/MERGE target rel */
 	RangeTblEntry *p_target_rangetblentry;	/* target rel's RTE */
 	bool		p_is_insert;	/* process assignment like INSERT not UPDATE */
 	List	   *p_windowdefs;	/* raw representations of window clauses */

src/include/rewrite/rewriteHandler.h

@@ -25,6 +25,7 @@ extern void AcquireRewriteLocks(Query *parsetree,
 extern Node *build_column_default(Relation rel, int attrno);
 extern void rewriteTargetListUD(Query *parsetree, RangeTblEntry *target_rte,
 					Relation target_relation);
+extern void rewriteTargetListMerge(Query *parsetree, Relation target_relation);
 
 extern Query *get_view_query(Relation view);
 extern const char *view_query_is_auto_updatable(Query *viewquery,