9 files changed, 34 insertions, 3 deletions
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index b077c0f0f59..7830c02021a 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202004071
+#define CATALOG_VERSION_NO	202004072
 
 #endif
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index fb490b404ce..4c009b1a7c5 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -2449,6 +2449,7 @@ typedef enum
 	LIMIT_RESCAN,				/* rescan after recomputing parameters */
 	LIMIT_EMPTY,				/* there are no returnable rows */
 	LIMIT_INWINDOW,				/* have returned a row in the window */
+	LIMIT_WINDOWEND_TIES,		/* have returned a tied row */
 	LIMIT_SUBPLANEOF,			/* at EOF of subplan (within window) */
 	LIMIT_WINDOWEND,			/* stepped off end of window */
 	LIMIT_WINDOWSTART			/* stepped off beginning of window */
@@ -2459,12 +2460,16 @@ typedef struct LimitState
 	PlanState	ps;				/* its first field is NodeTag */
 	ExprState  *limitOffset;	/* OFFSET parameter, or NULL if none */
 	ExprState  *limitCount;		/* COUNT parameter, or NULL if none */
+	LimitOption limitOption;	/* limit specification type */
 	int64		offset;			/* current OFFSET value */
 	int64		count;			/* current COUNT, if any */
 	bool		noCount;		/* if true, ignore count */
 	LimitStateCond lstate;		/* state machine status, as above */
 	int64		position;		/* 1-based index of last tuple returned */
 	TupleTableSlot *subSlot;	/* tuple last obtained from subplan */
+	ExprState  *eqfunction;		/* tuple equality qual in case of WITH TIES
+								 * option */
+	TupleTableSlot *last_slot;	/* slot for evaluation of ties */
 } LimitState;
 
 #endif							/* EXECNODES_H */
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index 50b1ba51863..381d84b4e4f 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -826,4 +826,17 @@ typedef enum OnConflictAction
 	ONCONFLICT_UPDATE			/* ON CONFLICT ... DO UPDATE */
 } OnConflictAction;
 
+/*
+ * LimitOption -
+ *	LIMIT option of query
+ *
+ * This is needed in both parsenodes.h and plannodes.h, so put it here...
+ */
+typedef enum LimitOption
+{
+	LIMIT_OPTION_COUNT,			/* FETCH FIRST... ONLY */
+	LIMIT_OPTION_WITH_TIES,		/* FETCH FIRST... WITH TIES */
+	LIMIT_OPTION_DEFAULT,		/* No limit present */
+} LimitOption;
+
 #endif							/* NODES_H */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index cd6f1be6435..518abe42c10 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -159,6 +159,7 @@ typedef struct Query
 
 	Node	   *limitOffset;	/* # of result tuples to skip (int8 expr) */
 	Node	   *limitCount;		/* # of result tuples to return (int8 expr) */
+	LimitOption limitOption;	/* limit type */
 
 	List	   *rowMarks;		/* a list of RowMarkClause's */
 
@@ -1617,6 +1618,7 @@ typedef struct SelectStmt
 	List	   *sortClause;		/* sort clause (a list of SortBy's) */
 	Node	   *limitOffset;	/* # of result tuples to skip */
 	Node	   *limitCount;		/* # of result tuples to return */
+	LimitOption limitOption;	/* limit type */
 	List	   *lockingClause;	/* FOR UPDATE (list of LockingClause's) */
 	WithClause *withClause;		/* WITH clause */
 
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index a6d206b25a3..d76f88001b2 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -1824,6 +1824,7 @@ typedef struct LimitPath
 	Path	   *subpath;		/* path representing input source */
 	Node	   *limitOffset;	/* OFFSET parameter, or NULL if none */
 	Node	   *limitCount;		/* COUNT parameter, or NULL if none */
+	LimitOption limitOption;	/* FETCH FIRST with ties or exact number */
 } LimitPath;
 
 
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index be8ef54a1e4..55f363f70c5 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -982,6 +982,11 @@ typedef struct Limit
 	Plan		plan;
 	Node	   *limitOffset;	/* OFFSET parameter, or NULL if none */
 	Node	   *limitCount;		/* COUNT parameter, or NULL if none */
+	LimitOption limitOption;	/* limit type */
+	int			uniqNumCols;	/* number of columns to check for similarity  */
+	AttrNumber *uniqColIdx;		/* their indexes in the target list */
+	Oid		   *uniqOperators;	/* equality operators to compare with */
+	Oid		   *uniqCollations; /* collations for equality comparisons */
 } Limit;
 
 
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h
index bcd08af753e..715a24ad29a 100644
--- a/src/include/optimizer/pathnode.h
+++ b/src/include/optimizer/pathnode.h
@@ -268,6 +268,7 @@ extern ModifyTablePath *create_modifytable_path(PlannerInfo *root,
 extern LimitPath *create_limit_path(PlannerInfo *root, RelOptInfo *rel,
 									Path *subpath,
 									Node *limitOffset, Node *limitCount,
+									LimitOption limitOption,
 									int64 offset_est, int64 count_est);
 extern void adjust_limit_rows_costs(double *rows,
 									Cost *startup_cost, Cost *total_cost,
diff --git a/src/include/optimizer/planmain.h b/src/include/optimizer/planmain.h
index 47812010015..f3cefe67b8d 100644
--- a/src/include/optimizer/planmain.h
+++ b/src/include/optimizer/planmain.h
@@ -56,7 +56,10 @@ extern Agg *make_agg(List *tlist, List *qual,
 					 int numGroupCols, AttrNumber *grpColIdx, Oid *grpOperators, Oid *grpCollations,
 					 List *groupingSets, List *chain, double dNumGroups,
 					 Size transitionSpace, Plan *lefttree);
-extern Limit *make_limit(Plan *lefttree, Node *limitOffset, Node *limitCount);
+extern Limit *make_limit(Plan *lefttree, Node *limitOffset, Node *limitCount,
+						 LimitOption limitOption, int uniqNumCols,
+						 AttrNumber *uniqColIdx, Oid *uniqOperators,
+						 Oid *uniqCollations);
 
 /*
  * prototypes for plan/initsplan.c
diff --git a/src/include/parser/parse_clause.h b/src/include/parser/parse_clause.h
index d65ea3c3be2..75a4fcfa598 100644
--- a/src/include/parser/parse_clause.h
+++ b/src/include/parser/parse_clause.h
@@ -23,7 +23,8 @@ extern int	setTargetTable(ParseState *pstate, RangeVar *relation,
 extern Node *transformWhereClause(ParseState *pstate, Node *clause,
 								  ParseExprKind exprKind, const char *constructName);
 extern Node *transformLimitClause(ParseState *pstate, Node *clause,
-								  ParseExprKind exprKind, const char *constructName);
+								  ParseExprKind exprKind, const char *constructName,
+								  LimitOption limitOption);
 extern List *transformGroupClause(ParseState *pstate, List *grouplist,
 								  List **groupingSets,
 								  List **targetlist, List *sortClause,