From 16dc2703c5413534d4989e08253e8f4fcb0e2aab Mon Sep 17 00:00:00 2001
From: Tom Lane
Date: Wed, 5 Apr 2023 16:59:00 -0400
Subject: Support "Right Anti Join" plan shapes.

Merge and hash joins can support antijoin with the non-nullable input
on the right, using very simple combinations of their existing logic
for right join and anti join.  This gives the planner more freedom
about how to order the join.  It's particularly useful for hash join,
since we may now have the option to hash the smaller table instead
of the larger.

Richard Guo, reviewed by Ronan Dunklau and myself

Discussion: https://postgr.es/m/CAMbWs48xh9hMzXzSy3VaPzGAz+fkxXXTUbCLohX1_L8THFRm2Q@mail.gmail.com
---
 src/include/nodes/execnodes.h | 3 ++-
 src/include/nodes/nodes.h     | 4 +++-
 src/include/nodes/pathnodes.h | 5 +++--
 3 files changed, 8 insertions(+), 4 deletions(-)

(limited to 'src/include/nodes')

diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index d97f5a8e7dc..b0def732ca6 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -2073,7 +2073,8 @@ typedef struct MergeJoinState
  *								OuterTupleSlot is empty!)
  *		hj_OuterTupleSlot		tuple slot for outer tuples
  *		hj_HashTupleSlot		tuple slot for inner (hashed) tuples
- *		hj_NullOuterTupleSlot	prepared null tuple for right/full outer joins
+ *		hj_NullOuterTupleSlot	prepared null tuple for right/right-anti/full
+ *								outer joins
  *		hj_NullInnerTupleSlot	prepared null tuple for left/full outer joins
  *		hj_FirstOuterTupleSlot	first tuple retrieved from outer plan
  *		hj_JoinState			current state of ExecHashJoin state machine
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index bdfef0f461d..f8e8fe699ab 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -317,6 +317,7 @@ typedef enum JoinType
 	 */
 	JOIN_SEMI,					/* 1 copy of each LHS row that has match(es) */
 	JOIN_ANTI,					/* 1 copy of each LHS row that has no match */
+	JOIN_RIGHT_ANTI,			/* 1 copy of each RHS row that has no match */
 
 	/*
 	 * These codes are used internally in the planner, but are not supported
@@ -349,7 +350,8 @@ typedef enum JoinType
 	  ((1 << JOIN_LEFT) | \
 	   (1 << JOIN_FULL) | \
 	   (1 << JOIN_RIGHT) | \
-	   (1 << JOIN_ANTI))) != 0)
+	   (1 << JOIN_ANTI) | \
+	   (1 << JOIN_RIGHT_ANTI))) != 0)
 
 /*
  * AggStrategy -
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index d61a62da196..cf28416da84 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -2766,8 +2766,9 @@ typedef struct PlaceHolderVar
  * min_lefthand and min_righthand for higher joins.)
  *
  * jointype is never JOIN_RIGHT; a RIGHT JOIN is handled by switching
- * the inputs to make it a LEFT JOIN.  So the allowed values of jointype
- * in a join_info_list member are only LEFT, FULL, SEMI, or ANTI.
+ * the inputs to make it a LEFT JOIN.  It's never JOIN_RIGHT_ANTI either.
+ * So the allowed values of jointype in a join_info_list member are only
+ * LEFT, FULL, SEMI, or ANTI.
  *
  * ojrelid is the RT index of the join RTE representing this outer join,
  * if there is one.  It is zero when jointype is INNER or SEMI, and can be
-- 
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