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

1 files changed, 55 insertions, 3 deletions

diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index 6c76c41ebea..3c302db0575 100644
--- a/src/backend/nodes/nodeFuncs.c
+++ b/src/backend/nodes/nodeFuncs.c
@@ -2146,6 +2146,16 @@ expression_tree_walker(Node *node,
 					return true;
 			}
 			break;
+		case T_MergeAction:
+			{
+				MergeAction *action = (MergeAction *) node;
+
+				if (walker(action->targetList, context))
+					return true;
+				if (walker(action->qual, context))
+					return true;
+			}
+			break;
 		case T_JoinExpr:
 			{
 				JoinExpr   *join = (JoinExpr *) node;
@@ -2255,6 +2265,10 @@ query_tree_walker(Query *query,
 		return true;
 	if (walker((Node *) query->onConflict, context))
 		return true;
+	if (walker((Node *) query->mergeSourceTargetList, context))
+		return true;
+	if (walker((Node *) query->mergeActionList, context))
+		return true;
 	if (walker((Node *) query->returningList, context))
 		return true;
 	if (walker((Node *) query->jointree, context))
@@ -2932,6 +2946,18 @@ expression_tree_mutator(Node *node,
 				return (Node *) newnode;
 			}
 			break;
+		case T_MergeAction:
+			{
+				MergeAction *action = (MergeAction *) node;
+				MergeAction *newnode;
+
+				FLATCOPY(newnode, action, MergeAction);
+				MUTATE(newnode->qual, action->qual, Node *);
+				MUTATE(newnode->targetList, action->targetList, List *);
+
+				return (Node *) newnode;
+			}
+			break;
 		case T_JoinExpr:
 			{
 				JoinExpr   *join = (JoinExpr *) node;
@@ -3083,6 +3109,8 @@ query_tree_mutator(Query *query,
 	MUTATE(query->targetList, query->targetList, List *);
 	MUTATE(query->withCheckOptions, query->withCheckOptions, List *);
 	MUTATE(query->onConflict, query->onConflict, OnConflictExpr *);
+	MUTATE(query->mergeSourceTargetList, query->mergeSourceTargetList, List *);
+	MUTATE(query->mergeActionList, query->mergeActionList, List *);
 	MUTATE(query->returningList, query->returningList, List *);
 	MUTATE(query->jointree, query->jointree, FromExpr *);
 	MUTATE(query->setOperations, query->setOperations, Node *);
@@ -3224,9 +3252,9 @@ query_or_expression_tree_mutator(Node *node,
  * boundaries: we descend to everything that's possibly interesting.
  *
  * Currently, the node type coverage here extends only to DML statements
- * (SELECT/INSERT/UPDATE/DELETE) and nodes that can appear in them, because
- * this is used mainly during analysis of CTEs, and only DML statements can
- * appear in CTEs.
+ * (SELECT/INSERT/UPDATE/DELETE/MERGE) and nodes that can appear in them,
+ * because this is used mainly during analysis of CTEs, and only DML
+ * statements can appear in CTEs.
  */
 bool
 raw_expression_tree_walker(Node *node,
@@ -3406,6 +3434,30 @@ raw_expression_tree_walker(Node *node,
 					return true;
 			}
 			break;
+		case T_MergeStmt:
+			{
+				MergeStmt  *stmt = (MergeStmt *) node;
+
+				if (walker(stmt->relation, context))
+					return true;
+				if (walker(stmt->source_relation, context))
+					return true;
+				if (walker(stmt->join_condition, context))
+					return true;
+				if (walker(stmt->mergeActionList, context))
+					return true;
+			}
+			break;
+		case T_MergeAction:
+			{
+				MergeAction *action = (MergeAction *) node;
+
+				if (walker(action->targetList, context))
+					return true;
+				if (walker(action->qual, context))
+					return true;
+			}
+			break;
 		case T_SelectStmt:
 			{
 				SelectStmt *stmt = (SelectStmt *) node;