WITH support in MERGE

Author: Peter Geoghegan
Recursive support removed, no tests
Docs added by me

5 files changed, 24 insertions, 5 deletions

diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 770ed3b1a88..c3efca3c452 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -3055,6 +3055,7 @@ _copyMergeStmt(const MergeStmt *from)
 	COPY_NODE_FIELD(source_relation);
 	COPY_NODE_FIELD(join_condition);
 	COPY_NODE_FIELD(mergeActionList);
+	COPY_NODE_FIELD(withClause);
 
 	return newnode;
 }
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 5a0151eece5..45ceba28309 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -1051,6 +1051,7 @@ _equalMergeStmt(const MergeStmt *a, const MergeStmt *b)
 	COMPARE_NODE_FIELD(source_relation);
 	COMPARE_NODE_FIELD(join_condition);
 	COMPARE_NODE_FIELD(mergeActionList);
+	COMPARE_NODE_FIELD(withClause);
 
 	return true;
 }
diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index 3c302db0575..4157e7eb9a3 100644
--- a/src/backend/nodes/nodeFuncs.c
+++ b/src/backend/nodes/nodeFuncs.c
@@ -3446,6 +3446,8 @@ raw_expression_tree_walker(Node *node,
 					return true;
 				if (walker(stmt->mergeActionList, context))
 					return true;
+				if (walker(stmt->withClause, context))
+					return true;
 			}
 			break;
 		case T_MergeAction:
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 583ee321e1d..b879358de16 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -11105,17 +11105,18 @@ set_target_list:
  *****************************************************************************/
 
 MergeStmt:
-			MERGE INTO relation_expr_opt_alias
+			opt_with_clause MERGE INTO relation_expr_opt_alias
 			USING table_ref
 			ON a_expr
 			merge_when_list
 				{
 					MergeStmt *m = makeNode(MergeStmt);
 
-					m->relation = $3;
-					m->source_relation = $5;
-					m->join_condition = $7;
-					m->mergeActionList = $8;
+					m->withClause = $1;
+					m->relation = $4;
+					m->source_relation = $6;
+					m->join_condition = $8;
+					m->mergeActionList = $9;
 
 					$$ = (Node *)m;
 				}
diff --git a/src/backend/parser/parse_merge.c b/src/backend/parser/parse_merge.c
index d6d6876961c..eb4c615ce1c 100644
--- a/src/backend/parser/parse_merge.c
+++ b/src/backend/parser/parse_merge.c
@@ -24,6 +24,7 @@
 #include "parser/parsetree.h"
 #include "parser/parser.h"
 #include "parser/parse_clause.h"
+#include "parser/parse_cte.h"
 #include "parser/parse_merge.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
@@ -202,6 +203,19 @@ transformMergeStmt(ParseState *pstate, MergeStmt *stmt)
 	Assert(pstate->p_ctenamespace == NIL);
 
 	qry->commandType = CMD_MERGE;
+	qry->hasRecursive = false;
+
+	/* process the WITH clause independently of all else */
+	if (stmt->withClause)
+	{
+		if (stmt->withClause->recursive)
+			ereport(ERROR,
+					(errcode(ERRCODE_SYNTAX_ERROR),
+					 errmsg("WITH RECURSIVE is not supported for MERGE statement")));
+
+		qry->cteList = transformWithClause(pstate, stmt->withClause);
+		qry->hasModifyingCTE = pstate->p_hasModifyingCTE;
+	}
 
 	/*
 	 * Check WHEN clauses for permissions and sanity