Parse WHEN MATCHED THEN and WHEN NOT MATCHED THEN in any order

h2/src/main/org/h2/command/Parser.java

@@ -1168,11 +1168,33 @@ public class Parser {
         command.setOnCondition(condition);
         read(")");
 
-        if (readIfAll("WHEN", "MATCHED", "THEN")) {
+        boolean matched = parseWhenMatched(command);
+        if (parseWhenNotMatched(command) && !matched) {
+            parseWhenMatched(command);
+        }
+
+        setSQL(command, "MERGE", start);
+
+        // build and prepare the targetMatchQuery ready to test each rows
+        // existence in the target table (using source row to match)
+        StringBuilder targetMatchQuerySQL = new StringBuilder("SELECT _ROWID_ FROM ");
+        appendTableWithSchemaAndAlias(targetMatchQuerySQL, command.getTargetTable(),
+                command.getTargetTableFilter().getTableAlias());
+        targetMatchQuerySQL
+                .append(" WHERE ").append(command.getOnCondition().getSQL());
+        command.setTargetMatchQuery(
+                (Select) parse(targetMatchQuerySQL.toString()));
+
+        return command;
+    }
+
+    private boolean parseWhenMatched(MergeUsing command) {
+        if (!readIfAll("WHEN", "MATCHED", "THEN")) {
+            return false;
+        }
         int startMatched = lastParseIndex;
         if (readIf("UPDATE")) {
             Update updateCommand = new Update(session);
-                //currentPrepared = updateCommand;
             TableFilter filter = command.getTargetTableFilter();
             updateCommand.setTableFilter(filter);
             parseUpdateSetClause(updateCommand, filter, startMatched);
@@ -1186,29 +1208,20 @@ public class Parser {
             parseDeleteGivenTable(deleteCommand, null, startMatched);
             command.setDeleteCommand(deleteCommand);
         }
+        return true;
+    }
+
+    private boolean parseWhenNotMatched(MergeUsing command) {
+        if (!readIfAll("WHEN", "NOT", "MATCHED", "THEN")) {
+            return false;
         }
-        if (readIfAll("WHEN", "NOT", "MATCHED", "THEN")) {
         if (readIf("INSERT")) {
             Insert insertCommand = new Insert(session);
             insertCommand.setTable(command.getTargetTable());
             parseInsertGivenTable(insertCommand, command.getTargetTable());
             command.setInsertCommand(insertCommand);
         }
-        }
-
-        setSQL(command, "MERGE", start);
-
-        // build and prepare the targetMatchQuery ready to test each rows
-        // existence in the target table (using source row to match)
-        StringBuilder targetMatchQuerySQL = new StringBuilder("SELECT _ROWID_ FROM ");
-        appendTableWithSchemaAndAlias(targetMatchQuerySQL, command.getTargetTable(),
-                command.getTargetTableFilter().getTableAlias());
-        targetMatchQuerySQL
-                .append(" WHERE ").append(command.getOnCondition().getSQL());
-        command.setTargetMatchQuery(
-                (Select) parse(targetMatchQuerySQL.toString()));
-
-        return command;
+        return true;
     }
 
     private static void appendTableWithSchemaAndAlias(StringBuilder buff, Table table, String alias) {