Adding parser changes for OPTIONAL MATCH keyword

geaflow/geaflow-dsl/geaflow-dsl-parser/src/main/codegen/config.fmpp

@@ -72,7 +72,8 @@ data: {
         "DIFFERENT",
         "PARTITIONED",
         "YIELD",
-        "IF"
+        "IF",
+        "OPTIONAL"
     ]
 
     # let noReservedKeywords can be a identifier
@@ -435,6 +436,8 @@ data: {
                 "USING"
                 "YIELD"
                 "NEXT"
+                "OPTIONAL"
+
     ]
 
     # List of additional join types. Each is a method with no arguments.

geaflow/geaflow-dsl/geaflow-dsl-parser/src/main/codegen/includes/gqlQuery.ftl

@@ -3,18 +3,18 @@ SqlCall GQLMatchStatement() :
       SqlCall statement = null;
 }
 {
-      <MATCH> statement = SqlMatchPattern(statement)
+      statement = SqlMatchPattern(statement)
       (
         (
           statement = SqlLetStatement(statement) (<COMMA> statement = SqlLetStatement(statement))*
           [
-            [ <NEXT> ] <MATCH>
+            [ <NEXT> ]
             statement = SqlMatchPattern(statement)
           ]
         )
         |
         (
-           [ <NEXT> ] <MATCH>
+           [ <NEXT> ]
            statement = SqlMatchPattern(statement)
         )
       )*
@@ -366,8 +366,10 @@ SqlMatchPattern SqlMatchPattern(SqlNode preMatch) :
     SqlNode condition = null;
     SqlNodeList orderBy = null;
     SqlNode count = null;
+    boolean optional = false;
 }
 {
+    [ <OPTIONAL> { optional = true; } ] <MATCH>
     pathPattern = SqlUnionPathPattern()  { pathList.add(pathPattern); }
     ( <COMMA> pathPattern = SqlUnionPathPattern()  { pathList.add(pathPattern); } )*
 
@@ -387,7 +389,7 @@ SqlMatchPattern SqlMatchPattern(SqlNode preMatch) :
     ]
     {
         graphPattern = new SqlNodeList(pathList, s.addAll(pathList).pos());
-        return new SqlMatchPattern(s.end(this), preMatch, graphPattern, condition, orderBy, count);
+        return new SqlMatchPattern(s.end(this), preMatch, graphPattern, condition, orderBy, count, optional);
     }
 }
 

geaflow/geaflow-dsl/geaflow-dsl-parser/src/main/java/org/apache/geaflow/dsl/operator/SqlMatchPatternOperator.java

@@ -30,16 +30,16 @@ public class SqlMatchPatternOperator extends SqlOperator {
 
     private SqlMatchPatternOperator() {
         super("MatchPattern", SqlKind.OTHER, 2, true,
-            ReturnTypes.SCOPE, null, null);
+                ReturnTypes.SCOPE, null, null);
     }
 
     @Override
     public SqlCall createCall(
-        SqlLiteral functionQualifier,
-        SqlParserPos pos,
-        SqlNode... operands) {
+            SqlLiteral functionQualifier,
+            SqlParserPos pos,
+            SqlNode... operands) {
         return new SqlMatchPattern(pos, operands[0], (SqlNodeList) operands[1], operands[2],
-            (SqlNodeList) operands[3], operands[4]);
+                (SqlNodeList) operands[3], operands[4], false);
     }
 
     @Override
@@ -49,10 +49,10 @@ public SqlSyntax getSyntax() {
 
     @Override
     public void unparse(
-        SqlWriter writer,
-        SqlCall call,
-        int leftPrec,
-        int rightPrec) {
+            SqlWriter writer,
+            SqlCall call,
+            int leftPrec,
+            int rightPrec) {
         call.unparse(writer, leftPrec, rightPrec);
     }
 }

geaflow/geaflow-dsl/geaflow-dsl-parser/src/main/java/org/apache/geaflow/dsl/sqlnode/SqlMatchPattern.java

@@ -39,14 +39,17 @@ public class SqlMatchPattern extends SqlCall {
 
     private SqlNode limit;
 
+    private boolean optional;
+
     public SqlMatchPattern(SqlParserPos pos, SqlNode from, SqlNodeList pathPatterns,
-                           SqlNode where, SqlNodeList orderBy, SqlNode limit) {
+            SqlNode where, SqlNodeList orderBy, SqlNode limit, boolean optional) {
         super(pos);
         this.from = from;
         this.pathPatterns = pathPatterns;
         this.where = where;
         this.orderBy = orderBy;
         this.limit = limit;
+        this.optional = optional;
     }
 
     @Override
@@ -57,7 +60,7 @@ public SqlOperator getOperator() {
     @Override
     public List<SqlNode> getOperandList() {
         return ImmutableNullableList.of(getFrom(), getPathPatterns(), getWhere(),
-            getOrderBy(), getLimit());
+                getOrderBy(), getLimit());
     }
 
     @Override
@@ -82,7 +85,6 @@ public SqlNodeList getOrderBy() {
         return orderBy;
     }
 
-
     public SqlNode getLimit() {
         return limit;
     }
@@ -170,4 +172,8 @@ public void setWhere(SqlNode where) {
     public boolean isSinglePattern() {
         return pathPatterns.size() == 1 && pathPatterns.get(0) instanceof SqlPathPattern;
     }
+
+    public boolean isOptional() {
+        return optional;
+    }
 }

geaflow/geaflow-dsl/geaflow-dsl-parser/src/test/java/org/apache/geaflow/dsl/MatchReturnSyntaxTest.java

@@ -80,4 +80,11 @@ public void testGQLMatchOrder() throws Exception {
         String unParseStmts = parseStmtsAndUnParse(parseStmtsAndUnParse(unParseSql));
         Assert.assertEquals(unParseStmts, unParseSql);
     }
+
+    @Test
+    public void testGQLOptionalMatch() throws Exception {
+        String unParseSql = parseSqlAndUnParse("GQLOptionalMatch.sql");
+        String unParseStmts = parseStmtsAndUnParse(parseStmtsAndUnParse(unParseSql));
+        Assert.assertEquals(unParseStmts, unParseSql);
+    }
 }

geaflow/geaflow-dsl/geaflow-dsl-parser/src/test/resources/GQLOptionalMatch.sql

@@ -0,0 +1,23 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+OPTIONAL MATCH (a:Person) RETURN a.name;
+MATCH (a:Person) OPTIONAL MATCH (a)-[:Knows]->(b:Person) RETURN a.name, b.name;
+OPTIONAL MATCH (a:Person) WHERE a.age > 20 RETURN a.name;
+MATCH (a:Person) OPTIONAL MATCH (a)-[:Knows]->(b:Person) OPTIONAL MATCH (b)-[:Knows]->(c:Person) RETURN a.name, b.name, c.name;