F312 Add grammar support for MERGE

parser/sql/dialect/firebird/src/main/antlr4/imports/firebird/BaseRule.g4

@@ -173,6 +173,10 @@ baseSortName
     : identifier
     ;
 
+variableName
+    : identifier
+    ;
+
 constraintName
     : identifier
     ;

parser/sql/dialect/firebird/src/main/antlr4/imports/firebird/DMLStatement.g4

@@ -191,3 +191,44 @@ cteClause
     : identifier (LP_ columnNames RP_)? AS subquery
     ;
 
+merge
+    : MERGE intoClause usingClause
+    mergeWhen (mergeWhen)*
+    (RETURNING returnExprListClause (INTO variableListClause)?)?
+    ;
+
+intoClause
+    : INTO (tableName | viewName | subquery) (AS? alias)?
+    ;
+
+usingClause
+    : USING ((tableName | viewName) | subquery) (AS? alias)? ON predicate
+    ;
+
+mergeWhen
+    : mergeWhenMatched | mergeWhenNotMatched
+    ;
+
+mergeWhenMatched
+    : WHEN MATCHED (AND predicate)? THEN (UPDATE SET columnName EQ_ expr (COMMA_ (columnName EQ_ expr))* | DELETE )
+    ;
+
+mergeWhenNotMatched
+    : WHEN NOT MATCHED (AND predicate)? THEN INSERT columnNames? VALUES LP_ expr RP_
+    ;
+
+returnExpr
+    : expr (AS? alias)
+    ;
+
+returnExprListClause
+    : returnExpr (COMMA_ returnExpr)*
+    ;
+
+variableList
+    : LBT_ COLON_ RBT_ variableName
+    ;
+
+variableListClause
+    : variableList (COMMA_ variableList)*
+    ;

parser/sql/dialect/firebird/src/main/antlr4/imports/firebird/FirebirdKeyword.g4

@@ -855,6 +855,18 @@ STARTING
     : S T A R T I N G
     ;
 
+MERGE
+    : M E R G E
+    ;
+
+RETURNING
+    : R E T U R N I N G
+    ;
+
+MATCHED
+    : M A T C H E D
+    ;
+
 PASSWORD
     : P A S S W O R D
     ;

parser/sql/dialect/firebird/src/main/antlr4/org/apache/shardingsphere/sql/parser/autogen/FirebirdStatement.g4

@@ -49,6 +49,7 @@ execute
     | alterTrigger
     | executeBlock
     | createSequence
+    | merge
     | createUser
     | executeStmt
     ) SEMI_?

parser/sql/dialect/firebird/src/main/java/org/apache/shardingsphere/sql/parser/firebird/visitor/statement/type/FirebirdDMLStatementVisitor.java

@@ -52,6 +52,9 @@
 import org.apache.shardingsphere.sql.parser.autogen.FirebirdStatementParser.TableReferencesContext;
 import org.apache.shardingsphere.sql.parser.autogen.FirebirdStatementParser.UpdateContext;
 import org.apache.shardingsphere.sql.parser.autogen.FirebirdStatementParser.WhereClauseContext;
+import org.apache.shardingsphere.sql.parser.autogen.FirebirdStatementParser.MergeContext;
+import org.apache.shardingsphere.sql.parser.autogen.FirebirdStatementParser.IntoClauseContext;
+import org.apache.shardingsphere.sql.parser.autogen.FirebirdStatementParser.UsingClauseContext;
 import org.apache.shardingsphere.sql.parser.sql.common.enums.JoinType;
 import org.apache.shardingsphere.sql.parser.sql.common.segment.dml.assignment.AssignmentSegment;
 import org.apache.shardingsphere.sql.parser.sql.common.segment.dml.assignment.ColumnAssignmentSegment;
@@ -92,6 +95,7 @@
 import org.apache.shardingsphere.sql.parser.sql.dialect.statement.firebird.dml.FirebirdInsertStatement;
 import org.apache.shardingsphere.sql.parser.sql.dialect.statement.firebird.dml.FirebirdSelectStatement;
 import org.apache.shardingsphere.sql.parser.sql.dialect.statement.firebird.dml.FirebirdUpdateStatement;
+import org.apache.shardingsphere.sql.parser.sql.dialect.statement.firebird.dml.FirebirdMergeStatement;
 import org.apache.shardingsphere.sql.parser.firebird.visitor.statement.FirebirdStatementVisitor;
 
 import java.util.Collection;
@@ -479,4 +483,14 @@ public ASTNode visitGroupByClause(final GroupByClauseContext ctx) {
     public ASTNode visitSubquery(final SubqueryContext ctx) {
         return visit(ctx.combineClause());
     }
+
+    @Override
+    public ASTNode visitMerge(final MergeContext ctx) {
+        FirebirdMergeStatement result = new FirebirdMergeStatement();
+        result.setTarget((TableSegment) visit(ctx.intoClause()));
+        result.setSource((TableSegment) visit(ctx.usingClause()));
+        // add mergeWhenNotMatched and mergeWhenMatched part
+        // add RETURNING part
+        return result;
+    }
 }

parser/sql/statement/src/main/java/org/apache/shardingsphere/sql/parser/sql/dialect/statement/firebird/dml/FirebirdMergeStatement.java

@@ -0,0 +1,27 @@
+/*
+ * 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.
+ */
+
+package org.apache.shardingsphere.sql.parser.sql.dialect.statement.firebird.dml;
+
+import org.apache.shardingsphere.sql.parser.sql.common.statement.dml.MergeStatement;
+import org.apache.shardingsphere.sql.parser.sql.dialect.statement.firebird.FirebirdStatement;
+
+/**
+ * Firebird merge statement.
+ */
+public final class FirebirdMergeStatement extends MergeStatement implements FirebirdStatement {
+}