improved sql parser.

src/main/java/com/alibaba/druid/sql/dialect/postgresql/ast/PGWithClause.java

@@ -48,4 +48,15 @@ public class PGWithClause extends PGSQLObjectImpl {
         }
         visitor.endVisit(this);
     }
+
+    public PGWithClause clone() {
+        PGWithClause x = new PGWithClause();
+        x.recursive = recursive;
+        for (PGWithQuery w : withQuery) {
+            PGWithQuery w2 = w.clone();
+            w2.setParent(x);
+            x.withQuery.add(w2);
+        }
+        return x;
+    }
 }

src/main/java/com/alibaba/druid/sql/dialect/postgresql/ast/PGWithQuery.java

@@ -64,4 +64,22 @@ public class PGWithQuery extends PGSQLObjectImpl {
         }
         visitor.endVisit(this);
     }
+
+    public PGWithQuery clone() {
+        PGWithQuery x = new PGWithQuery();
+
+        if (name != null) {
+            x.setName(name.clone());
+        }
+        for (SQLExpr c : columns) {
+            SQLExpr c2 = c.clone();
+            c2.setParent(x);
+            x.columns.add(c);
+        }
+        if (query != null) {
+            x.setQuery(query.clone());
+        }
+
+        return x;
+    }
 }

src/main/java/com/alibaba/druid/sql/dialect/postgresql/ast/expr/PGIntervalExpr.java

@@ -65,4 +65,12 @@ public class PGIntervalExpr extends SQLExprImpl implements SQLLiteralExpr,PGExpr
     protected void accept0(SQLASTVisitor visitor) {
         this.accept0((PGASTVisitor) visitor);
     }
+
+    public PGIntervalExpr clone() {
+        PGIntervalExpr x = new PGIntervalExpr();
+        if (value != null) {
+            x.setValue(value.clone());
+        }
+        return x;
+    }
 }

src/main/java/com/alibaba/druid/sql/dialect/postgresql/ast/stmt/PGInsertStatement.java

@@ -31,6 +31,22 @@ public class PGInsertStatement extends SQLInsertStatement implements PGSQLStatem
     private SQLExpr            returning;
     private boolean			   defaultValues = false;
 
+    public void cloneTo(PGInsertStatement x) {
+        super.cloneTo(x);
+        if (with != null) {
+            x.setWith(with.clone());
+        }
+        for (ValuesClause v : valuesList) {
+            ValuesClause v2 = v.clone();
+            v2.setParent(x);
+            x.valuesList.add(v2);
+        }
+        if (returning != null) {
+            x.setReturning(returning.clone());
+        }
+        x.defaultValues = defaultValues;
+    }
+
     public SQLExpr getReturning() {
         return returning;
     }
@@ -96,4 +112,10 @@ public class PGInsertStatement extends SQLInsertStatement implements PGSQLStatem
 
         visitor.endVisit(this);
     }
+
+    public PGInsertStatement clone() {
+        PGInsertStatement x = new PGInsertStatement();
+        cloneTo(x);
+        return x;
+    }
 }