improved sql parser.

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

@@ -22,6 +22,14 @@ public class PGBoxExpr extends PGExprImpl {
 
     private SQLExpr value;
 
+    public PGBoxExpr clone() {
+        PGBoxExpr x = new PGBoxExpr();
+        if (value != null) {
+            x.setValue(value.clone());
+        }
+        return x;
+    }
+
     public SQLExpr getValue() {
         return value;
     }

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

@@ -22,6 +22,14 @@ public class PGCidrExpr extends PGExprImpl {
 
     private SQLExpr value;
 
+    public PGCidrExpr clone() {
+        PGCidrExpr x = new PGCidrExpr();
+        if (value != null) {
+            x.setValue(value.clone());
+        }
+        return x;
+    }
+
     public SQLExpr getValue() {
         return value;
     }

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

@@ -22,6 +22,14 @@ public class PGCircleExpr extends PGExprImpl {
 
     private SQLExpr value;
 
+    public PGCircleExpr clone() {
+        PGCircleExpr x = new PGCircleExpr();
+        if (value != null) {
+            x.setValue(value.clone());
+        }
+        return x;
+    }
+
     public SQLExpr getValue() {
         return value;
     }

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

@@ -23,6 +23,15 @@ public class PGExtractExpr extends PGExprImpl {
     private PGDateField field;
     private SQLExpr     source;
 
+    public PGExtractExpr clone() {
+        PGExtractExpr x = new PGExtractExpr();
+        x.field = field;
+        if (source != null) {
+            x.setSource(source.clone());
+        }
+        return x;
+    }
+
     public PGDateField getField() {
         return field;
     }
@@ -36,6 +45,9 @@ public class PGExtractExpr extends PGExprImpl {
     }
 
     public void setSource(SQLExpr source) {
+        if (source != null) {
+            source.setParent(this);
+        }
         this.source = source;
     }
 

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

@@ -22,6 +22,14 @@ public class PGInetExpr extends PGExprImpl {
 
     private SQLExpr value;
 
+    public PGInetExpr clone() {
+        PGInetExpr x = new PGInetExpr();
+        if (value != null) {
+            x.setValue(value.clone());
+        }
+        return x;
+    }
+
     public SQLExpr getValue() {
         return value;
     }

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

@@ -22,6 +22,14 @@ public class PGLineSegmentsExpr extends PGExprImpl {
 
     private SQLExpr value;
 
+    public PGLineSegmentsExpr clone() {
+        PGLineSegmentsExpr x = new PGLineSegmentsExpr();
+        if (value != null) {
+            x.setValue(value.clone());
+        }
+        return x;
+    }
+
     public SQLExpr getValue() {
         return value;
     }

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

@@ -23,6 +23,14 @@ public class PGMacAddrExpr extends PGExprImpl {
 
     private SQLExpr value;
 
+    public PGMacAddrExpr clone() {
+        PGMacAddrExpr x = new PGMacAddrExpr();
+        if (value != null) {
+            x.setValue(value.clone());
+        }
+        return x;
+    }
+
     public SQLExpr getValue() {
         return value;
     }

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

@@ -22,6 +22,14 @@ public class PGPointExpr extends PGExprImpl {
 
     private SQLExpr value;
 
+    public PGPointExpr clone() {
+        PGPointExpr x = new PGPointExpr();
+        if (value != null) {
+            x.setValue(value.clone());
+        }
+        return x;
+    }
+
     public SQLExpr getValue() {
         return value;
     }

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

@@ -23,6 +23,14 @@ public class PGPolygonExpr extends PGExprImpl {
 
     private SQLExpr value;
 
+    public PGPolygonExpr clone() {
+        PGPolygonExpr x = new PGPolygonExpr();
+        if (value != null) {
+            x.setValue(value.clone());
+        }
+        return x;
+    }
+
     public SQLExpr getValue() {
         return value;
     }