improve sql wall, support rand

src/main/java/com/alibaba/druid/sql/dialect/db2/visitor/DB2EvalVisitor.java

@@ -135,6 +135,11 @@ public class DB2EvalVisitor extends DB2ASTVisitorAdapter implements SQLEvalVisit
     public void registerFunction(String funcName, Function function) {
         functions.put(funcName, function);
     }
+    
+    @Override
+    public void unregisterFunction(String funcName) {
+        functions.remove(funcName);
+    }
 
     public boolean visit(SQLIdentifierExpr x) {
         return SQLEvalVisitorUtils.visit(this, x);

src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlEvalVisitorImpl.java

@@ -162,4 +162,9 @@ public class MySqlEvalVisitorImpl extends MySqlASTVisitorAdapter implements SQLE
     public boolean visit(SQLIdentifierExpr x) {
         return SQLEvalVisitorUtils.visit(this, x);
     }
+
+    @Override
+    public void unregisterFunction(String funcName) {
+        functions.remove(funcName);
+    }
 }

src/main/java/com/alibaba/druid/sql/dialect/oracle/visitor/OracleEvalVisitor.java

@@ -135,6 +135,11 @@ public class OracleEvalVisitor extends OracleASTVisitorAdapter implements SQLEva
     public void registerFunction(String funcName, Function function) {
         functions.put(funcName, function);
     }
+    
+    @Override
+    public void unregisterFunction(String funcName) {
+        functions.remove(funcName);
+    }
 
     public boolean visit(SQLIdentifierExpr x) {
         return SQLEvalVisitorUtils.visit(this, x);

src/main/java/com/alibaba/druid/sql/dialect/postgresql/visitor/PGEvalVisitor.java

@@ -135,6 +135,11 @@ public class PGEvalVisitor extends PGASTVisitorAdapter implements SQLEvalVisitor
     public void registerFunction(String funcName, Function function) {
         functions.put(funcName, function);
     }
+    
+    @Override
+    public void unregisterFunction(String funcName) {
+        functions.remove(funcName);
+    }
 
     public boolean visit(SQLIdentifierExpr x) {
         return SQLEvalVisitorUtils.visit(this, x);

src/main/java/com/alibaba/druid/sql/dialect/sqlserver/visitor/SQLServerEvalVisitor.java

@@ -136,6 +136,11 @@ public class SQLServerEvalVisitor extends SQLServerASTVisitorAdapter implements
         functions.put(funcName, function);
     }
     
+    @Override
+    public void unregisterFunction(String funcName) {
+        functions.remove(funcName);
+    }
+    
     public boolean visit(SQLIdentifierExpr x) {
         return SQLEvalVisitorUtils.visit(this, x);
     }

src/main/java/com/alibaba/druid/sql/visitor/SQLEvalVisitor.java

@@ -30,6 +30,8 @@ public interface SQLEvalVisitor extends SQLASTVisitor {
     Function getFunction(String funcName);
 
     void registerFunction(String funcName, Function function);
+    
+    void unregisterFunction(String funcName);
 
     List<Object> getParameters();
 

src/main/java/com/alibaba/druid/sql/visitor/SQLEvalVisitorImpl.java

@@ -138,4 +138,9 @@ public class SQLEvalVisitorImpl extends SQLASTVisitorAdapter implements SQLEvalV
     public boolean visit(SQLIdentifierExpr x) {
         return SQLEvalVisitorUtils.visit(this, x);
     }
+
+    @Override
+    public void unregisterFunction(String funcName) {
+        functions.remove(funcName);
+    }
 }

src/main/java/com/alibaba/druid/sql/visitor/SQLEvalVisitorUtils.java

@@ -228,7 +228,11 @@ public class SQLEvalVisitorUtils {
     public static boolean visit(SQLEvalVisitor visitor, SQLMethodInvokeExpr x) {
         String methodName = x.getMethodName().toLowerCase();
 
-        Function function = functions.get(methodName);
+        Function function = visitor.getFunction(methodName);
+
+        if (function == null) {
+            function = functions.get(methodName);
+        }
 
         if (function != null) {
             Object result = function.eval(visitor, x);

src/main/java/com/alibaba/druid/sql/visitor/functions/Nil.java

@@ -0,0 +1,15 @@
+package com.alibaba.druid.sql.visitor.functions;
+
+import com.alibaba.druid.sql.ast.expr.SQLMethodInvokeExpr;
+import com.alibaba.druid.sql.visitor.SQLEvalVisitor;
+
+public class Nil implements Function {
+
+    public final static Nil instance = new Nil();
+
+    @Override
+    public Object eval(SQLEvalVisitor visitor, SQLMethodInvokeExpr x) {
+        return null;
+    }
+
+}

src/main/java/com/alibaba/druid/wall/spi/WallVisitorUtils.java

@@ -100,7 +100,9 @@ import com.alibaba.druid.sql.dialect.oracle.ast.stmt.OracleMergeStatement;
 import com.alibaba.druid.sql.dialect.oracle.ast.stmt.OracleMultiInsertStatement;
 import com.alibaba.druid.sql.dialect.sqlserver.ast.stmt.SQLServerExecStatement;
 import com.alibaba.druid.sql.visitor.ExportParameterVisitor;
+import com.alibaba.druid.sql.visitor.SQLEvalVisitor;
 import com.alibaba.druid.sql.visitor.SQLEvalVisitorUtils;
+import com.alibaba.druid.sql.visitor.functions.Nil;
 import com.alibaba.druid.support.logging.Log;
 import com.alibaba.druid.support.logging.LogFactory;
 import com.alibaba.druid.util.JdbcUtils;
@@ -739,7 +741,7 @@ public class WallVisitorUtils {
             dbType = wallContext.getDbType();
         }
 
-        return SQLEvalVisitorUtils.eval(dbType, x, Collections.emptyList(), false);
+        return eval(dbType, x, Collections.emptyList());
     }
 
     public static SQLExpr getFirst(SQLExpr x) {
@@ -1042,7 +1044,7 @@ public class WallVisitorUtils {
             || x instanceof SQLInListExpr //
             || x instanceof SQLUnaryExpr //
         ) {
-            return SQLEvalVisitorUtils.eval(dbType, x, Collections.emptyList(), false);
+            return eval(dbType, x, Collections.emptyList());
         }
 
         if (visitor != null && (!visitor.getConfig().isCaseConditionAllow()) && x instanceof SQLCaseExpr) {
@@ -1065,11 +1067,21 @@ public class WallVisitorUtils {
                 }
             }
 
-            return SQLEvalVisitorUtils.eval(dbType, x, Collections.emptyList(), false);
+            return eval(dbType, x, Collections.emptyList());
         }
 
         return null;
     }
+    
+    public static Object eval(String dbType, SQLObject sqlObject, List<Object> parameters) {
+        SQLEvalVisitor visitor = SQLEvalVisitorUtils.createEvalVisitor(dbType);
+        visitor.setParameters(parameters);
+        visitor.registerFunction("rand", Nil.instance);
+        sqlObject.accept(visitor);
+
+        Object value = SQLEvalVisitorUtils.getValue(sqlObject);
+        return value;
+    }
 
     public static boolean isSimpleCountTableSource(WallVisitor visitor, SQLTableSource tableSource) {
         if (!(tableSource instanceof SQLSubqueryTableSource)) {

src/test/java/com/alibaba/druid/bvt/filter/wall/MySqlWallTest144.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright 1999-2011 Alibaba Group Holding Ltd.
+ *
+ * Licensed 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 com.alibaba.druid.bvt.filter.wall;
+
+import junit.framework.TestCase;
+
+import org.junit.Assert;
+
+import com.alibaba.druid.wall.WallProvider;
+import com.alibaba.druid.wall.spi.MySqlWallProvider;
+
+public class MySqlWallTest144 extends TestCase {
+
+    public void test_false() throws Exception {
+        WallProvider provider = new MySqlWallProvider();
+
+        String sql = "select min(id) from wx_interact where activityid=1008 group by true_name,mobile having rand()<1";
+        Assert.assertTrue(provider.checkValid(sql));
+    }
+}