Merge pull request #1903 from GodzillaHua/master

mysql limit ? 或者 limit ?,?不进行替换，防止参数数量不匹配

src/main/java/com/alibaba/druid/sql/PagerUtils.java

@@ -381,6 +381,8 @@ public class PagerUtils {
                 if (rowCount <= count && offset <= 0) {
                     return false;
                 }
+            } else if (check && limit.getRowCount() instanceof SQLVariantRefExpr) {
+                return false;
             }
 
             limit.setRowCount(new SQLIntegerExpr(count));

src/test/java/com/alibaba/druid/bvt/sql/PagerUtilsTest_Limit_mysql_question_placeholder.java

@@ -0,0 +1,56 @@
+package com.alibaba.druid.bvt.sql;
+
+import com.alibaba.druid.sql.PagerUtils;
+import com.alibaba.druid.sql.SQLUtils;
+import com.alibaba.druid.sql.ast.SQLStatement;
+import com.alibaba.druid.sql.ast.statement.SQLSelect;
+import com.alibaba.druid.sql.ast.statement.SQLSelectStatement;
+import com.alibaba.druid.sql.parser.ParserException;
+import com.alibaba.druid.util.JdbcConstants;
+import junit.framework.TestCase;
+import org.junit.Assert;
+
+import java.util.List;
+
+public class PagerUtilsTest_Limit_mysql_question_placeholder extends TestCase {
+
+    public void  testQuestionLimitPlaceholder1(){
+        String sql = "select * from test_table limit ?";
+        testQuestionLimitPlaceholderInternal(sql);
+    }
+
+    public void  testQuestionLimitPlaceholder2(){
+        String sql = "select * from test_table limit ?, ?";
+        testQuestionLimitPlaceholderInternal(sql);
+    }
+
+    private void testQuestionLimitPlaceholderInternal(String sql){
+        List<SQLStatement> statements;
+        try{
+            statements = SQLUtils.parseStatements(sql, JdbcConstants.MYSQL);
+        }catch(ParserException e){
+            Assert.fail(e.getMessage());
+            return;
+        }
+        if (statements == null || statements.size() == 0){
+            Assert.fail("no sql found!");
+            return;
+        }
+        if (statements.size() != 1) {
+            Assert.fail("sql not support count : " + sql);
+            return;
+        }
+        SQLSelectStatement statement = (SQLSelectStatement)statements.get(0);
+        if (!(statement instanceof SQLSelectStatement)) {
+            Assert.fail("sql not support count : " + sql);
+            return;
+        }
+        SQLSelect select = statement.getSelect();
+        PagerUtils.limit(select, JdbcConstants.MYSQL, 0, 200, true);
+        SQLUtils.FormatOption options = new SQLUtils.FormatOption();
+        options.setPrettyFormat(false);
+        options.setUppCase(false);
+        assertEquals(sql, SQLUtils.toSQLString(select, JdbcConstants.MYSQL, options));
+    }
+
+}