From fbc537ef1d2b316d0b847da15663767808724814 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E9=AB=98=E9=93=81?= <shaojin.wensj@alibaba-inc.com>
Date: Tue, 26 Jan 2016 11:40:51 +0800
Subject: [PATCH] PagerUtils support count(distinct)

---
 .../java/com/alibaba/druid/sql/PagerUtils.java  | 17 ++++++++++++++---
 .../bvt/sql/PagerUtilsTest_Count_MySql_0.java   |  7 +++++++
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/src/main/java/com/alibaba/druid/sql/PagerUtils.java b/src/main/java/com/alibaba/druid/sql/PagerUtils.java
index becce579fd..8598ec1240 100644
--- a/src/main/java/com/alibaba/druid/sql/PagerUtils.java
+++ b/src/main/java/com/alibaba/druid/sql/PagerUtils.java
@@ -20,8 +20,10 @@ import java.util.List;
 import com.alibaba.druid.sql.ast.SQLExpr;
 import com.alibaba.druid.sql.ast.SQLOrderBy;
 import com.alibaba.druid.sql.ast.SQLOver;
+import com.alibaba.druid.sql.ast.SQLSetQuantifier;
 import com.alibaba.druid.sql.ast.SQLStatement;
 import com.alibaba.druid.sql.ast.expr.SQLAggregateExpr;
+import com.alibaba.druid.sql.ast.expr.SQLAggregateOption;
 import com.alibaba.druid.sql.ast.expr.SQLAllColumnExpr;
 import com.alibaba.druid.sql.ast.expr.SQLBinaryOpExpr;
 import com.alibaba.druid.sql.ast.expr.SQLBinaryOperator;
@@ -334,9 +336,18 @@ public class PagerUtils {
             if (queryBlock.getGroupBy() != null && queryBlock.getGroupBy().getItems().size() > 0) {
                 return createCountUseSubQuery(select, dbType);
             }
-
-            queryBlock.getSelectList().clear();
-            queryBlock.getSelectList().add(countItem);
+            
+            int option = queryBlock.getDistionOption();
+            if (option == SQLSetQuantifier.DISTINCT && queryBlock.getSelectList().size() == 1) {
+                SQLSelectItem firstItem = queryBlock.getSelectList().get(0);
+                SQLAggregateExpr exp = new SQLAggregateExpr("COUNT", SQLAggregateOption.DISTINCT);
+                exp.getArguments().add(firstItem.getExpr());
+                firstItem.setExpr(exp);
+                queryBlock.setDistionOption(0);
+            } else {
+                queryBlock.getSelectList().clear();
+                queryBlock.getSelectList().add(countItem);
+            }
             return SQLUtils.toSQLString(select, dbType);
         } else if (query instanceof SQLUnionQuery) {
             return createCountUseSubQuery(select, dbType);
diff --git a/src/test/java/com/alibaba/druid/bvt/sql/PagerUtilsTest_Count_MySql_0.java b/src/test/java/com/alibaba/druid/bvt/sql/PagerUtilsTest_Count_MySql_0.java
index 8a2c901796..754f3cb9e8 100644
--- a/src/test/java/com/alibaba/druid/bvt/sql/PagerUtilsTest_Count_MySql_0.java
+++ b/src/test/java/com/alibaba/druid/bvt/sql/PagerUtilsTest_Count_MySql_0.java
@@ -29,6 +29,13 @@ public class PagerUtilsTest_Count_MySql_0 extends TestCase {
         Assert.assertEquals("SELECT COUNT(*)\n" + //
                             "FROM t", result);
     }
+    
+    public void test_mysql_3() throws Exception {
+        String sql = "select distinct id from t order by id";
+        String result = PagerUtils.count(sql, JdbcConstants.MYSQL);
+        Assert.assertEquals("SELECT COUNT(DISTINCT id)\n" + //
+                            "FROM t", result);
+    }
 
     public void test_mysql_group_0() throws Exception {
         String sql = "select type, count(*) from t group by type";