Use UserVmDao for listVirtualMachines API to increase performance

framework/db/src/main/java/com/cloud/utils/db/GenericDaoBase.java

@@ -1264,6 +1264,11 @@ protected StringBuilder createPartialSelectSql(SearchCriteria<?> sc, final boole
 
     @DB()
     protected void addJoins(StringBuilder str, Collection<JoinBuilder<SearchCriteria<?>>> joins) {
+        addJoins(str, joins, new HashMap<>());
+    }
+
+    @DB()
+    protected void addJoins(StringBuilder str, Collection<JoinBuilder<SearchCriteria<?>>> joins, Map<String, Integer> joinedTableNames) {
         boolean hasWhereClause = true;
         int fromIndex = str.lastIndexOf("WHERE");
         if (fromIndex == -1) {
@@ -1274,18 +1279,27 @@ protected void addJoins(StringBuilder str, Collection<JoinBuilder<SearchCriteria
         }
 
         for (JoinBuilder<SearchCriteria<?>> join : joins) {
+            String joinTableName = join.getSecondAttribute().table;
+            String joinTableAlias = findNextJoinTableName(joinTableName, joinedTableNames);
             StringBuilder onClause = new StringBuilder();
             onClause.append(" ")
             .append(join.getType().getName())
             .append(" ")
-            .append(join.getSecondAttribute().table)
-            .append(" ON ")
+            .append(joinTableName);
+            if (!joinTableAlias.equals(joinTableName)) {
+                onClause.append(" ").append(joinTableAlias);
+            }
+            onClause.append(" ON ")
             .append(join.getFirstAttribute().table)
             .append(".")
             .append(join.getFirstAttribute().columnName)
-            .append("=")
-            .append(join.getSecondAttribute().table)
-            .append(".")
+            .append("=");
+            if(!joinTableAlias.equals(joinTableName)) {
+                onClause.append(joinTableAlias);
+            } else {
+                onClause.append(joinTableName);
+            }
+            onClause.append(".")
             .append(join.getSecondAttribute().columnName)
             .append(" ");
             str.insert(fromIndex, onClause);
@@ -1306,11 +1320,22 @@ protected void addJoins(StringBuilder str, Collection<JoinBuilder<SearchCriteria
 
         for (JoinBuilder<SearchCriteria<?>> join : joins) {
             if (join.getT().getJoins() != null) {
-                addJoins(str, join.getT().getJoins());
+                addJoins(str, join.getT().getJoins(), joinedTableNames);
             }
         }
     }
 
+    protected static String findNextJoinTableName(String tableName, Map<String, Integer> usedTableNames) {
+        if (usedTableNames.containsKey(tableName)) {
+            Integer tableCounter = usedTableNames.get(tableName);
+            usedTableNames.put(tableName, ++tableCounter);
+            tableName = tableName + tableCounter;
+        } else {
+            usedTableNames.put(tableName, 0);
+        }
+        return tableName;
+    }
+
     private void removeAndClause(StringBuilder sql) {
         sql.delete(sql.length() - 4, sql.length());
     }

framework/db/src/test/java/com/cloud/utils/db/GenericDaoBaseTest.java

@@ -18,6 +18,10 @@
 
 import java.sql.ResultSet;
 import java.sql.SQLException;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
 
 import org.junit.Assert;
 import org.junit.Before;
@@ -36,6 +40,7 @@ public class GenericDaoBaseTest {
     @Mock
     SQLException mockedSQLException;
 
+    private static final DbTestDao dbTestDao = new DbTestDao();
     private static final String INTEGRITY_CONSTRAINT_VIOLATION = "23000";
     private static final int DUPLICATE_ENTRY_ERRO_CODE = 1062;
 
@@ -214,4 +219,51 @@ public void checkCountOfRecordsAgainstTheResultSetSizeTestCountSmallerThanResult
 
         Assert.assertEquals(resultSetSize, result);
     }
+
+    @Test
+    public void addJoinsTest() {
+        StringBuilder joinString = new StringBuilder();
+        Collection<JoinBuilder<SearchCriteria<?>>> joins = new ArrayList<>();
+
+        Attribute attr1 = new Attribute("table1", "column1");
+        Attribute attr2 = new Attribute("table2", "column2");
+        Attribute attr3 = new Attribute("table3", "column1");
+        Attribute attr4 = new Attribute("table4", "column2");
+
+        joins.add(new JoinBuilder<>(dbTestDao.createSearchCriteria(), attr1, attr2, JoinBuilder.JoinType.INNER));
+        joins.add(new JoinBuilder<>(dbTestDao.createSearchCriteria(), attr3, attr4, JoinBuilder.JoinType.INNER));
+        dbTestDao.addJoins(joinString, joins);
+
+        Assert.assertEquals(" INNER JOIN table2 ON table1.column1=table2.column2  INNER JOIN table4 ON table3.column1=table4.column2 ", joinString.toString());
+    }
+
+    @Test
+    public void multiJoinSameTableTest() {
+        StringBuilder joinString = new StringBuilder();
+        Collection<JoinBuilder<SearchCriteria<?>>> joins = new ArrayList<>();
+
+        Attribute tAc1 = new Attribute("tableA", "column1");
+        Attribute tAc2 = new Attribute("tableA", "column2");
+        Attribute tAc3 = new Attribute("tableA", "column3");
+        Attribute tBc2 = new Attribute("tableB", "column2");
+        Attribute tCc3 = new Attribute("tableC", "column3");
+        Attribute tDc4 = new Attribute("tableD", "column4");
+
+        joins.add(new JoinBuilder<>(dbTestDao.createSearchCriteria(), tBc2, tAc1, JoinBuilder.JoinType.INNER));
+        joins.add(new JoinBuilder<>(dbTestDao.createSearchCriteria(), tCc3, tAc2, JoinBuilder.JoinType.INNER));
+        joins.add(new JoinBuilder<>(dbTestDao.createSearchCriteria(), tDc4, tAc3, JoinBuilder.JoinType.INNER));
+        dbTestDao.addJoins(joinString, joins);
+
+        Assert.assertEquals(" INNER JOIN tableA ON tableB.column2=tableA.column1  INNER JOIN tableA tableA1 ON tableC.column3=tableA1.column2  INNER JOIN tableA tableA2 ON tableD.column4=tableA2.column3 ", joinString.toString());
+    }
+
+    @Test
+    public void findNextTableNameTest() {
+        Map<String, Integer> usedTables = new HashMap<>();
+
+        Assert.assertEquals("tableA", GenericDaoBase.findNextJoinTableName("tableA", usedTables));
+        Assert.assertEquals("tableA1", GenericDaoBase.findNextJoinTableName("tableA", usedTables));
+        Assert.assertEquals("tableA2", GenericDaoBase.findNextJoinTableName("tableA", usedTables));
+        Assert.assertEquals("tableA3", GenericDaoBase.findNextJoinTableName("tableA", usedTables));
+    }
 }