Sub-query cache is getting dropped in Session.prepareLocal now + more tests.

h2/src/main/org/h2/engine/Session.java

@@ -483,6 +483,8 @@ public class Session extends SessionWithState {
         }
         Parser parser = new Parser(this);
         command = parser.prepareCommand(sql);
+        // we can't reuse view indexes from sub-queries, so just drop the cache
+        subQueryIndexCache = null;
         if (queryCache != null) {
             if (command.isCacheable()) {
                 queryCache.put(sql, command);
@@ -1319,8 +1321,8 @@ public class Session extends SessionWithState {
 
     public Map<Object, ViewIndex> getViewIndexCache(boolean subQuery) {
         if (subQuery) {
-            // for sub-queries we don't need to use LRU because it should not grow too large
-            // for a single query and by the end of the statement we will drop the whole cache
+            // for sub-queries we don't need to use LRU because the cache should not
+            // grow too large for a single query (we drop the whole cache in the end of prepareLocal)
             if (subQueryIndexCache == null) {
                 subQueryIndexCache = New.hashMap();
             }
@@ -1510,7 +1512,6 @@ public class Session extends SessionWithState {
      */
     public void endStatement() {
         startStatement = -1;
-        subQueryIndexCache = null;
         closeTemporaryResults();
     }
 

h2/src/test/org/h2/test/db/TestView.java

@@ -10,8 +10,9 @@ import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.Statement;
-
 import org.h2.api.ErrorCode;
+import org.h2.engine.Session;
+import org.h2.jdbc.JdbcConnection;
 import org.h2.test.TestBase;
 
 /**
@@ -33,7 +34,7 @@ public class TestView extends TestBase {
     @Override
     public void test() throws SQLException {
         deleteDb("view");
-
+        testSubQueryViewIndexCache();
         testInnerSelectWithRownum();
         testInnerSelectWithRange();
         testEmptyColumn();
@@ -51,6 +52,53 @@ public class TestView extends TestBase {
         deleteDb("view");
     }
 
+    public void testSubQueryViewIndexCache() throws SQLException {
+        if (config.networked) {
+            return;
+        }
+        Connection conn = getConnection("view");
+        Statement stat = conn.createStatement();
+        stat.execute("drop table test if exists");
+        stat.execute("create table test(id int primary key, name varchar(25) unique, age int unique)");
+
+        // check that initial cache size is empty
+        Session s = (Session) ((JdbcConnection) conn).getSession();
+        s.clearViewIndexCache();
+        assertTrue(s.getViewIndexCache(true).isEmpty());
+        assertTrue(s.getViewIndexCache(false).isEmpty());
+
+        // create view command should not affect caches
+        stat.execute("create view v as select * from test");
+        assertTrue(s.getViewIndexCache(true).isEmpty());
+        assertTrue(s.getViewIndexCache(false).isEmpty());
+
+        // check view index cache
+        stat.executeQuery("select * from v where id > 0").next();
+        int size1 = s.getViewIndexCache(false).size();
+        assertTrue(size1 > 0);
+        assertTrue(s.getViewIndexCache(true).isEmpty());
+        stat.executeQuery("select * from v where name = 'xyz'").next();
+        int size2 = s.getViewIndexCache(false).size();
+        assertTrue(size2 > size1);
+        assertTrue(s.getViewIndexCache(true).isEmpty());
+
+        // check we did not add anything to view cache if we run a sub-query
+        stat.executeQuery("select * from (select * from test) where age = 17").next();
+        int size3 = s.getViewIndexCache(false).size();
+        assertEquals(size2, size3);
+        assertTrue(s.getViewIndexCache(true).isEmpty());
+
+        // check clear works
+        s.clearViewIndexCache();
+        assertTrue(s.getViewIndexCache(false).isEmpty());
+        assertTrue(s.getViewIndexCache(true).isEmpty());
+
+        // drop everything
+        stat.execute("drop view v");
+        stat.execute("drop table test");
+        conn.close();
+    }
+
     private void testInnerSelectWithRownum() throws SQLException {
         Connection conn = getConnection("view");
         Statement stat = conn.createStatement();