Read-only databases: some queries (such as distinct queries) tried to create…

Read-only databases: some queries (such as distinct queries) tried to create temporary tables, which failed for read only databases.

h2/src/docsrc/html/changelog.html

@@ -18,7 +18,9 @@ Change Log
 <h1>Change Log</h1>
 
 <h2>Next Version (unreleased)</h2>
-<ul><li>This database no longer uses finalize() except for temporary files.
+<ul><li>Read-only databases: some queries (such as distinct queries)
+    tried to create temporary tables, which failed for read only databases.
+</li><li>This database no longer uses finalize() except for temporary files.
     The system property "h2.runFinalize" is no longer supported.
     Unclosed connections are still detected, but the opening stack trace is now collected
     only if connections are not closed repeatedly (starting with the second unclosed connection).

h2/src/main/org/h2/result/LocalResult.java

@@ -253,7 +253,7 @@ public class LocalResult implements ResultInterface, ResultTarget {
                 distinctRows.put(array, values);
                 rowCount = distinctRows.size();
                 Database db = session.getDatabase();
-                if (rowCount > db.getSettings().maxMemoryRowsDistinct && db.isPersistent()) {
+                if (rowCount > db.getSettings().maxMemoryRowsDistinct && db.isPersistent() && !db.isReadOnly()) {
                     external = new ResultTempTable(session, sort);
                     rowCount = external.addRows(distinctRows.values());
                     distinctRows = null;
@@ -268,7 +268,10 @@ public class LocalResult implements ResultInterface, ResultTarget {
         if (rows.size() > maxMemoryRows && session.getDatabase().isPersistent()) {
             if (external == null) {
                 if (randomAccess) {
+                    Database db = session.getDatabase();
+                    if (!db.isReadOnly()) {
                         external = new ResultTempTable(session, sort);
+                    }
                 } else {
                     external = new ResultDiskBuffer(session, sort, values.length);
                 }
@@ -308,7 +311,10 @@ public class LocalResult implements ResultInterface, ResultTarget {
                         }
                         if (external == null) {
                             if (randomAccess) {
+                                Database db = session.getDatabase();
+                                if (!db.isReadOnly()) {
                                     external = new ResultTempTable(session, sort);
+                                }
                             } else {
                                 external = new ResultDiskBuffer(session, sort, list.length);
                             }

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

@@ -36,6 +36,7 @@ public class TestReadOnly extends TestBase {
         if (config.memory) {
             return;
         }
+        testReadOnlyTempTableResult();
         testReadOnlyConnect();
         testReadOnlyDbCreate();
         if (!config.googleAppEngine) {
@@ -45,6 +46,18 @@ public class TestReadOnly extends TestBase {
         deleteDb("readonly");
     }
 
+    private void testReadOnlyTempTableResult() throws SQLException {
+        deleteDb("readonly");
+        Connection conn = getConnection("readonly");
+        Statement stat = conn.createStatement();
+        stat.execute("CREATE TABLE TEST(ID INT) AS SELECT X FROM SYSTEM_RANGE(1, 20)");
+        conn.close();
+        conn = getConnection("readonly;ACCESS_MODE_DATA=r;MAX_MEMORY_ROWS_DISTINCT=10");
+        stat = conn.createStatement();
+        stat.execute("SELECT DISTINCT ID FROM TEST");
+        conn.close();
+    }
+
     private void testReadOnlyDbCreate() throws SQLException {
         deleteDb("readonly");
         Connection conn = getConnection("readonly");