Linked tables that point to the same database now share the connection.

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

@@ -49,6 +49,7 @@ import org.h2.table.IndexColumn;
 import org.h2.table.MetaTable;
 import org.h2.table.Table;
 import org.h2.table.TableData;
+import org.h2.table.TableLinkConnection;
 import org.h2.table.TableView;
 import org.h2.tools.DeleteDbFiles;
 import org.h2.tools.Server;
@@ -160,6 +161,7 @@ public class Database implements DataHandler {
     private boolean autoServerMode;
     private Object reserveMemory;
     private Server server;
+    private HashMap linkConnections;
 
     public Database(String name, ConnectionInfo ci, String cipher) throws SQLException {
         this.compareMode = new CompareMode(null, null, 0);
@@ -2053,5 +2055,21 @@ public class Database implements DataHandler {
     public void freeReserveMemory() {
         reserveMemory = null;
     }
+    
+    /**
+     * Open a new connection or get an existing connection to another database.
+     * 
+     * @param driver the database driver or null
+     * @param url the database URL
+     * @param user the user name
+     * @param password the password
+     * @return the connection
+     */
+    public TableLinkConnection getLinkConnection(String driver, String url, String user, String password) throws SQLException {
+        if (linkConnections == null) {
+            linkConnections = new HashMap();
+        }
+        return TableLinkConnection.open(linkConnections, driver, url, user, password);
+    }
 
 }

h2/src/main/org/h2/index/LinkedIndex.java

@@ -67,19 +67,21 @@ public class LinkedIndex extends BaseIndex {
         }
         buff.append(')');
         String sql = buff.toString();
-        try {
-            PreparedStatement prep = link.getPreparedStatement(sql);
-            for (int i = 0, j = 0; i < row.getColumnCount(); i++) {
-                Value v = row.getValue(i);
-                if (v != null && v != ValueNull.INSTANCE) {
-                    v.set(prep, j + 1);
-                    j++;
+        synchronized (link.getConnection()) {
+            try {
+                PreparedStatement prep = link.getPreparedStatement(sql);
+                for (int i = 0, j = 0; i < row.getColumnCount(); i++) {
+                    Value v = row.getValue(i);
+                    if (v != null && v != ValueNull.INSTANCE) {
+                        v.set(prep, j + 1);
+                        j++;
+                    }
                 }
+                prep.executeUpdate();
+                rowCount++;
+            } catch (SQLException e) {
+                throw wrapException(sql, e);
             }
-            prep.executeUpdate();
-            rowCount++;
-        } catch (SQLException e) {
-            throw wrapException(sql, e);
         }
     }
 
@@ -114,27 +116,29 @@ public class LinkedIndex extends BaseIndex {
         }
         buff.insert(0, "SELECT * FROM " + targetTableName + " T");
         String sql = buff.toString();
-        try {
-            PreparedStatement prep = link.getPreparedStatement(sql);
-            int j = 0;
-            for (int i = 0; first != null && i < first.getColumnCount(); i++) {
-                Value v = first.getValue(i);
-                if (v != null) {
-                    v.set(prep, j + 1);
-                    j++;
+        synchronized (link.getConnection()) {
+            try {
+                PreparedStatement prep = link.getPreparedStatement(sql);
+                int j = 0;
+                for (int i = 0; first != null && i < first.getColumnCount(); i++) {
+                    Value v = first.getValue(i);
+                    if (v != null) {
+                        v.set(prep, j + 1);
+                        j++;
+                    }
                 }
-            }
-            for (int i = 0; last != null && i < last.getColumnCount(); i++) {
-                Value v = last.getValue(i);
-                if (v != null) {
-                    v.set(prep, j + 1);
-                    j++;
+                for (int i = 0; last != null && i < last.getColumnCount(); i++) {
+                    Value v = last.getValue(i);
+                    if (v != null) {
+                        v.set(prep, j + 1);
+                        j++;
+                    }
                 }
+                ResultSet rs = prep.executeQuery();
+                return new LinkedCursor(table, rs, session);
+            } catch (SQLException e) {
+                throw wrapException(sql, e);
             }
-            ResultSet rs = prep.executeQuery();
-            return new LinkedCursor(table, rs, session);
-        } catch (SQLException e) {
-            throw wrapException(sql, e);
         }
     }
     
@@ -202,19 +206,21 @@ public class LinkedIndex extends BaseIndex {
             }
         }
         String sql = buff.toString();
-        try {
-            PreparedStatement prep = link.getPreparedStatement(sql);
-            for (int i = 0, j = 0; i < row.getColumnCount(); i++) {
-                Value v = row.getValue(i);
-                if (!isNull(v)) {
-                    v.set(prep, j + 1);
-                    j++;
+        synchronized (link.getConnection()) {
+            try {
+                PreparedStatement prep = link.getPreparedStatement(sql);
+                for (int i = 0, j = 0; i < row.getColumnCount(); i++) {
+                    Value v = row.getValue(i);
+                    if (!isNull(v)) {
+                        v.set(prep, j + 1);
+                        j++;
+                    }
                 }
+                int count = prep.executeUpdate();
+                rowCount -= count;
+            } catch (SQLException e) {
+                throw wrapException(sql, e);
             }
-            int count = prep.executeUpdate();
-            rowCount -= count;
-        } catch (SQLException e) {
-            throw wrapException(sql, e);
         }
     }
 
@@ -251,25 +257,27 @@ public class LinkedIndex extends BaseIndex {
             }
         }
         String sql = buff.toString();
-        try {
-            int j = 1;
-            PreparedStatement prep = link.getPreparedStatement(sql);
-            for (int i = 0; i < newRow.getColumnCount(); i++) {
-                newRow.getValue(i).set(prep, j);
-                j++;
-            }
-            for (int i = 0; i < oldRow.getColumnCount(); i++) {
-                Value v = oldRow.getValue(i);
-                if (!isNull(v)) {
-                    v.set(prep, j);
+        synchronized (link.getConnection()) {
+            try {
+                int j = 1;
+                PreparedStatement prep = link.getPreparedStatement(sql);
+                for (int i = 0; i < newRow.getColumnCount(); i++) {
+                    newRow.getValue(i).set(prep, j);
                     j++;
                 }
+                for (int i = 0; i < oldRow.getColumnCount(); i++) {
+                    Value v = oldRow.getValue(i);
+                    if (!isNull(v)) {
+                        v.set(prep, j);
+                        j++;
+                    }
+                }
+                int count = prep.executeUpdate();
+                // this has no effect but at least it allows to debug the update count
+                rowCount = rowCount + count - count;
+            } catch (SQLException e) {
+                throw wrapException(sql, e);
             }
-            int count = prep.executeUpdate();
-            // this has no effect but at least it allows to debug the update count
-            rowCount = rowCount + count - count;
-        } catch (SQLException e) {
-            throw wrapException(sql, e);
         }
     }
 

h2/src/main/org/h2/table/TableLink.java

@@ -6,7 +6,6 @@
  */
 package org.h2.table;
 
-import java.sql.Connection;
 import java.sql.DatabaseMetaData;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
@@ -40,7 +39,7 @@ import org.h2.value.DataType;
 public class TableLink extends Table {
 
     private String driver, url, user, password, originalSchema, originalTable, qualifiedTableName;
-    private Connection conn;
+    private TableLinkConnection conn;
     private HashMap prepared = new HashMap();
     private final ObjectArray indexes = new ObjectArray();
     private final boolean emitUpdates;
@@ -77,8 +76,20 @@ public class TableLink extends Table {
     }
 
     private void connect() throws SQLException {
-        conn = JdbcUtils.getConnection(driver, url, user, password);
-        DatabaseMetaData meta = conn.getMetaData();
+        conn = database.getLinkConnection(driver, url, user, password);
+        synchronized (conn) {
+            try {
+                readMetaData();
+            } catch (SQLException e) {
+                conn.close();
+                conn = null;
+                throw e;
+            }
+        }
+    }
+    
+    private void readMetaData() throws SQLException {
+        DatabaseMetaData meta = conn.getConnection().getMetaData();
         storesLowerCase = meta.storesLowerCaseIdentifiers();
         storesMixedCase = meta.storesMixedCaseIdentifiers();
         supportsMixedCaseIdentifiers = meta.supportsMixedCaseIdentifiers();        
@@ -129,7 +140,7 @@ public class TableLink extends Table {
         // check if the table is accessible
         Statement stat = null;
         try {
-            stat = conn.createStatement();
+            stat = conn.getConnection().createStatement();
             rs = stat.executeQuery("SELECT * FROM " + qualifiedTableName + " T WHERE 1=0");
             if (columnList.size() == 0) {
                 // alternative solution
@@ -359,7 +370,7 @@ public class TableLink extends Table {
         }
         PreparedStatement prep = (PreparedStatement) prepared.get(sql);
         if (prep == null) {
-            prep = conn.prepareStatement(sql);
+            prep = conn.getConnection().prepareStatement(sql);
             prepared.put(sql, prep);
         }
         return prep;
@@ -399,7 +410,6 @@ public class TableLink extends Table {
         database.removeMeta(session, getId());
         driver = null;
         url = user = password = originalTable = null;
-        conn = null;
         prepared = null;
         invalidate();
     }
@@ -457,4 +467,8 @@ public class TableLink extends Table {
         this.readOnly = readOnly;
     }
 
+    public TableLinkConnection getConnection() {
+        return conn;
+    }
+
 }

h2/src/main/org/h2/util/ObjectUtils.java

@@ -195,4 +195,14 @@ public class ObjectUtils {
         }
     }
 
+    /**
+     * Calculate the hash code of the given object. The object may be null.
+     * 
+     * @param the object
+     * @return the hash code, or 0 if the object is null
+     */
+    public static int hashCode(Object o) {
+        return o == null ? 0 : o.hashCode();
+    }
+
 }

h2/src/test/org/h2/test/TestAll.java

@@ -276,8 +276,6 @@ java org.h2.test.TestAll timer
 
 test on linux
 
-main methods for the tests and make that work
-
 TestMVCC:
 Concurrent update in table test: another transaction has updated or 
 deleted the same row when exactly does it occur in other databases 

h2/src/test/org/h2/test/TestBase.java

@@ -41,7 +41,7 @@ public abstract class TestBase {
      */
     protected TestAll config;
     
-    private long start;
+    protected long start;
 
     /**
      * Get the test directory for this test.

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

@@ -73,6 +73,7 @@ public class TestLinkedTable extends TestBase {
         sa.execute("CREATE SCHEMA P");
         sa.execute("CREATE TABLE P.TEST(X INT)");
         sa.execute("INSERT INTO TEST VALUES(1)");
+        sa.execute("INSERT INTO P.TEST VALUES(2)");
         try {
             sb.execute("CREATE LINKED TABLE T(NULL, 'jdbc:h2:mem:one', 'sa', 'sa', 'TEST')");
             fail();
@@ -81,6 +82,8 @@ public class TestLinkedTable extends TestBase {
         }
         sb.execute("CREATE LINKED TABLE T(NULL, 'jdbc:h2:mem:one', 'sa', 'sa', 'PUBLIC', 'TEST')");
         sb.execute("CREATE LINKED TABLE T2(NULL, 'jdbc:h2:mem:one', 'sa', 'sa', 'P', 'TEST')");
+        assertSingleValue(sb, "SELECT * FROM T", 1);
+        assertSingleValue(sb, "SELECT * FROM T2", 2);
         sa.execute("DROP ALL OBJECTS");
         sb.execute("DROP ALL OBJECTS");
         ca.close();

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

@@ -21,7 +21,7 @@ import org.h2.util.JdbcUtils;
  */
 public class TestListener extends TestBase implements DatabaseEventListener {
 
-    private long last, start;
+    private long last;
     private int lastState = -1;
     private String url;