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

@@ -19,6 +19,7 @@ import org.h2.jdbc.JdbcConnection;
 import org.h2.message.Message;
 import org.h2.message.Trace;
 import org.h2.message.TraceSystem;
+import org.h2.result.Row;
 import org.h2.schema.Schema;
 import org.h2.store.DataHandler;
 import org.h2.store.InDoubtTransaction;
@@ -268,8 +269,12 @@ public class Session implements SessionInterface {
         }
         locks.add(table);
     }
+    
+    public void log(Table table, short type, Row row) throws SQLException {
+        log(new UndoLogRecord(table, type, row));
+    }
 
-    public void log(UndoLogRecord log) throws SQLException {
+    private void log(UndoLogRecord log) throws SQLException {
         // called _after_ the row was inserted successfully into the table,
         // otherwise rollback will try to rollback a not-inserted row
         if(Constants.CHECK) {

h2/src/main/org/h2/expression/Function.java

@@ -94,7 +94,7 @@ public class Function extends Expression implements FunctionCall {
             COALESCE = 204, NULLIF = 205, CASE = 206, NEXTVAL = 207, CURRVAL = 208,
             ARRAY_GET = 209, CSVREAD = 210, CSVWRITE = 211, MEMORY_FREE = 212,
             MEMORY_USED = 213, LOCK_MODE = 214, SCHEMA = 215, SESSION_ID = 216, ARRAY_LENGTH = 217,
-            LINK_SCHEMA = 218, TABLE = 219;
+            LINK_SCHEMA = 218, TABLE = 219, LEAST = 220, GREATEST = 221;
 
     private static final int VAR_ARGS = -1;
 
@@ -286,6 +286,8 @@ public class Function extends Expression implements FunctionCall {
         addFunction("ARRAY_LENGTH", ARRAY_LENGTH, 1, Value.INT);
         addFunction("LINK_SCHEMA", LINK_SCHEMA, 6, Value.RESULT_SET);
         addFunctionWithNull("TABLE", TABLE, VAR_ARGS, Value.RESULT_SET);
+        addFunctionWithNull("LEAST", LEAST, VAR_ARGS, Value.NULL);
+        addFunctionWithNull("GREATEST", GREATEST, VAR_ARGS, Value.NULL);
     }
 
     private static void addFunction(String name, int type, int parameterCount,
@@ -394,6 +396,27 @@ public class Function extends Expression implements FunctionCall {
             }
             return v0;
         }
+        case GREATEST:
+        case LEAST: {
+            Value result = ValueNull.INSTANCE;
+            for (int i = 0; i < args.length; i++) {
+                Value v = i==0 ? v0 : args[i].getValue(session);
+                if (!(v == ValueNull.INSTANCE)) {
+                    v = v.convertTo(dataType);
+                    if(result == ValueNull.INSTANCE) {
+                        result = v;
+                    } else {
+                        int comp = database.compareTypeSave(result, v);
+                        if(info.type == GREATEST && comp < 0 ) {
+                            result = v;
+                        } else if(info.type == LEAST && comp > 0 ) {
+                            result = v;
+                        }
+                    }
+                }
+            }
+            return result;
+        }
         case CASE: {
             // TODO function CASE: document & implement functionality
             int i = 0;
@@ -1220,6 +1243,8 @@ public class Function extends Expression implements FunctionCall {
             case COALESCE:
             case CSVREAD:
             case TABLE:
+            case LEAST:
+            case GREATEST:
                 min = 1;
                 break;
             case NOW:
@@ -1303,7 +1328,9 @@ public class Function extends Expression implements FunctionCall {
         switch (info.type) {
         case IFNULL:
         case NULLIF:
-        case COALESCE: {
+        case COALESCE:
+        case LEAST: 
+        case GREATEST: {
             dataType = Value.STRING;
             scale = 0;
             precision = 0;

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

@@ -78,39 +78,6 @@ public class LinkedIndex extends Index {
         }
     }
 
-    public void remove(Session session, Row row) throws SQLException {
-        StringBuffer buff = new StringBuffer("DELETE FROM ");
-        buff.append(originalTable);
-        buff.append(" WHERE ");
-        for(int i=0; i<row.getColumnCount(); i++) {
-            if(i>0) {
-                buff.append("AND ");
-            }
-            buff.append(table.getColumn(i).getSQL());
-            Value v = row.getValue(i);
-            if(isNull(v)) {
-                buff.append(" IS NULL ");
-            } else {
-                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(!isNull(v)) {
-                    v.set(prep, j+1);
-                    j++;
-                }
-            }
-            int count = prep.executeUpdate();
-            rowCount -= count;
-        } catch(SQLException e) {
-            throw Message.getSQLException(Message.ERROR_ACCESSING_LINKED_TABLE_1, new String[]{sql}, e);
-        }
-    }
-
     public Cursor find(Session session, SearchRow first, SearchRow last) throws SQLException {
         StringBuffer buff = new StringBuffer();
         for(int i=0; first != null && i<first.getColumnCount(); i++) {
@@ -196,6 +163,82 @@ public class LinkedIndex extends Index {
     public Value findFirstOrLast(Session session, boolean first) throws SQLException {
         // TODO optimization: could get the first or last value (in any case; maybe not optimized)
         throw Message.getUnsupportedException();
-    }    
+    }
+    
+    public void remove(Session session, Row row) throws SQLException {
+        StringBuffer buff = new StringBuffer("DELETE FROM ");
+        buff.append(originalTable);
+        buff.append(" WHERE ");
+        for(int i=0; i<row.getColumnCount(); i++) {
+            if(i>0) {
+                buff.append("AND ");
+            }
+            buff.append(table.getColumn(i).getSQL());
+            Value v = row.getValue(i);
+            if(isNull(v)) {
+                buff.append(" IS NULL ");
+            } else {
+                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(!isNull(v)) {
+                    v.set(prep, j+1);
+                    j++;
+                }
+            }
+            int count = prep.executeUpdate();
+            rowCount -= count;
+        } catch(SQLException e) {
+            throw Message.getSQLException(Message.ERROR_ACCESSING_LINKED_TABLE_1, new String[]{sql}, e);
+        }
+    }
+    
+    public void update(Session session, Row oldRow, Row newRow) throws SQLException {
+        StringBuffer buff = new StringBuffer("UPDATE ");
+        buff.append(originalTable).append(" SET ");
+        for (int i = 0; i < newRow.getColumnCount(); i++) {
+            if (i > 0) {
+                buff.append(", ");
+            }
+            buff.append(table.getColumn(i).getSQL()).append("=?");
+        }
+        buff.append(" WHERE ");
+        for(int i=0; i<oldRow.getColumnCount(); i++) {
+            if(i>0) {
+                buff.append("AND ");
+            }
+            buff.append(table.getColumn(i).getSQL());
+            Value v = oldRow.getValue(i);
+            if(isNull(v)) {
+                buff.append(" IS NULL ");
+            } else {
+                buff.append("=? ");
+            }
+        }
+        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);
+                    j++;
+                }
+            }
+            prep.executeUpdate();
+        } catch(SQLException e) {
+            throw Message.getSQLException(Message.ERROR_ACCESSING_LINKED_TABLE_1, new String[]{sql}, e);
+        }
+    }
 
 }

h2/src/main/org/h2/res/help.csv

@@ -362,9 +362,14 @@ CREATE INDEX IDXNAME ON TEST(NAME)
 CREATE LINKED TABLE [IF NOT EXISTS]
 name(driverString, urlString,
 userString, passwordString, originalTableString)
+[EMIT UPDATES]
 ","
 Creates a table link to an external table.
 The driver name may be empty if the driver is already loaded.
+Usually, for update statements, the old rows are deleted first 
+and then the new rows inserted. It is possible to emit update
+statements (however this is not possible on rollback), however
+in this case multi-row unique key updates may not always work.
 The current user owner must have admin rights.
 ","
 CREATE LINKED TABLE LINK('org.h2.Driver', 'jdbc:h2:test', 'sa', '', 'TEST')
@@ -2460,6 +2465,14 @@ Returns NULL otherwise.
 DATABASE_PATH()
 "
 
+"Functions (System)","GREATEST","
+GREATEST(aValue, bValue [,...]): value
+","
+Returns the largest value that is not NULL, or NULL if all values are NULL.
+","
+GREATEST(A, B, C)
+"
+
 "Functions (System)","IDENTITY","
 IDENTITY(): int
 ","
@@ -2476,6 +2489,14 @@ Returns the value of 'a' if it is not null, otherwise 'b'.
 IFNULL(A, B)
 "
 
+"Functions (System)","LEAST","
+LEAST(aValue, bValue [,...]): value
+","
+Returns the smallest value that is not NULL, or NULL if all values are NULL.
+","
+LEAST(A, B, C)
+"
+
 "Functions (System)","LOCK_MODE","
 LOCK_MODE(): int
 ","

h2/src/main/org/h2/server/web/AppServer.java

@@ -9,7 +9,6 @@ import java.io.FileOutputStream;
 import java.io.IOException;
 
 import java.sql.Connection;
-import java.sql.DriverManager;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.Properties;
@@ -211,8 +210,6 @@ public class AppServer {
         user = user.trim();
         password = password.trim();
         org.h2.Driver.load();
-        JdbcUtils.getConnection(driver, url, user, password);
-        Class.forName(driver);
 //            try {
 //                Driver dr = (Driver) urlClassLoader.loadClass(driver).newInstance();
 //                Properties p = new Properties();
@@ -222,7 +219,7 @@ public class AppServer {
 //            } catch(ClassNotFoundException e2) {
 //                throw e2;
 //            }
-        return DriverManager.getConnection(url, user, password);
+        return JdbcUtils.getConnection(driver, url, user, password);
     }
 
 }

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

@@ -7,6 +7,7 @@ package org.h2.table;
 import java.sql.SQLException;
 import java.util.HashMap;
 
+import org.h2.command.Prepared;
 import org.h2.constraint.Constraint;
 import org.h2.engine.Constants;
 import org.h2.engine.DbObject;
@@ -24,6 +25,7 @@ import org.h2.schema.Schema;
 import org.h2.schema.SchemaObject;
 import org.h2.schema.Sequence;
 import org.h2.schema.TriggerObject;
+import org.h2.store.UndoLogRecord;
 import org.h2.util.ObjectArray;
 import org.h2.value.Value;
 import org.h2.value.ValueNull;
@@ -125,6 +127,23 @@ public abstract class Table extends SchemaObject {
     public abstract ObjectArray getIndexes();
     public abstract boolean isLockedExclusively();
     public abstract long getMaxDataModificationId();
+    
+    public void updateRows(Prepared prepared, Session session, ObjectArray oldRows, ObjectArray newRows) throws SQLException {
+        // remove the old rows
+        for (int i = 0; i < oldRows.size(); i++) {
+            prepared.checkCancelled();
+            Row o = (Row) oldRows.get(i);
+            removeRow(session, o);
+            session.log(this, UndoLogRecord.DELETE, o);
+        }
+        // add the new rows
+        for (int i=0; i < newRows.size(); i++) {
+            prepared.checkCancelled();
+            Row n = (Row) newRows.get(i);
+            addRow(session, n);
+            session.log(this, UndoLogRecord.INSERT, n);
+        }
+    }
 
     public void removeChildrenAndResources(Session session) throws SQLException {        
         while(views != null && views.size() > 0) {

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

@@ -13,6 +13,7 @@ import java.sql.SQLException;
 import java.sql.Statement;
 import java.util.HashMap;
 
+import org.h2.command.Prepared;
 import org.h2.engine.Session;
 import org.h2.index.Index;
 import org.h2.index.IndexType;
@@ -20,6 +21,7 @@ import org.h2.index.LinkedIndex;
 import org.h2.message.Message;
 import org.h2.result.Row;
 import org.h2.schema.Schema;
+import org.h2.store.UndoLogRecord;
 import org.h2.util.JdbcUtils;
 import org.h2.util.ObjectArray;
 import org.h2.util.StringUtils;
@@ -35,15 +37,18 @@ public class TableLink extends Table {
     private Connection conn;
     private HashMap prepared = new HashMap();
     private ObjectArray indexes = new ObjectArray();
+    private boolean emitUpdates;
+    private LinkedIndex linkedIndex;
 
     public TableLink(Schema schema, int id, String name, String driver, String url, 
-            String user, String password, String originalTable) throws SQLException {
+            String user, String password, String originalTable, boolean emitUpdates) throws SQLException {
         super(schema, id, name, false);
         this.driver = driver;
         this.url = url;
         this.user = user;
         this.password = password;
         this.originalTable = originalTable;
+        this.emitUpdates = emitUpdates;
         conn = JdbcUtils.getConnection(driver, url, user, password);
         DatabaseMetaData meta = conn.getMetaData();
         boolean storesLowerCase = meta.storesLowerCaseIdentifiers();
@@ -94,8 +99,8 @@ public class TableLink extends Table {
         Column[] cols = new Column[columnList.size()];
         columnList.toArray(cols);
         setColumns(cols);
-        Index index = new LinkedIndex(this, id, cols, IndexType.createNonUnique(false));
-        indexes.add(index);
+        linkedIndex = new LinkedIndex(this, id, cols, IndexType.createNonUnique(false));
+        indexes.add(linkedIndex);
         rs = meta.getPrimaryKeys(null, null, originalTable);
         String pkName = "";
         ObjectArray list;
@@ -179,6 +184,9 @@ public class TableLink extends Table {
         buff.append(", ");
         buff.append(StringUtils.quoteStringSQL(originalTable));
         buff.append(")");
+        if(emitUpdates) {
+            buff.append(" EMIT UPDATES");
+        }
         return buff.toString();
     }
 
@@ -195,7 +203,7 @@ public class TableLink extends Table {
     }    
 
     public Index getScanIndex(Session session) {
-        return (Index) indexes.get(0);
+        return linkedIndex;
     }
 
     public void removeRow(Session session, Row row) throws SQLException {
@@ -294,4 +302,24 @@ public class TableLink extends Table {
         return null;
     }    
     
+    public void updateRows(Prepared prepared, Session session, ObjectArray oldRows, ObjectArray newRows) throws SQLException {
+        boolean deleteInsert;
+        if(emitUpdates) {
+            for (int i = 0; i < oldRows.size(); i++) {
+                session.checkCancelled();
+                Row oldRow = (Row) oldRows.get(i);
+                Row newRow = (Row) newRows.get(i);
+                linkedIndex.update(session, oldRow, newRow);
+                session.log(this, UndoLogRecord.DELETE, oldRow);
+                session.log(this, UndoLogRecord.INSERT, newRow);
+            }
+            deleteInsert = false;
+        } else {
+            deleteInsert = true;
+        }
+        if(deleteInsert) {
+            super.updateRows(prepared, session, oldRows, newRows);
+        }
+    }
+    
 }

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

@@ -13,9 +13,49 @@ public class TestLinkedTable extends TestBase {
 
     public void test() throws Exception {
         testLinkSchema();
+        testLinkEmitUpdates();
         testLinkTable();
     }
     
+    private void testLinkEmitUpdates() throws Exception {
+        deleteDb("linked1");
+        deleteDb("linked2");
+        Class.forName("org.h2.Driver");
+
+        Connection conn = DriverManager.getConnection("jdbc:h2:"+BASE_DIR+"/linked1", "sa1", "abc");
+        Statement stat = conn.createStatement();
+        stat.execute("CREATE TABLE TEST(ID INT PRIMARY KEY, NAME VARCHAR)");
+        
+        Connection conn2 = DriverManager.getConnection("jdbc:h2:"+BASE_DIR+"/linked2", "sa2", "def");
+        Statement stat2 = conn2.createStatement();
+        String link = "CREATE LINKED TABLE TEST_LINK_U('', 'jdbc:h2:"+BASE_DIR+"/linked1', 'sa1', 'abc', 'TEST') EMIT UPDATES";
+        stat2.execute(link);
+        link = "CREATE LINKED TABLE TEST_LINK_DI('', 'jdbc:h2:"+BASE_DIR+"/linked1', 'sa1', 'abc', 'TEST')";
+        stat2.execute(link);
+        stat2.executeUpdate("INSERT INTO TEST_LINK_U VALUES(1, 'Hello')");
+        stat2.executeUpdate("INSERT INTO TEST_LINK_DI VALUES(2, 'World')");
+        try {
+            stat2.executeUpdate("UPDATE TEST_LINK_U SET ID=ID+1");
+            error("unexpected success");
+        } catch(SQLException e) {
+            checkNotGeneralException(e);
+        }
+        stat2.executeUpdate("UPDATE TEST_LINK_DI SET ID=ID+1");
+        stat2.executeUpdate("UPDATE TEST_LINK_U SET NAME=NAME || ID");
+        ResultSet rs;
+        rs = stat.executeQuery("SELECT * FROM TEST ORDER BY ID");
+        rs.next();
+        check(rs.getInt(1), 2);
+        check(rs.getString(2), "Hello2");
+        rs.next();
+        check(rs.getInt(1), 3);
+        check(rs.getString(2), "World3");
+        checkFalse(rs.next());
+        
+        conn.close();
+        conn2.close();
+    }
+    
     private void testLinkSchema() throws Exception {
         deleteDb("linked1");
         deleteDb("linked2");