使用列判斷條件更新數據

• 構造SingleColumnValueCondition。

  以下示例用于當數據滿足Col0==0條件時，更新Col0列值。

  private static void updateRowWithSingleColumnValueCondition(SyncClient client, String pkValue){
      //構造主鍵。
      PrimaryKeyBuilder primaryKeyBuilder = PrimaryKeyBuilder.createPrimaryKeyBuilder();
      primaryKeyBuilder.addPrimaryKeyColumn("pk", PrimaryKeyValue.fromString(pkValue));
      PrimaryKey primaryKey = primaryKeyBuilder.build();
      
      //讀取一行數據。
      SingleRowQueryCriteria criteria = new SingleRowQueryCriteria("<TABLE_NAME>", primaryKey);
      criteria.setMaxVersions(1);
      GetRowResponse getRowResponse = client.getRow(new GetRowRequest(criteria));
      Row row = getRowResponse.getRow();
      long col0Value = row.getLatestColumn("Col0").getValue().asLong();
  
      //設置數據表名稱。
      RowUpdateChange rowUpdateChange = new RowUpdateChange("<TABLE_NAME>", primaryKey);
  
      //設置條件為Col0==0。
      SingleColumnValueCondition singleColumnValueCondition = new SingleColumnValueCondition("Col0",
              SingleColumnValueCondition.CompareOperator.EQUAL, ColumnValue.fromLong(0));
      //如果不存在Col0列，條件檢查不通過。
      singleColumnValueCondition.setPassIfMissing(false);
      //只判斷最新版本。
      singleColumnValueCondition.setLatestVersionsOnly(true);
      Condition condition = new Condition();
      condition.setColumnCondition(singleColumnValueCondition);
      rowUpdateChange.setCondition(condition);
      //當數據滿足列判斷條件時，更新Col0列值，使Col0列值增加1。
      rowUpdateChange.put(new Column("Col0", ColumnValue.fromLong(col0Value+1)));
      try {
          client.updateRow(new UpdateRowRequest(rowUpdateChange));
          System.out.println("數據更新成功！");
      } catch (TableStoreException ex) {
          System.out.println("數據更新失敗！" + ex.toString());
      }
  }                 

• 構造CompositeColumnValueCondition。

  以下示例用于當數據滿足Col0 == 0且Col1 > 100或者Col2 <= 10中任意一個條件時，更新Col0列值。

  private static void updateRowWithCompositeColumnValueCondition(SyncClient client, String pkValue){
      //構造主鍵。
      PrimaryKeyBuilder primaryKeyBuilder = PrimaryKeyBuilder.createPrimaryKeyBuilder();
      primaryKeyBuilder.addPrimaryKeyColumn("pk", PrimaryKeyValue.fromString(pkValue));
      PrimaryKey primaryKey = primaryKeyBuilder.build();
          
  		//讀取一行數據。
      SingleRowQueryCriteria criteria = new SingleRowQueryCriteria("<TABLE_NAME>", primaryKey);
      criteria.setMaxVersions(1);
      GetRowResponse getRowResponse = client.getRow(new GetRowRequest(criteria));
      Row row = getRowResponse.getRow();
      long col0Value = row.getLatestColumn("Col0").getValue().asLong();
  
      //設置數據表名稱。
      RowUpdateChange rowUpdateChange = new RowUpdateChange("<TABLE_NAME>", primaryKey);
  
      //composite1的條件為(Col0 == 0) AND (Col1 > 100)。
      CompositeColumnValueCondition composite1 = new CompositeColumnValueCondition(CompositeColumnValueCondition.LogicOperator.AND);
      SingleColumnValueCondition single1 = new SingleColumnValueCondition("Col0",
              SingleColumnValueCondition.CompareOperator.EQUAL, ColumnValue.fromLong(0));
      SingleColumnValueCondition single2 = new SingleColumnValueCondition("Col1",
              SingleColumnValueCondition.CompareOperator.GREATER_THAN, ColumnValue.fromLong(100));
      composite1.addCondition(single1);
      composite1.addCondition(single2);
  
      //composite2的條件為((Col0 == 0) AND (Col1 > 100)) OR (Col2 <= 10)。
      CompositeColumnValueCondition composite2 = new CompositeColumnValueCondition(CompositeColumnValueCondition.LogicOperator.OR);
      SingleColumnValueCondition single3 = new SingleColumnValueCondition("Col2",
              SingleColumnValueCondition.CompareOperator.LESS_EQUAL, ColumnValue.fromLong(10));
      composite2.addCondition(composite1);
      composite2.addCondition(single3);
  
      Condition condition = new Condition();
      condition.setColumnCondition(composite2);
      rowUpdateChange.setCondition(condition);
  		//當數據滿足列判斷條件時，更新Col0列值，使Col0列值增加1。
      rowUpdateChange.put(new Column("Col0", ColumnValue.fromLong(col0Value+1)));
      try {
          client.updateRow(new UpdateRowRequest(rowUpdateChange));
          System.out.println("數據更新成功！");
      } catch (TableStoreException ex) {
          System.out.println("數據更新失敗！" + ex.toString());
      }
  }

使用樂觀鎖更新數據

通過Condition實現樂觀鎖機制，遞增一列。

 private static void updateRowWithCondition(SyncClient client, String pkValue) {
     //構造主鍵。
     PrimaryKeyBuilder primaryKeyBuilder = PrimaryKeyBuilder.createPrimaryKeyBuilder();
     primaryKeyBuilder.addPrimaryKeyColumn("pk", PrimaryKeyValue.fromString(pkValue));
     PrimaryKey primaryKey = primaryKeyBuilder.build();

     //讀取一行數據。
     SingleRowQueryCriteria criteria = new SingleRowQueryCriteria("<TABLE_NAME>", primaryKey);
     criteria.setMaxVersions(1);
     GetRowResponse getRowResponse = client.getRow(new GetRowRequest(criteria));
     Row row = getRowResponse.getRow();
     long col0Value = row.getLatestColumn("Col0").getValue().asLong();

     //條件更新Col0列，使列值加1。
     RowUpdateChange rowUpdateChange = new RowUpdateChange("<TABLE_NAME>", primaryKey);
     Condition condition = new Condition(RowExistenceExpectation.EXPECT_EXIST);
     ColumnCondition columnCondition = new SingleColumnValueCondition("Col0", SingleColumnValueCondition.CompareOperator.EQUAL, ColumnValue.fromLong(col0Value));
     condition.setColumnCondition(columnCondition);
     rowUpdateChange.setCondition(condition);
     rowUpdateChange.put(new Column("Col0", ColumnValue.fromLong(col0Value + 1)));

     try {
         client.updateRow(new UpdateRowRequest(rowUpdateChange));
     } catch (TableStoreException ex) {
         System.out.println(ex.toString());
     }
 }