云原生多模数据库 Lindorm：接口说明

数据库和表管理示例

数据库和表的DDL操作主要包括创建、删除、查看等。代码示例如下：

// 1.查看数据库列表
String showDatabase = "show databases";
Result result = lindormTSDBClient.execute(showDatabase);
System.out.println("before create, db list: " +  result.getRows().stream().map(e -> (String) e.get(0)).collect(Collectors.toList()));

// 2.创建数据库，此处示例创建了名为demo的数据库
String createDatabase = "create database demo";
result = lindormTSDBClient.execute(createDatabase);
System.out.println("create database:" + result.isSuccessful());

// 3.查看数据库列表
result = lindormTSDBClient.execute(showDatabase);
System.out.println("after create, db list: " +  result.getRows().stream().map(e -> (String) e.get(0)).collect(Collectors.toList()));

String database = "demo";

// 4.查看所有表
String showTables = "show tables";
result = lindormTSDBClient.execute(database, showTables);
System.out.println("before create, table list: " +  result.getRows().stream().map(e -> (String) e.get(0)).collect(Collectors.toList()));

// 5.创建表
String createTable = "CREATE TABLE sensor (device_id VARCHAR TAG,region VARCHAR TAG,time BIGINT,temperature DOUBLE,humidity DOUBLE,PRIMARY KEY(device_id))";
result = lindormTSDBClient.execute(database, createTable);
System.out.println("create table: " + result.isSuccessful());

// 6.查看所有表，验证是否成功创建了表sensor
result = lindormTSDBClient.execute(database, showTables);
System.out.println("after create, table list: " +  result.getRows().stream().map(e -> (String) e.get(0)).collect(Collectors.toList()));

// 7.描述表详情
String describeTable = "describe table sensor";
result = lindormTSDBClient.execute(database, describeTable);
System.out.println("------------ describe table -------------------");
List<String> columns = result.getColumns();
System.out.println("columns: " + columns);
List<String> metadata = result.getMetadata();
System.out.println("metadata: " + metadata);
List<List<Object>> rows = result.getRows();
for (int i = 0, size = rows.size(); i < size; i++) {
    List<Object> row = rows.get(i);
    System.out.println("column #" + i + " : " + row);
}

System.out.println("------------ describe table -------------------");
// 8.删除表
String dropTable = "drop table sensor";
result = lindormTSDBClient.execute(database, dropTable);
System.out.println("drop table: " + result.isSuccessful());

// 9.查看表列表，验证是否成功删除
result = lindormTSDBClient.execute(database, showTables);
System.out.println("after drop, table list: " +  result.getRows().stream().map(e -> (String) e.get(0)).collect(Collectors.toList()));

// 10.删除指定数据库
String dropDatabase = "drop database demo";
result = lindormTSDBClient.execute(dropDatabase);
System.out.println("drop database:" + result.isSuccessful());

// 11.查看数据库列表，验证指定数据库是否删除成功
result = lindormTSDBClient.execute(showDatabase);
System.out.println("after drop, db list : " +  result.getRows().stream().map(e -> (String) e.get(0)).collect(Collectors.toList()));

运行结果示例：

before create, db list: [default]
create database:true
after create, db list: [default, demo]
before create, table list: []
create table: true
after create, table list: [sensor]
------------ describe table -------------------
columns: [columnName, typeName, columnKind]
metadata: [VARCHAR, VARCHAR, VARCHAR]
column #0 : [device_id, VARCHAR, TAG]
column #1 : [region, VARCHAR, TAG]
column #2 : [time, TIMESTAMP, TIMESTAMP]
column #3 : [temperature, DOUBLE, FIELD]
column #4 : [humidity, DOUBLE, FIELD]
------------ describe table -------------------
drop table: true
after drop, table list: []
drop database:true
after drop, db list : [default]

写入记录

Lindorm TSDB SDK使用Record对象表示表中的一行写入记录。Record需要指定表名、时间戳、标签和量测值。其中，时间戳和标签将用于构建索引。

默认构建Record会进行字符合法性校验，可以通过在build中添加参数'false'关闭校验。

Record record = Record
    // 指定表名
    .table("sensor")
    // 指定时间戳，单位为毫秒
    .time(currentTime)
    // 指定标签
    .tag("device_id", "F07A1260")
    .tag("region", "north-cn")
    // 指定量测值
    .addField("temperature", 12.1)
    .addField("humidity", 45.0)
    .build();

使用CompletableFuture处理写入结果的接口

• 每次只提交一行记录。

// 写入默认数据库 
CompletableFuture<WriteResult> future = lindormTSDBClient.write(record);

// 写入指定的数据库
String database = "demo";
CompletableFuture<WriteResult> future = lindormTSDBClient.write(database, record);

• 每次提交多行记录（推荐）。这种方式提交方式，可减少提交时的SDK异步队列锁竞争，效率较高。

List<Record> records;
// 写入默认数据库
CompletableFuture<WriteResult> future = lindormTSDBClient.write(records);

// 写入指定的数据库
String database = "demo";
CompletableFuture<WriteResult> future = lindormTSDBClient.write(database, records);

• 处理CompletableFuture<WriteResult>完成时的结果。这里仅是一个示例，业务上可以结合实际情况，调用CompletableFuture的其他方法进行结果处理。

CompletableFuture<WriteResult> future = lindormTSDBClient.write(records);
// 处理异步写入结果
future.whenComplete((r, ex) -> {
    if (ex != null) { // 发送异常，一般都是写入失败
        System.out.println("Failed to write.");
        Throwable throwable = ExceptionUtils.getRootCause(ex);
        if (throwable instanceof LindormTSDBException) {
            LindormTSDBException e = (LindormTSDBException) throwable;
            System.out.println("Caught an LindormTSDBException, which means your request made it to Lindorm TSDB, "
                               + "but was rejected with an error response for some reason.");
            System.out.println("Error Code: " + e.getCode());
            System.out.println("SQL State:  " + e.getSqlstate());
            System.out.println("Error Message: " + e.getMessage());
        }  else {
            throwable.printStackTrace();
        }
    } else  { // 一般都是写入成功
        if (r.isSuccessful()) {
            System.out.println("Write successfully.");
        } else {
            System.out.println("Write failure.");
        }
    }
});

使用回调函数Callback处理异步写入结果的接口

• 写入回调接口Callback的定义如下所示。onCompletion方法上的result表示写入结果，records表示这个回调函数关联的写入记录，异常e表示写入失败时的异常。

public interface Callback {
    void onCompletion(WriteResult result, List<Record> records, Throwable e);
}

下面是使用Callback接口处理写入结果的一个示例。

Callback callback =  new Callback() {
    @Override
    public void onCompletion(WriteResult result, List<Record> list,
                             Throwable throwable) {
        if (throwable != null) { // 写入失败
            if (throwable instanceof LindormTSDBException) {
                LindormTSDBException ex = (LindormTSDBException) throwable;
                System.out.println("errorCode: " + ex.getCode());
                System.out.println("sqlstate: " + ex.getSqlstate());
                System.out.println("message: " + ex.getMessage());
            } else {
                // 其他错误
                throwable.printStackTrace();
            }
        } else {
            if (result.isSuccessful()) {
                System.out.println("Write successfully.");
            } else {
                System.out.println("Write failure.");
            }
        }
    }
};

• 每次提交一行记录。

// 写入默认数据库 
lindormTSDBClient.write(record, callback);

// 写入指定的数据库
String database = "demo";
lindormTSDBClient.write(database, record, callback);

• 每次提交多行记录（推荐）。这种方式提交方式，可减少提交时的SDK异步队列锁竞争，效率较高。

List<Record> records;
// 写入默认数据库
lindormTSDBClient.write(records, callback);

// 写入指定的数据库
String database = "demo";
lindormTSDBClient.write(database, records, callback);