Lindorm：介面說明

資料庫和表管理樣本

資料庫和表的DDL操作主要包括建立、刪除、查看等。程式碼範例如下：

// 1.查看資料庫列表
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.建立資料庫，此處樣本建立了名為demo的資料庫
String createDatabase = "create database demo";
result = lindormTSDBClient.execute(createDatabase);
System.out.println("create database:" + result.isSuccessful());

// 3.查看資料庫列表
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.建立表
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，驗證是否成功建立了表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.描述表詳情
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.刪除表
String dropTable = "drop table sensor";
result = lindormTSDBClient.execute(database, dropTable);
System.out.println("drop table: " + result.isSuccessful());

// 9.查看錶列表，驗證是否成功刪除
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.刪除指定資料庫
String dropDatabase = "drop database demo";
result = lindormTSDBClient.execute(dropDatabase);
System.out.println("drop database:" + result.isSuccessful());

// 11.查看資料庫列表，驗證指定資料庫是否刪除成功
result = lindormTSDBClient.execute(showDatabase);
System.out.println("after drop, db list : " +  result.getRows().stream().map(e -> (String) e.get(0)).collect(Collectors.toList()));

運行結果樣本：

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]

寫入記錄

Lindorm TSDB SDK使用Record對象表示表中的一行寫入記錄。Record需要指定表名、時間戳記、標籤和量測值。其中，時間戳記和標籤將用於構建索引。

預設構建Record會進行字元合法性校正，可以通過在build中添加參數'false'關閉校正。

Record record = Record
    // 指定表名
    .table("sensor")
    // 指定時間戳記，單位為毫秒
    .time(currentTime)
    // 指定標籤
    .tag("device_id", "F07A1260")
    .tag("region", "north-cn")
    // 指定量測值
    .addField("temperature", 12.1)
    .addField("humidity", 45.0)
    .build();

使用CompletableFuture處理寫入結果的介面

• 每次只提交一行記錄。

// 寫入預設資料庫 
CompletableFuture<WriteResult> future = lindormTSDBClient.write(record);

// 寫入指定的資料庫
String database = "demo";
CompletableFuture<WriteResult> future = lindormTSDBClient.write(database, record);

• 每次提交多行記錄（推薦）。這種方式提交方式，可減少提交時的SDK非同步隊列鎖競爭，效率較高。

List<Record> records;
// 寫入預設資料庫
CompletableFuture<WriteResult> future = lindormTSDBClient.write(records);

// 寫入指定的資料庫
String database = "demo";
CompletableFuture<WriteResult> future = lindormTSDBClient.write(database, records);

• 處理CompletableFuture<WriteResult>完成時的結果。這裡僅是一個樣本，業務上可以結合實際情況，調用CompletableFuture的其他方法進行結果處理。

CompletableFuture<WriteResult> future = lindormTSDBClient.write(records);
// 處理非同步寫入結果
future.whenComplete((r, ex) -> {
    if (ex != null) { // 發送異常，一般都是寫入失敗
        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  { // 一般都是寫入成功
        if (r.isSuccessful()) {
            System.out.println("Write successfully.");
        } else {
            System.out.println("Write failure.");
        }
    }
});

使用回呼函數Callback處理非同步寫入結果的介面

• 寫入回調介面Callback的定義如下所示。onCompletion方法上的result表示寫入結果，records表示這個回呼函數關聯的寫入記錄，異常e表示寫入失敗時的異常。

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

下面是使用Callback介面處理寫入結果的一個樣本。

Callback callback =  new Callback() {
    @Override
    public void onCompletion(WriteResult result, List<Record> list,
                             Throwable throwable) {
        if (throwable != null) { // 寫入失敗
            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 {
                // 其他錯誤
                throwable.printStackTrace();
            }
        } else {
            if (result.isSuccessful()) {
                System.out.println("Write successfully.");
            } else {
                System.out.println("Write failure.");
            }
        }
    }
};

• 每次提交一行記錄。

// 寫入預設資料庫 
lindormTSDBClient.write(record, callback);

// 寫入指定的資料庫
String database = "demo";
lindormTSDBClient.write(database, record, callback);

• 每次提交多行記錄（推薦）。這種方式提交方式，可減少提交時的SDK非同步隊列鎖競爭，效率較高。

List<Record> records;
// 寫入預設資料庫
lindormTSDBClient.write(records, callback);

// 寫入指定的資料庫
String database = "demo";
lindormTSDBClient.write(database, records, callback);