object CatalogApiTest {

  def main(args: Array[String]): Unit = {

    val spark = SparkSession

      .builder()

      .appName("CatalogApiTest")

      .getOrCreate()

    //查看spark sql应用用的是哪一种catalog

    //目前支持hive metastore 和in-memory两种

    //spark-shell默认的值为hive

    //spark-shell --master spark://master:7077 --conf spark.sql.catalogImplementation=in-memory

    spark.conf.get("spark.sql.catalogImplementation")

    //1：数据库元数据信息

    spark.catalog.listDatabases().show(false)

    spark.catalog.currentDatabase

    val db = spark.catalog.getDatabase("default")

    spark.catalog.databaseExists("twq")

    spark.sql("CREATE DATABASE IF NOT EXISTS twq " +

      "COMMENT 'Test database' LOCATION 'hdfs://master:9999/user/hadoop-twq/spark-db'")

    spark.catalog.setCurrentDatabase("twq")

    spark.catalog.currentDatabase

    //2：表元数据相关信息

    spark.catalog.listTables("twq").show()

    val sessionDf = spark.read.parquet(s"${BASE_PATH}/trackerSession")

    //创建一张表

    sessionDf.createOrReplaceTempView("trackerSession")

    //catalog table相关元数据操作

    spark.catalog.listTables("twq").show()

    //用sql的方式查询表

    val sessionRecords = spark.sql("select * from trackerSession")

    sessionRecords.show()

    spark.catalog.tableExists("log")

    spark.catalog.tableExists("trackerSession")

    spark.catalog.tableExists("twq", "trackerSession") //todo 感觉应该是spark的bug

    spark.catalog.listTables("twq").show()

    spark.catalog.getTable("trackerSession")

    //表的缓存

    spark.catalog.cacheTable("trackerSession")

    spark.catalog.uncacheTable("trackerSession")

    //3：表的列的元数据信息

    spark.catalog.listColumns("trackerSession").show()

    spark.sql("drop table trackerSession")

    spark.sql("drop database twq")

    spark.catalog.setCurrentDatabase("default")

    spark.catalog.listTables().show()

    spark.stop()

  }

}