add TruncateTableSuite test

src/it/scala/net/snowflake/spark/snowflake/TruncateTableSuite.scala

@@ -0,0 +1,223 @@
+package net.snowflake.spark.snowflake
+
+import net.snowflake.spark.snowflake.Utils.SNOWFLAKE_SOURCE_NAME
+import org.apache.spark.sql.types._
+import org.apache.spark.sql.{Row, SaveMode}
+
+import scala.util.Random
+
+class TruncateTableSuite extends IntegrationSuiteBase{
+  val table = s"test_table_$randomSuffix"
+
+  lazy val st1 = new StructType(
+    Array(
+      StructField("num1", LongType, nullable = false),
+      StructField("num2", FloatType, nullable = false)
+    )
+  )
+
+  lazy val df1 = sqlContext.createDataFrame(
+    sc.parallelize(1 to 100).map[Row](
+      _ => {
+        val rand = new Random(System.nanoTime())
+        Row(rand.nextLong(), rand.nextFloat())
+      }
+    ),
+    st1
+  )
+
+  lazy val st2 = new StructType(
+    Array(
+      StructField("num1", IntegerType, nullable = false),
+      StructField("num2", IntegerType, nullable = false)
+    )
+  )
+
+  lazy val df2 = sqlContext.createDataFrame(
+    sc.parallelize(1 to 100).map[Row](
+      _ => {
+        val rand = new Random(System.nanoTime())
+        Row(rand.nextInt(), rand.nextInt())
+      }
+    ),
+    st2
+  )
+
+  override def beforeAll(): Unit = {
+    super.beforeAll()
+  }
+
+
+  test("use truncate table with staging table") {
+
+    jdbcUpdate(s"drop table if exists $table")
+
+    //create one table
+    df2.write.format(SNOWFLAKE_SOURCE_NAME)
+      .options(connectorOptionsNoTable)
+      .option("dbtable", table)
+      .option("truncate_table", "off")
+      .option("usestagingtable", "on")
+      .mode(SaveMode.Overwrite)
+      .save()
+
+    //replace previous table and overwrite schema
+    df1.write.format(SNOWFLAKE_SOURCE_NAME)
+      .options(connectorOptionsNoTable)
+      .option("dbtable", table)
+      .option("truncate_table", "off")
+      .option("usestagingtable", "on")
+      .mode(SaveMode.Overwrite)
+      .save()
+
+    //truncate previous table and keep schema
+    df2.write.format(SNOWFLAKE_SOURCE_NAME)
+      .options(connectorOptionsNoTable)
+      .option("dbtable", table)
+      .option("truncate_table", "on")
+      .option("usestagingtable", "on")
+      .mode(SaveMode.Overwrite)
+      .save()
+
+    //check schema
+    assert(checkSchema1())
+
+
+
+  }
+
+  test("use truncate table without staging table") {
+
+    jdbcUpdate(s"drop table if exists $table")
+
+    //create table
+    df2.write.format(SNOWFLAKE_SOURCE_NAME)
+      .options(connectorOptionsNoTable)
+      .option("dbtable", table)
+      .option("truncate_table", "off")
+      .option("usestagingtable", "off")
+      .mode(SaveMode.Overwrite)
+      .save()
+
+    //replace previous table and overwrite schema
+    df1.write.format(SNOWFLAKE_SOURCE_NAME)
+      .options(connectorOptionsNoTable)
+      .option("dbtable", table)
+      .option("truncate_table", "off")
+      .option("usestagingtable", "off")
+      .mode(SaveMode.Overwrite)
+      .save()
+
+    //truncate table and keep schema
+    df2.write.format(SNOWFLAKE_SOURCE_NAME)
+      .options(connectorOptionsNoTable)
+      .option("dbtable", table)
+      .option("truncate_table", "on")
+      .option("usestagingtable", "off")
+      .mode(SaveMode.Overwrite)
+      .save()
+
+    //checker schema
+    assert(checkSchema1())
+
+  }
+
+  test("don't truncate table with staging table") {
+
+    jdbcUpdate(s"drop table if exists $table")
+
+    //create one table
+    df2.write.format(SNOWFLAKE_SOURCE_NAME)
+      .options(connectorOptionsNoTable)
+      .option("dbtable", table)
+      .option("truncate_table", "off")
+      .option("usestagingtable", "on")
+      .mode(SaveMode.Overwrite)
+      .save()
+
+    //replace previous table and overwrite schema
+    df1.write.format(SNOWFLAKE_SOURCE_NAME)
+      .options(connectorOptionsNoTable)
+      .option("dbtable", table)
+      .option("truncate_table", "off")
+      .option("usestagingtable", "on")
+      .mode(SaveMode.Overwrite)
+      .save()
+
+    //truncate previous table and overwrite schema
+    df2.write.format(SNOWFLAKE_SOURCE_NAME)
+      .options(connectorOptionsNoTable)
+      .option("dbtable", table)
+      .option("truncate_table", "off")
+      .option("usestagingtable", "on")
+      .mode(SaveMode.Overwrite)
+      .save()
+
+    //check schema
+    assert(checkSchema2())
+  }
+  test("don't truncate table without staging table") {
+
+    jdbcUpdate(s"drop table if exists $table")
+
+    //create one table
+    df2.write.format(SNOWFLAKE_SOURCE_NAME)
+      .options(connectorOptionsNoTable)
+      .option("dbtable", table)
+      .option("truncate_table", "off")
+      .option("usestagingtable", "off")
+      .mode(SaveMode.Overwrite)
+      .save()
+
+    //replace previous table and overwrite schema
+    df1.write.format(SNOWFLAKE_SOURCE_NAME)
+      .options(connectorOptionsNoTable)
+      .option("dbtable", table)
+      .option("truncate_table", "off")
+      .option("usestagingtable", "off")
+      .mode(SaveMode.Overwrite)
+      .save()
+
+    //truncate previous table and overwrite schema
+    df2.write.format(SNOWFLAKE_SOURCE_NAME)
+      .options(connectorOptionsNoTable)
+      .option("dbtable", table)
+      .option("truncate_table", "off")
+      .option("usestagingtable", "off")
+      .mode(SaveMode.Overwrite)
+      .save()
+
+    //check schema
+    assert(checkSchema2())
+  }
+
+  def checkSchema2(): Boolean = {
+    val st = DefaultJDBCWrapper.resolveTable(conn, table)
+    val st1 = new StructType(
+      Array(
+        StructField("NUM1", DecimalType(38, 0), nullable = false),
+        StructField("NUM2", DecimalType(38, 0), nullable = false)
+      )
+    )
+    st.equals(st1)
+  }
+
+  def checkSchema1(): Boolean = {
+    val st = DefaultJDBCWrapper.resolveTable(conn, table)
+    val st1 = new StructType(
+      Array(
+        StructField("NUM1", DecimalType(38, 0), nullable = false),
+        StructField("NUM2", DoubleType, nullable = false)
+      )
+    )
+    st.equals(st1)
+  }
+
+
+
+
+    override def afterAll(): Unit = {
+    jdbcUpdate(s"drop table if exists $table")
+    super.afterAll()
+  }
+}

src/main/scala/net/snowflake/spark/snowflake/io/StageWriter.scala

@@ -169,10 +169,10 @@ private[io] object StageWriter {
           jdbcWrapper.tableExists(conn, table.toString)){
           if(params.useStagingTable){
             if(params.truncateTable)
-              execute(s"create or replace $tempTable like $table")
+              execute(s"create or replace table $tempTable like $table")
           }
           else if(params.truncateTable) execute(s"truncate $table")
-          else execute(s"drop table is exists $table")
+          else execute(s"drop table if exists $table")
         }
 
         //create table