Parquet 檔案

peopleDF = spark.read.json("examples/src/main/resources/people.json")

# DataFrames can be saved as Parquet files, maintaining the schema information.
peopleDF.write.parquet("people.parquet")

# Read in the Parquet file created above.
# Parquet files are self-describing so the schema is preserved.
# The result of loading a parquet file is also a DataFrame.
parquetFile = spark.read.parquet("people.parquet")

# Parquet files can also be used to create a temporary view and then used in SQL statements.
parquetFile.createOrReplaceTempView("parquetFile")
teenagers = spark.sql("SELECT name FROM parquetFile WHERE age >= 13 AND age <= 19")
teenagers.show()
# +------+
# |  name|
# +------+
# |Justin|
# +------+

// Encoders for most common types are automatically provided by importing spark.implicits._
import spark.implicits._

val peopleDF = spark.read.json("examples/src/main/resources/people.json")

// DataFrames can be saved as Parquet files, maintaining the schema information
peopleDF.write.parquet("people.parquet")

// Read in the parquet file created above
// Parquet files are self-describing so the schema is preserved
// The result of loading a Parquet file is also a DataFrame
val parquetFileDF = spark.read.parquet("people.parquet")

// Parquet files can also be used to create a temporary view and then used in SQL statements
parquetFileDF.createOrReplaceTempView("parquetFile")
val namesDF = spark.sql("SELECT name FROM parquetFile WHERE age BETWEEN 13 AND 19")
namesDF.map(attributes => "Name: " + attributes(0)).show()
// +------------+
// |       value|
// +------------+
// |Name: Justin|
// +------------+

import org.apache.spark.api.java.function.MapFunction;
import org.apache.spark.sql.Encoders;
import org.apache.spark.sql.Dataset;
import org.apache.spark.sql.Row;

Dataset<Row> peopleDF = spark.read().json("examples/src/main/resources/people.json");

// DataFrames can be saved as Parquet files, maintaining the schema information
peopleDF.write().parquet("people.parquet");

// Read in the Parquet file created above.
// Parquet files are self-describing so the schema is preserved
// The result of loading a parquet file is also a DataFrame
Dataset<Row> parquetFileDF = spark.read().parquet("people.parquet");

// Parquet files can also be used to create a temporary view and then used in SQL statements
parquetFileDF.createOrReplaceTempView("parquetFile");
Dataset<Row> namesDF = spark.sql("SELECT name FROM parquetFile WHERE age BETWEEN 13 AND 19");
Dataset<String> namesDS = namesDF.map(
    (MapFunction<Row, String>) row -> "Name: " + row.getString(0),
    Encoders.STRING());
namesDS.show();
// +------------+
// |       value|
// +------------+
// |Name: Justin|
// +------------+

df <- read.df("examples/src/main/resources/people.json", "json")

# SparkDataFrame can be saved as Parquet files, maintaining the schema information.
write.parquet(df, "people.parquet")

# Read in the Parquet file created above. Parquet files are self-describing so the schema is preserved.
# The result of loading a parquet file is also a DataFrame.
parquetFile <- read.parquet("people.parquet")

# Parquet files can also be used to create a temporary view and then used in SQL statements.
createOrReplaceTempView(parquetFile, "parquetFile")
teenagers <- sql("SELECT name FROM parquetFile WHERE age >= 13 AND age <= 19")
head(teenagers)
##     name
## 1 Justin

# We can also run custom R-UDFs on Spark DataFrames. Here we prefix all the names with "Name:"
schema <- structType(structField("name", "string"))
teenNames <- dapply(df, function(p) { cbind(paste("Name:", p$name)) }, schema)
for (teenName in collect(teenNames)$name) {
  cat(teenName, "\n")
}
## Name: Michael
## Name: Andy
## Name: Justin

from pyspark.sql import Row

# spark is from the previous example.
# Create a simple DataFrame, stored into a partition directory
sc = spark.sparkContext

squaresDF = spark.createDataFrame(sc.parallelize(range(1, 6))
                                  .map(lambda i: Row(single=i, double=i ** 2)))
squaresDF.write.parquet("data/test_table/key=1")

# Create another DataFrame in a new partition directory,
# adding a new column and dropping an existing column
cubesDF = spark.createDataFrame(sc.parallelize(range(6, 11))
                                .map(lambda i: Row(single=i, triple=i ** 3)))
cubesDF.write.parquet("data/test_table/key=2")

# Read the partitioned table
mergedDF = spark.read.option("mergeSchema", "true").parquet("data/test_table")
mergedDF.printSchema()

# The final schema consists of all 3 columns in the Parquet files together
# with the partitioning column appeared in the partition directory paths.
# root
#  |-- double: long (nullable = true)
#  |-- single: long (nullable = true)
#  |-- triple: long (nullable = true)
#  |-- key: integer (nullable = true)

// This is used to implicitly convert an RDD to a DataFrame.
import spark.implicits._

// Create a simple DataFrame, store into a partition directory
val squaresDF = spark.sparkContext.makeRDD(1 to 5).map(i => (i, i * i)).toDF("value", "square")
squaresDF.write.parquet("data/test_table/key=1")

// Create another DataFrame in a new partition directory,
// adding a new column and dropping an existing column
val cubesDF = spark.sparkContext.makeRDD(6 to 10).map(i => (i, i * i * i)).toDF("value", "cube")
cubesDF.write.parquet("data/test_table/key=2")

// Read the partitioned table
val mergedDF = spark.read.option("mergeSchema", "true").parquet("data/test_table")
mergedDF.printSchema()

// The final schema consists of all 3 columns in the Parquet files together
// with the partitioning column appeared in the partition directory paths
// root
//  |-- value: int (nullable = true)
//  |-- square: int (nullable = true)
//  |-- cube: int (nullable = true)
//  |-- key: int (nullable = true)

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import org.apache.spark.sql.Dataset;
import org.apache.spark.sql.Row;

public static class Square implements Serializable {
  private int value;
  private int square;

  // Getters and setters...

}

public static class Cube implements Serializable {
  private int value;
  private int cube;

  // Getters and setters...

}

List<Square> squares = new ArrayList<>();
for (int value = 1; value <= 5; value++) {
  Square square = new Square();
  square.setValue(value);
  square.setSquare(value * value);
  squares.add(square);
}

// Create a simple DataFrame, store into a partition directory
Dataset<Row> squaresDF = spark.createDataFrame(squares, Square.class);
squaresDF.write().parquet("data/test_table/key=1");

List<Cube> cubes = new ArrayList<>();
for (int value = 6; value <= 10; value++) {
  Cube cube = new Cube();
  cube.setValue(value);
  cube.setCube(value * value * value);
  cubes.add(cube);
}

// Create another DataFrame in a new partition directory,
// adding a new column and dropping an existing column
Dataset<Row> cubesDF = spark.createDataFrame(cubes, Cube.class);
cubesDF.write().parquet("data/test_table/key=2");

// Read the partitioned table
Dataset<Row> mergedDF = spark.read().option("mergeSchema", true).parquet("data/test_table");
mergedDF.printSchema();

// The final schema consists of all 3 columns in the Parquet files together
// with the partitioning column appeared in the partition directory paths
// root
//  |-- value: int (nullable = true)
//  |-- square: int (nullable = true)
//  |-- cube: int (nullable = true)
//  |-- key: int (nullable = true)

df1 <- createDataFrame(data.frame(single=c(12, 29), double=c(19, 23)))
df2 <- createDataFrame(data.frame(double=c(19, 23), triple=c(23, 18)))

# Create a simple DataFrame, stored into a partition directory
write.df(df1, "data/test_table/key=1", "parquet", "overwrite")

# Create another DataFrame in a new partition directory,
# adding a new column and dropping an existing column
write.df(df2, "data/test_table/key=2", "parquet", "overwrite")

# Read the partitioned table
df3 <- read.df("data/test_table", "parquet", mergeSchema = "true")
printSchema(df3)
# The final schema consists of all 3 columns in the Parquet files together
# with the partitioning column appeared in the partition directory paths
## root
##  |-- single: double (nullable = true)
##  |-- double: double (nullable = true)
##  |-- triple: double (nullable = true)
##  |-- key: integer (nullable = true)