Returns a new Dataset with an alias set.

Returns a new Dataset where each record has been mapped on to the specified type. The method used to map columns depend on the type of U:

• When U is a class, fields for the class will be mapped to columns of the same name (case sensitivity is determined by spark.sql.caseSensitive).
• When U is a tuple, the columns will be mapped by ordinal (i.e. the first column will be assigned to _1).
• When U is a primitive type (i.e. String, Int, etc), then the first column of the DataFrame will be used.

If the schema of the Dataset does not match the desired U type, you can use select along with alias or as to rearrange or rename as required.

Note that as[] only changes the view of the data that is passed into typed operations, such as map(), and does not eagerly project away any columns that are not present in the specified class.

Persist this Dataset with the default storage level (MEMORY_AND_DISK).

Returns a checkpointed version of this Dataset.

Returns a new Dataset that has exactly numPartitions partitions, when the fewer partitions are requested. If a larger number of partitions is requested, it will stay at the current number of partitions. Similar to coalesce defined on an RDD, this operation results in a narrow dependency, e.g. if you go from 1000 partitions to 100 partitions, there will not be a shuffle, instead each of the 100 new partitions will claim 10 of the current partitions.

However, if you're doing a drastic coalesce, e.g. to numPartitions = 1, this may result in your computation taking place on fewer nodes than you like (e.g. one node in the case of numPartitions = 1). To avoid this, you can call repartition. This will add a shuffle step, but means the current upstream partitions will be executed in parallel (per whatever the current partitioning is).

Selects column based on the column name and returns it as a org.apache.spark.sql.Column.

Selects column based on the column name specified as a regex and returns it as org.apache.spark.sql.Column.

Returns an array that contains all rows in this Dataset.

Running collect requires moving all the data into the application's driver process, and doing so on a very large dataset can crash the driver process with OutOfMemoryError.

For Java API, use collectAsList.

Returns a Java list that contains all rows in this Dataset.

Running collect requires moving all the data into the application's driver process, and doing so on a very large dataset can crash the driver process with OutOfMemoryError.

Returns the number of rows in the Dataset.

Explicit cartesian join with another DataFrame.

Create a multi-dimensional cube for the current Dataset using the specified columns, so we can run aggregation on them. See RelationalGroupedDataset for all the available aggregate functions.

// Compute the average for all numeric columns cubed by department and group.
ds.cube($"department", $"group").avg()

// Compute the max age and average salary, cubed by department and gender.
ds.cube($"department", $"gender").agg(Map(
  "salary" -> "avg",
  "age" -> "max"
))

Computes basic statistics for numeric and string columns, including count, mean, stddev, min, and max. If no columns are given, this function computes statistics for all numerical or string columns.

This function is meant for exploratory data analysis, as we make no guarantee about the backward compatibility of the schema of the resulting Dataset. If you want to programmatically compute summary statistics, use the agg function instead.

ds.describe("age", "height").show()

// output:
// summary age   height
// count   10.0  10.0
// mean    53.3  178.05
// stddev  11.6  15.7
// min     18.0  163.0
// max     92.0  192.0

Use summary for expanded statistics and control over which statistics to compute.

Returns a new Dataset with columns dropped.

This method can only be used to drop top level columns. This is a no-op if the Dataset doesn't have a columns with an equivalent expression.

Returns a new Dataset with columns dropped. This is a no-op if schema doesn't contain column name(s).

This method can only be used to drop top level columns. the colName string is treated literally without further interpretation.

(Scala-specific) Returns a new Dataset with duplicate rows removed, considering only the subset of columns.

For a static batch Dataset, it just drops duplicate rows. For a streaming Dataset, it will keep all data across triggers as intermediate state to drop duplicates rows. You can use withWatermark to limit how late the duplicate data can be and system will accordingly limit the state. In addition, too late data older than watermark will be dropped to avoid any possibility of duplicates.

Returns a new Dataset that contains only the unique rows from this Dataset. This is an alias for distinct.

For a static batch Dataset, it just drops duplicate rows. For a streaming Dataset, it will keep all data across triggers as intermediate state to drop duplicates rows. You can use withWatermark to limit how late the duplicate data can be and system will accordingly limit the state. In addition, too late data older than watermark will be dropped to avoid any possibility of duplicates.

Returns a new Dataset with duplicates rows removed, considering only the subset of columns, within watermark.

This only works with streaming Dataset, and watermark for the input Dataset must be set via withWatermark.

For a streaming Dataset, this will keep all data across triggers as intermediate state to drop duplicated rows. The state will be kept to guarantee the semantic, "Events are deduplicated as long as the time distance of earliest and latest events are smaller than the delay threshold of watermark." Users are encouraged to set the delay threshold of watermark longer than max timestamp differences among duplicated events.

Note: too late data older than watermark will be dropped.

Returns a new Dataset with duplicates rows removed, within watermark.

This only works with streaming Dataset, and watermark for the input Dataset must be set via withWatermark.

For a streaming Dataset, this will keep all data across triggers as intermediate state to drop duplicated rows. The state will be kept to guarantee the semantic, "Events are deduplicated as long as the time distance of earliest and latest events are smaller than the delay threshold of watermark." Users are encouraged to set the delay threshold of watermark longer than max timestamp differences among duplicated events.

Note: too late data older than watermark will be dropped.

Returns a new Dataset containing rows in this Dataset but not in another Dataset. This is equivalent to EXCEPT DISTINCT in SQL.

Returns a new Dataset containing rows in this Dataset but not in another Dataset while preserving the duplicates. This is equivalent to EXCEPT ALL in SQL.

Prints the plans (logical and physical) with a format specified by a given explain mode.

(Java-specific) Returns a new Dataset that only contains elements where func returns true.

(Scala-specific) Returns a new Dataset that only contains elements where func returns true.

Filters rows using the given condition.

// The following are equivalent:
peopleDs.filter($"age" > 15)
peopleDs.where($"age" > 15)

Applies a function f to each partition of this Dataset.

Groups the Dataset using the specified columns, so we can run aggregation on them. See RelationalGroupedDataset for all the available aggregate functions.

// Compute the average for all numeric columns grouped by department.
ds.groupBy($"department").avg()

// Compute the max age and average salary, grouped by department and gender.
ds.groupBy($"department", $"gender").agg(Map(
  "salary" -> "avg",
  "age" -> "max"
))

Create multi-dimensional aggregation for the current Dataset using the specified grouping sets, so we can run aggregation on them. See RelationalGroupedDataset for all the available aggregate functions.

// Compute the average for all numeric columns group by specific grouping sets.
ds.groupingSets(Seq(Seq($"department", $"group"), Seq()), $"department", $"group").avg()

// Compute the max age and average salary, group by specific grouping sets.
ds.groupingSets(Seq($"department", $"gender"), Seq()), $"department", $"group").agg(Map(
  "salary" -> "avg",
  "age" -> "max"
))

Returns the first n rows.

Specifies some hint on the current Dataset. As an example, the following code specifies that one of the plan can be broadcasted:

df1.join(df2.hint("broadcast"))

the following code specifies that this dataset could be rebalanced with given number of partitions:

df1.hint("rebalance", 10)

Returns a best-effort snapshot of the files that compose this Dataset. This method simply asks each constituent BaseRelation for its respective files and takes the union of all results. Depending on the source relations, this may not find all input files. Duplicates are removed.

Returns a new Dataset containing rows only in both this Dataset and another Dataset. This is equivalent to INTERSECT in SQL.

Returns a new Dataset containing rows only in both this Dataset and another Dataset while preserving the duplicates. This is equivalent to INTERSECT ALL in SQL.

Returns true if the Dataset is empty.

Returns true if the collect and take methods can be run locally (without any Spark executors).

Returns true if this Dataset contains one or more sources that continuously return data as it arrives. A Dataset that reads data from a streaming source must be executed as a StreamingQuery using the start() method in DataStreamWriter. Methods that return a single answer, e.g. count() or collect(), will throw an org.apache.spark.sql.AnalysisException when there is a streaming source present.

Join with another DataFrame, using the given join expression. The following performs a full outer join between df1 and df2.

// Scala:
import org.apache.spark.sql.functions._
df1.join(df2, $"df1Key" === $"df2Key", "outer")

// Java:
import static org.apache.spark.sql.functions.*;
df1.join(df2, col("df1Key").equalTo(col("df2Key")), "outer");

(Scala-specific) Equi-join with another DataFrame using the given columns. A cross join with a predicate is specified as an inner join. If you would explicitly like to perform a cross join use the crossJoin method.

Different from other join functions, the join columns will only appear once in the output, i.e. similar to SQL's JOIN USING syntax.

Join with another DataFrame.

Behaves as an INNER JOIN and requires a subsequent join predicate.

Joins this Dataset returning a Tuple2 for each pair where condition evaluates to true.

This is similar to the relation join function with one important difference in the result schema. Since joinWith preserves objects present on either side of the join, the result schema is similarly nested into a tuple under the column names _1 and _2.

This type of join can be useful both for preserving type-safety with the original object types as well as working with relational data where either side of the join has column names in common.

Returns a new Dataset by taking the first n rows. The difference between this function and head is that head is an action and returns an array (by triggering query execution) while limit returns a new Dataset.

(Java-specific) Returns a new Dataset that contains the result of applying func to each element.

(Scala-specific) Returns a new Dataset that contains the result of applying func to each element.

(Scala-specific) Returns a new Dataset that contains the result of applying func to each partition.

Merges a set of updates, insertions, and deletions based on a source table into a target table.

Scala Examples:

spark.table("source")
  .mergeInto("target", $"source.id" === $"target.id")
  .whenMatched($"salary" === 100)
  .delete()
  .whenNotMatched()
  .insertAll()
  .whenNotMatchedBySource($"salary" === 100)
  .update(Map(
    "salary" -> lit(200)
  ))
  .merge()

Selects a metadata column based on its logical column name, and returns it as a org.apache.spark.sql.Column.

A metadata column can be accessed this way even if the underlying data source defines a data column with a conflicting name.

Returns a DataFrameNaFunctions for working with missing data.

// Dropping rows containing any null values.
ds.na.drop()

Observe (named) metrics through an org.apache.spark.sql.Observation instance. This method does not support streaming datasets.

A user can retrieve the metrics by accessing org.apache.spark.sql.Observation.get.

// Observe row count (rows) and highest id (maxid) in the Dataset while writing it
val observation = Observation("my_metrics")
val observed_ds = ds.observe(observation, count(lit(1)).as("rows"), max($"id").as("maxid"))
observed_ds.write.parquet("ds.parquet")
val metrics = observation.get

Define (named) metrics to observe on the Dataset. This method returns an 'observed' Dataset that returns the same result as the input, with the following guarantees:

• It will compute the defined aggregates (metrics) on all the data that is flowing through the Dataset at that point.
• It will report the value of the defined aggregate columns as soon as we reach a completion point. A completion point is either the end of a query (batch mode) or the end of a streaming epoch. The value of the aggregates only reflects the data processed since the previous completion point. Please note that continuous execution is currently not supported.

The metrics columns must either contain a literal (e.g. lit(42)), or should contain one or more aggregate functions (e.g. sum(a) or sum(a + b) + avg(c) - lit(1)). Expressions that contain references to the input Dataset's columns must always be wrapped in an aggregate function.

Returns a new Dataset by skipping the first n rows.

Persist this Dataset with the given storage level.

Persist this Dataset with the default storage level (MEMORY_AND_DISK).

Randomly splits this Dataset with the provided weights.

Randomly splits this Dataset with the provided weights.

Returns a Java list that contains randomly split Dataset with the provided weights.

(Scala-specific) Reduces the elements of this Dataset using the specified binary function. The given func must be commutative and associative or the result may be non-deterministic.

Returns a new Dataset that has exactly numPartitions partitions.

Create a multi-dimensional rollup for the current Dataset using the specified columns, so we can run aggregation on them. See RelationalGroupedDataset for all the available aggregate functions.

// Compute the average for all numeric columns rolled up by department and group.
ds.rollup($"department", $"group").avg()

// Compute the max age and average salary, rolled up by department and gender.
ds.rollup($"department", $"gender").agg(Map(
  "salary" -> "avg",
  "age" -> "max"
))

Returns true when the logical query plans inside both Datasets are equal and therefore return same results.

Returns a new Dataset by sampling a fraction of rows, using a user-supplied seed.

Returns the schema of this Dataset.

Returns a new Dataset by computing the given org.apache.spark.sql.Column expression for each element.

val ds = Seq(1, 2, 3).toDS()
val newDS = ds.select(expr("value + 1").as[Int])

Selects a set of column based expressions.

ds.select($"colA", $"colB" + 1)

Internal helper function for building typed selects that return tuples. For simplicity and code reuse, we do this without the help of the type system and then use helper functions that cast appropriately for the user facing interface.

Returns a hashCode of the logical query plan against this Dataset.

Displays the Dataset in a tabular form. For example:

year  month AVG('Adj Close) MAX('Adj Close)
1980  12    0.503218        0.595103
1981  01    0.523289        0.570307
1982  02    0.436504        0.475256
1983  03    0.410516        0.442194
1984  04    0.450090        0.483521

If vertical enabled, this command prints output rows vertically (one line per column value)?

-RECORD 0-------------------
 year            | 1980
 month           | 12
 AVG('Adj Close) | 0.503218
 AVG('Adj Close) | 0.595103
-RECORD 1-------------------
 year            | 1981
 month           | 01
 AVG('Adj Close) | 0.523289
 AVG('Adj Close) | 0.570307
-RECORD 2-------------------
 year            | 1982
 month           | 02
 AVG('Adj Close) | 0.436504
 AVG('Adj Close) | 0.475256
-RECORD 3-------------------
 year            | 1983
 month           | 03
 AVG('Adj Close) | 0.410516
 AVG('Adj Close) | 0.442194
-RECORD 4-------------------
 year            | 1984
 month           | 04
 AVG('Adj Close) | 0.450090
 AVG('Adj Close) | 0.483521

Displays the Dataset in a tabular form. For example:

year  month AVG('Adj Close) MAX('Adj Close)
1980  12    0.503218        0.595103
1981  01    0.523289        0.570307
1982  02    0.436504        0.475256
1983  03    0.410516        0.442194
1984  04    0.450090        0.483521

Returns a DataFrameStatFunctions for working statistic functions support.

// Finding frequent items in column with name 'a'.
ds.stat.freqItems(Seq("a"))

Get the Dataset's current storage level, or StorageLevel.NONE if not persisted.

Computes specified statistics for numeric and string columns. Available statistics are:

• count
• mean
• stddev
• min
• max
• arbitrary approximate percentiles specified as a percentage (e.g. 75%)
• count_distinct
• approx_count_distinct

If no statistics are given, this function computes count, mean, stddev, min, approximate quartiles (percentiles at 25%, 50%, and 75%), and max.

This function is meant for exploratory data analysis, as we make no guarantee about the backward compatibility of the schema of the resulting Dataset. If you want to programmatically compute summary statistics, use the agg function instead.

ds.summary().show()

// output:
// summary age   height
// count   10.0  10.0
// mean    53.3  178.05
// stddev  11.6  15.7
// min     18.0  163.0
// 25%     24.0  176.0
// 50%     24.0  176.0
// 75%     32.0  180.0
// max     92.0  192.0

ds.summary("count", "min", "25%", "75%", "max").show()

// output:
// summary age   height
// count   10.0  10.0
// min     18.0  163.0
// 25%     24.0  176.0
// 75%     32.0  180.0
// max     92.0  192.0

To do a summary for specific columns first select them:

ds.select("age", "height").summary().show()

Specify statistics to output custom summaries:

ds.summary("count", "count_distinct").show()

The distinct count isn't included by default.

You can also run approximate distinct counts which are faster:

ds.summary("count", "approx_count_distinct").show()

See also describe for basic statistics.

Returns the last n rows in the Dataset.

Running tail requires moving data into the application's driver process, and doing so with a very large n can crash the driver process with OutOfMemoryError.

Returns a new DataFrame where each row is reconciled to match the specified schema. Spark will:

• Reorder columns and/or inner fields by name to match the specified schema.
• Project away columns and/or inner fields that are not needed by the specified schema. Missing columns and/or inner fields (present in the specified schema but not input DataFrame) lead to failures.
• Cast the columns and/or inner fields to match the data types in the specified schema, if the types are compatible, e.g., numeric to numeric (error if overflows), but not string to int.
• Carry over the metadata from the specified schema, while the columns and/or inner fields still keep their own metadata if not overwritten by the specified schema.
• Fail if the nullability is not compatible. For example, the column and/or inner field is nullable but the specified schema requires them to be not nullable.

Converts this strongly typed collection of data to generic DataFrame with columns renamed. This can be quite convenient in conversion from an RDD of tuples into a DataFrame with meaningful names. For example:

val rdd: RDD[(Int, String)] = ...
rdd.toDF()  // this implicit conversion creates a DataFrame with column name `_1` and `_2`
rdd.toDF("id", "name")  // this creates a DataFrame with column name "id" and "name"

Converts this strongly typed collection of data to generic Dataframe. In contrast to the strongly typed objects that Dataset operations work on, a Dataframe returns generic org.apache.spark.sql.Row objects that allow fields to be accessed by ordinal or name.

Returns the content of the Dataset as a Dataset of JSON strings.

Returns an iterator that contains all rows in this Dataset.

The iterator will consume as much memory as the largest partition in this Dataset.

Transposes a DataFrame, switching rows to columns. This function transforms the DataFrame such that the values in the first column become the new columns of the DataFrame.

This is equivalent to calling Dataset#transpose(Column) where indexColumn is set to the first column.

Please note:

• All columns except the index column must share a least common data type. Unless they are the same data type, all columns are cast to the nearest common data type.
• The name of the column into which the original column names are transposed defaults to "key".
• Non-"key" column names for the transposed table are ordered in ascending order.

Transposes a DataFrame such that the values in the specified index column become the new columns of the DataFrame.

Please note:

• All columns except the index column must share a least common data type. Unless they are the same data type, all columns are cast to the nearest common data type.
• The name of the column into which the original column names are transposed defaults to "key".
• null values in the index column are excluded from the column names for the transposed table, which are ordered in ascending order.

val df = Seq(("A", 1, 2), ("B", 3, 4)).toDF("id", "val1", "val2")
df.show()
// output:
// +---+----+----+
// | id|val1|val2|
// +---+----+----+
// |  A|   1|   2|
// |  B|   3|   4|
// +---+----+----+

df.transpose($"id").show()
// output:
// +----+---+---+
// | key|  A|  B|
// +----+---+---+
// |val1|  1|  3|
// |val2|  2|  4|
// +----+---+---+
// schema:
// root
//  |-- key: string (nullable = false)
//  |-- A: integer (nullable = true)
//  |-- B: integer (nullable = true)

df.transpose().show()
// output:
// +----+---+---+
// | key|  A|  B|
// +----+---+---+
// |val1|  1|  3|
// |val2|  2|  4|
// +----+---+---+
// schema:
// root
//  |-- key: string (nullable = false)
//  |-- A: integer (nullable = true)
//  |-- B: integer (nullable = true)

Returns a new Dataset containing union of rows in this Dataset and another Dataset.

This is equivalent to UNION ALL in SQL. To do a SQL-style set union (that does deduplication of elements), use this function followed by a distinct.

Also as standard in SQL, this function resolves columns by position (not by name):

val df1 = Seq((1, 2, 3)).toDF("col0", "col1", "col2")
val df2 = Seq((4, 5, 6)).toDF("col1", "col2", "col0")
df1.union(df2).show

// output:
// +----+----+----+
// |col0|col1|col2|
// +----+----+----+
// |   1|   2|   3|
// |   4|   5|   6|
// +----+----+----+

Notice that the column positions in the schema aren't necessarily matched with the fields in the strongly typed objects in a Dataset. This function resolves columns by their positions in the schema, not the fields in the strongly typed objects. Use unionByName to resolve columns by field name in the typed objects.

Returns a new Dataset containing union of rows in this Dataset and another Dataset.

The difference between this function and union is that this function resolves columns by name (not by position).

When the parameter allowMissingColumns is true, the set of column names in this and other Dataset can differ; missing columns will be filled with null. Further, the missing columns of this Dataset will be added at the end in the schema of the union result:

val df1 = Seq((1, 2, 3)).toDF("col0", "col1", "col2")
val df2 = Seq((4, 5, 6)).toDF("col1", "col0", "col3")
df1.unionByName(df2, true).show

// output: "col3" is missing at left df1 and added at the end of schema.
// +----+----+----+----+
// |col0|col1|col2|col3|
// +----+----+----+----+
// |   1|   2|   3|NULL|
// |   5|   4|NULL|   6|
// +----+----+----+----+

df2.unionByName(df1, true).show

// output: "col2" is missing at left df2 and added at the end of schema.
// +----+----+----+----+
// |col1|col0|col3|col2|
// +----+----+----+----+
// |   4|   5|   6|NULL|
// |   2|   1|NULL|   3|
// +----+----+----+----+

Note that this supports nested columns in struct and array types. With allowMissingColumns, missing nested columns of struct columns with the same name will also be filled with null values and added to the end of struct. Nested columns in map types are not currently supported.

Mark the Dataset as non-persistent, and remove all blocks for it from memory and disk. This will not un-persist any cached data that is built upon this Dataset.

Mark the Dataset as non-persistent, and remove all blocks for it from memory and disk. This will not un-persist any cached data that is built upon this Dataset.

Unpivot a DataFrame from wide format to long format, optionally leaving identifier columns set. This is the reverse to groupBy(...).pivot(...).agg(...), except for the aggregation, which cannot be reversed.

Unpivot a DataFrame from wide format to long format, optionally leaving identifier columns set. This is the reverse to groupBy(...).pivot(...).agg(...), except for the aggregation, which cannot be reversed.

This function is useful to massage a DataFrame into a format where some columns are identifier columns ("ids"), while all other columns ("values") are "unpivoted" to the rows, leaving just two non-id columns, named as given by variableColumnName and valueColumnName.

val df = Seq((1, 11, 12L), (2, 21, 22L)).toDF("id", "int", "long")
df.show()
// output:
// +---+---+----+
// | id|int|long|
// +---+---+----+
// |  1| 11|  12|
// |  2| 21|  22|
// +---+---+----+

df.unpivot(Array($"id"), Array($"int", $"long"), "variable", "value").show()
// output:
// +---+--------+-----+
// | id|variable|value|
// +---+--------+-----+
// |  1|     int|   11|
// |  1|    long|   12|
// |  2|     int|   21|
// |  2|    long|   22|
// +---+--------+-----+
// schema:
//root
// |-- id: integer (nullable = false)
// |-- variable: string (nullable = false)
// |-- value: long (nullable = true)

When no "id" columns are given, the unpivoted DataFrame consists of only the "variable" and "value" columns.

All "value" columns must share a least common data type. Unless they are the same data type, all "value" columns are cast to the nearest common data type. For instance, types IntegerType and LongType are cast to LongType, while IntegerType and StringType do not have a common data type and unpivot fails with an AnalysisException.

Returns a new Dataset by adding columns or replacing the existing columns that has the same names.

Returns a new Dataset by updating an existing column with metadata.

Defines an event time watermark for this Dataset. A watermark tracks a point in time before which we assume no more late data is going to arrive.

Spark will use this watermark for several purposes:

• To know when a given time window aggregation can be finalized and thus can be emitted when using output modes that do not allow updates.
• To minimize the amount of state that we need to keep for on-going aggregations, mapGroupsWithState and dropDuplicates operators. The current watermark is computed by looking at the MAX(eventTime) seen across all of the partitions in the query minus a user specified delayThreshold. Due to the cost of coordinating this value across partitions, the actual watermark used is only guaranteed to be at least delayThreshold behind the actual event time. In some cases we may still process records that arrive more than delayThreshold late.

Interface for saving the content of the non-streaming Dataset out into external storage.

Create a write configuration builder for v2 sources.

This builder is used to configure and execute write operations. For example, to append to an existing table, run:

df.writeTo("catalog.db.table").append()

This can also be used to create or replace existing tables:

df.writeTo("catalog.db.table").partitionedBy($"col").createOrReplace()

(Scala-specific) Returns a new Dataset where a single column has been expanded to zero or more rows by the provided function. This is similar to a LATERAL VIEW in HiveQL. All columns of the input row are implicitly joined with each value that is output by the function.

Given that this is deprecated, as an alternative, you can explode columns either using functions.explode():

ds.select(explode(split($"words", " ")).as("word"))

or flatMap():

ds.flatMap(_.words.split(" "))

(Scala-specific) Returns a new Dataset where each row has been expanded to zero or more rows by the provided function. This is similar to a LATERAL VIEW in HiveQL. The columns of the input row are implicitly joined with each row that is output by the function.

Given that this is deprecated, as an alternative, you can explode columns either using functions.explode() or flatMap(). The following example uses these alternatives to count the number of books that contain a given word:

case class Book(title: String, words: String)
val ds: DS[Book]

val allWords = ds.select($"title", explode(split($"words", " ")).as("word"))

val bookCountPerWord = allWords.groupBy("word").agg(count_distinct("title"))

Using flatMap() this can similarly be exploded as:

ds.flatMap(_.words.split(" "))

Aggregates on the entire Dataset without groups.

// ds.agg(...) is a shorthand for ds.groupBy().agg(...)
ds.agg(max($"age"), avg($"salary"))
ds.groupBy().agg(max($"age"), avg($"salary"))

(Java-specific) Aggregates on the entire Dataset without groups.

// ds.agg(...) is a shorthand for ds.groupBy().agg(...)
ds.agg(Map("age" -> "max", "salary" -> "avg"))
ds.groupBy().agg(Map("age" -> "max", "salary" -> "avg"))

(Scala-specific) Aggregates on the entire Dataset without groups.

// ds.agg(...) is a shorthand for ds.groupBy().agg(...)
ds.agg(Map("age" -> "max", "salary" -> "avg"))
ds.groupBy().agg(Map("age" -> "max", "salary" -> "avg"))

(Scala-specific) Aggregates on the entire Dataset without groups.

// ds.agg(...) is a shorthand for ds.groupBy().agg(...)
ds.agg("age" -> "max", "salary" -> "avg")
ds.groupBy().agg("age" -> "max", "salary" -> "avg")

(Scala-specific) Returns a new Dataset with an alias set. Same as as.

Returns a new Dataset with an alias set. Same as as.

Selects column based on the column name and returns it as a org.apache.spark.sql.Column.

(Scala-specific) Returns a new Dataset with an alias set.

Returns a checkpointed version of this Dataset. Checkpointing can be used to truncate the logical plan of this Dataset, which is especially useful in iterative algorithms where the plan may grow exponentially. It will be saved to files inside the checkpoint directory set with SparkContext#setCheckpointDir.

Eagerly checkpoint a Dataset and return the new Dataset. Checkpointing can be used to truncate the logical plan of this Dataset, which is especially useful in iterative algorithms where the plan may grow exponentially. It will be saved to files inside the checkpoint directory set with SparkContext#setCheckpointDir.

Returns all column names as an array.

Creates a global temporary view using the given name. The lifetime of this temporary view is tied to this Spark application.

Global temporary view is cross-session. Its lifetime is the lifetime of the Spark application, i.e. it will be automatically dropped when the application terminates. It's tied to a system preserved database global_temp, and we must use the qualified name to refer a global temp view, e.g. SELECT * FROM global_temp.view1.

Creates or replaces a global temporary view using the given name. The lifetime of this temporary view is tied to this Spark application.

Global temporary view is cross-session. Its lifetime is the lifetime of the Spark application, i.e. it will be automatically dropped when the application terminates. It's tied to a system preserved database global_temp, and we must use the qualified name to refer a global temp view, e.g. SELECT * FROM global_temp.view1.

Creates a local temporary view using the given name. The lifetime of this temporary view is tied to the SparkSession that was used to create this Dataset.

Creates a local temporary view using the given name. The lifetime of this temporary view is tied to the SparkSession that was used to create this Dataset.

Local temporary view is session-scoped. Its lifetime is the lifetime of the session that created it, i.e. it will be automatically dropped when the session terminates. It's not tied to any databases, i.e. we can't use db1.view1 to reference a local temporary view.

Create a multi-dimensional cube for the current Dataset using the specified columns, so we can run aggregation on them. See RelationalGroupedDataset for all the available aggregate functions.

This is a variant of cube that can only group by existing columns using column names (i.e. cannot construct expressions).

// Compute the average for all numeric columns cubed by department and group.
ds.cube("department", "group").avg()

// Compute the max age and average salary, cubed by department and gender.
ds.cube($"department", $"gender").agg(Map(
  "salary" -> "avg",
  "age" -> "max"
))

Returns a new Dataset that contains only the unique rows from this Dataset. This is an alias for dropDuplicates.

Note that for a streaming Dataset, this method returns distinct rows only once regardless of the output mode, which the behavior may not be same with DISTINCT in SQL against streaming Dataset.

Returns a new Dataset with column dropped.

This method can only be used to drop top level column. This version of drop accepts a org.apache.spark.sql.Column rather than a name. This is a no-op if the Dataset doesn't have a column with an equivalent expression.

Note: drop(col(colName)) has different semantic with drop(colName), please refer to Dataset#drop(colName: String).

Returns a new Dataset with a column dropped. This is a no-op if schema doesn't contain column name.

This method can only be used to drop top level columns. the colName string is treated literally without further interpretation.

Note: drop(colName) has different semantic with drop(col(colName)), for example: 1, multi column have the same colName:

val df1 = spark.range(0, 2).withColumn("key1", lit(1))
val df2 = spark.range(0, 2).withColumn("key2", lit(2))
val df3 = df1.join(df2)

df3.show
// +---+----+---+----+
// | id|key1| id|key2|
// +---+----+---+----+
// |  0|   1|  0|   2|
// |  0|   1|  1|   2|
// |  1|   1|  0|   2|
// |  1|   1|  1|   2|
// +---+----+---+----+

df3.drop("id").show()
// output: the two 'id' columns are both dropped.
// |key1|key2|
// +----+----+
// |   1|   2|
// |   1|   2|
// |   1|   2|
// |   1|   2|
// +----+----+

df3.drop(col("id")).show()
// ...AnalysisException: [AMBIGUOUS_REFERENCE] Reference `id` is ambiguous...

2, colName contains special characters, like dot.

val df = spark.range(0, 2).withColumn("a.b.c", lit(1))

df.show()
// +---+-----+
// | id|a.b.c|
// +---+-----+
// |  0|    1|
// |  1|    1|
// +---+-----+

df.drop("a.b.c").show()
// +---+
// | id|
// +---+
// |  0|
// |  1|
// +---+

df.drop(col("a.b.c")).show()
// no column match the expression 'a.b.c'
// +---+-----+
// | id|a.b.c|
// +---+-----+
// |  0|    1|
// |  1|    1|
// +---+-----+

Returns a new Dataset with duplicate rows removed, considering only the subset of columns.

For a static batch Dataset, it just drops duplicate rows. For a streaming Dataset, it will keep all data across triggers as intermediate state to drop duplicates rows. You can use withWatermark to limit how late the duplicate data can be and system will accordingly limit the state. In addition, too late data older than watermark will be dropped to avoid any possibility of duplicates.

Returns a new Dataset with duplicate rows removed, considering only the subset of columns.

For a static batch Dataset, it just drops duplicate rows. For a streaming Dataset, it will keep all data across triggers as intermediate state to drop duplicates rows. You can use withWatermark to limit how late the duplicate data can be and system will accordingly limit the state. In addition, too late data older than watermark will be dropped to avoid any possibility of duplicates.

Returns a new Dataset with duplicates rows removed, considering only the subset of columns, within watermark.

This only works with streaming Dataset, and watermark for the input Dataset must be set via withWatermark.

For a streaming Dataset, this will keep all data across triggers as intermediate state to drop duplicated rows. The state will be kept to guarantee the semantic, "Events are deduplicated as long as the time distance of earliest and latest events are smaller than the delay threshold of watermark." Users are encouraged to set the delay threshold of watermark longer than max timestamp differences among duplicated events.

Note: too late data older than watermark will be dropped.

Returns a new Dataset with duplicates rows removed, considering only the subset of columns, within watermark.

This only works with streaming Dataset, and watermark for the input Dataset must be set via withWatermark.

For a streaming Dataset, this will keep all data across triggers as intermediate state to drop duplicated rows. The state will be kept to guarantee the semantic, "Events are deduplicated as long as the time distance of earliest and latest events are smaller than the delay threshold of watermark." Users are encouraged to set the delay threshold of watermark longer than max timestamp differences among duplicated events.

Note: too late data older than watermark will be dropped.

Returns all column names and their data types as an array.

Prints the physical plan to the console for debugging purposes.

Prints the plans (logical and physical) to the console for debugging purposes.

Filters rows using the given SQL expression.

peopleDs.filter("age > 15")

Returns the first row. Alias for head().

(Java-specific) Returns a new Dataset by first applying a function to all elements of this Dataset, and then flattening the results.

(Scala-specific) Returns a new Dataset by first applying a function to all elements of this Dataset, and then flattening the results.

(Java-specific) Runs func on each element of this Dataset.

Applies a function f to all rows.

(Java-specific) Runs func on each partition of this Dataset.

Groups the Dataset using the specified columns, so that we can run aggregation on them. See RelationalGroupedDataset for all the available aggregate functions.

This is a variant of groupBy that can only group by existing columns using column names (i.e. cannot construct expressions).

// Compute the average for all numeric columns grouped by department.
ds.groupBy("department").avg()

// Compute the max age and average salary, grouped by department and gender.
ds.groupBy($"department", $"gender").agg(Map(
  "salary" -> "avg",
  "age" -> "max"
))

Returns the first row.

Inner join with another DataFrame, using the given join expression.

// The following two are equivalent:
df1.join(df2, $"df1Key" === $"df2Key")
df1.join(df2).where($"df1Key" === $"df2Key")

(Java-specific) Equi-join with another DataFrame using the given columns. See the Scala-specific overload for more details.

Equi-join with another DataFrame using the given column. A cross join with a predicate is specified as an inner join. If you would explicitly like to perform a cross join use the crossJoin method.

Different from other join functions, the join column will only appear once in the output, i.e. similar to SQL's JOIN USING syntax.

(Scala-specific) Inner equi-join with another DataFrame using the given columns.

Different from other join functions, the join columns will only appear once in the output, i.e. similar to SQL's JOIN USING syntax.

// Joining df1 and df2 using the columns "user_id" and "user_name"
df1.join(df2, Seq("user_id", "user_name"))

(Java-specific) Inner equi-join with another DataFrame using the given columns. See the Scala-specific overload for more details.

Inner equi-join with another DataFrame using the given column.

Different from other join functions, the join column will only appear once in the output, i.e. similar to SQL's JOIN USING syntax.

// Joining df1 and df2 using the column "user_id"
df1.join(df2, "user_id")

Using inner equi-join to join this Dataset returning a Tuple2 for each pair where condition evaluates to true.

Locally checkpoints a Dataset and return the new Dataset. Checkpointing can be used to truncate the logical plan of this Dataset, which is especially useful in iterative algorithms where the plan may grow exponentially. Local checkpoints are written to executor storage and despite potentially faster they are unreliable and may compromise job completion.

Eagerly locally checkpoints a Dataset and return the new Dataset. Checkpointing can be used to truncate the logical plan of this Dataset, which is especially useful in iterative algorithms where the plan may grow exponentially. Local checkpoints are written to executor storage and despite potentially faster they are unreliable and may compromise job completion.

(Java-specific) Returns a new Dataset that contains the result of applying f to each partition.

Unpivot a DataFrame from wide format to long format, optionally leaving identifier columns set. This is the reverse to groupBy(...).pivot(...).agg(...), except for the aggregation, which cannot be reversed. This is an alias for unpivot.

Unpivot a DataFrame from wide format to long format, optionally leaving identifier columns set. This is the reverse to groupBy(...).pivot(...).agg(...), except for the aggregation, which cannot be reversed. This is an alias for unpivot.

Returns a new Dataset sorted by the given expressions. This is an alias of the sort function.

Returns a new Dataset sorted by the given expressions. This is an alias of the sort function.

Prints the schema up to the given level to the console in a nice tree format.

Prints the schema to the console in a nice tree format.

(Java-specific) Reduces the elements of this Dataset using the specified binary function. The given func must be commutative and associative or the result may be non-deterministic.

Returns a new Dataset partitioned by the given partitioning expressions, using spark.sql.shuffle.partitions as number of partitions. The resulting Dataset is hash partitioned.

This is the same operation as "DISTRIBUTE BY" in SQL (Hive QL).

Returns a new Dataset partitioned by the given partitioning expressions into numPartitions. The resulting Dataset is hash partitioned.

This is the same operation as "DISTRIBUTE BY" in SQL (Hive QL).

Returns a new Dataset partitioned by the given partitioning expressions, using spark.sql.shuffle.partitions as number of partitions. The resulting Dataset is range partitioned.

At least one partition-by expression must be specified. When no explicit sort order is specified, "ascending nulls first" is assumed. Note, the rows are not sorted in each partition of the resulting Dataset.

Note that due to performance reasons this method uses sampling to estimate the ranges. Hence, the output may not be consistent, since sampling can return different values. The sample size can be controlled by the config spark.sql.execution.rangeExchange.sampleSizePerPartition.

Returns a new Dataset partitioned by the given partitioning expressions into numPartitions. The resulting Dataset is range partitioned.

At least one partition-by expression must be specified. When no explicit sort order is specified, "ascending nulls first" is assumed. Note, the rows are not sorted in each partition of the resulting Dataset.

Note that due to performance reasons this method uses sampling to estimate the ranges. Hence, the output may not be consistent, since sampling can return different values. The sample size can be controlled by the config spark.sql.execution.rangeExchange.sampleSizePerPartition.

Create a multi-dimensional rollup for the current Dataset using the specified columns, so we can run aggregation on them. See RelationalGroupedDataset for all the available aggregate functions.

This is a variant of rollup that can only group by existing columns using column names (i.e. cannot construct expressions).

// Compute the average for all numeric columns rolled up by department and group.
ds.rollup("department", "group").avg()

// Compute the max age and average salary, rolled up by department and gender.
ds.rollup($"department", $"gender").agg(Map(
  "salary" -> "avg",
  "age" -> "max"
))

Returns a new Dataset by sampling a fraction of rows, using a random seed.

Returns a new Dataset by sampling a fraction of rows (without replacement), using a random seed.

Returns a new Dataset by sampling a fraction of rows (without replacement), using a user-supplied seed.

Returns a new Dataset by computing the given org.apache.spark.sql.Column expressions for each element.

Returns a new Dataset by computing the given org.apache.spark.sql.Column expressions for each element.

Returns a new Dataset by computing the given org.apache.spark.sql.Column expressions for each element.

Returns a new Dataset by computing the given org.apache.spark.sql.Column expressions for each element.

Selects a set of columns. This is a variant of select that can only select existing columns using column names (i.e. cannot construct expressions).

// The following two are equivalent:
ds.select("colA", "colB")
ds.select($"colA", $"colB")

Selects a set of SQL expressions. This is a variant of select that accepts SQL expressions.

// The following are equivalent:
ds.selectExpr("colA", "colB as newName", "abs(colC)")
ds.select(expr("colA"), expr("colB as newName"), expr("abs(colC)"))

Displays the Dataset in a tabular form. For example:

year  month AVG('Adj Close) MAX('Adj Close)
1980  12    0.503218        0.595103
1981  01    0.523289        0.570307
1982  02    0.436504        0.475256
1983  03    0.410516        0.442194
1984  04    0.450090        0.483521

Displays the top 20 rows of Dataset in a tabular form.

Displays the top 20 rows of Dataset in a tabular form. Strings more than 20 characters will be truncated, and all cells will be aligned right.

Displays the Dataset in a tabular form. Strings more than 20 characters will be truncated, and all cells will be aligned right. For example:

year  month AVG('Adj Close) MAX('Adj Close)
1980  12    0.503218        0.595103
1981  01    0.523289        0.570307
1982  02    0.436504        0.475256
1983  03    0.410516        0.442194
1984  04    0.450090        0.483521

Returns a new Dataset sorted by the given expressions. For example:

ds.sort($"col1", $"col2".desc)

Returns a new Dataset sorted by the specified column, all in ascending order.

// The following 3 are equivalent
ds.sort("sortcol")
ds.sort($"sortcol")
ds.sort($"sortcol".asc)

Returns a new Dataset with each partition sorted by the given expressions.

This is the same operation as "SORT BY" in SQL (Hive QL).

Returns a new Dataset with each partition sorted by the given expressions.

This is the same operation as "SORT BY" in SQL (Hive QL).

Returns the first n rows in the Dataset.

Running take requires moving data into the application's driver process, and doing so with a very large n can crash the driver process with OutOfMemoryError.

Returns the first n rows in the Dataset as a list.

Running take requires moving data into the application's driver process, and doing so with a very large n can crash the driver process with OutOfMemoryError.

Concise syntax for chaining custom transformations.

def featurize(ds: DS[T]): DS[U] = ...

ds
  .transform(featurize)
  .transform(...)

Returns a new Dataset containing union of rows in this Dataset and another Dataset. This is an alias for union.

This is equivalent to UNION ALL in SQL. To do a SQL-style set union (that does deduplication of elements), use this function followed by a distinct.

Also as standard in SQL, this function resolves columns by position (not by name).

Returns a new Dataset containing union of rows in this Dataset and another Dataset.

This is different from both UNION ALL and UNION DISTINCT in SQL. To do a SQL-style set union (that does deduplication of elements), use this function followed by a distinct.

The difference between this function and union is that this function resolves columns by name (not by position):

val df1 = Seq((1, 2, 3)).toDF("col0", "col1", "col2")
val df2 = Seq((4, 5, 6)).toDF("col1", "col2", "col0")
df1.unionByName(df2).show

// output:
// +----+----+----+
// |col0|col1|col2|
// +----+----+----+
// |   1|   2|   3|
// |   6|   4|   5|
// +----+----+----+

Note that this supports nested columns in struct and array types. Nested columns in map types are not currently supported.

Filters rows using the given SQL expression.

peopleDs.where("age > 15")

Filters rows using the given condition. This is an alias for filter.

// The following are equivalent:
peopleDs.filter($"age" > 15)
peopleDs.where($"age" > 15)

Returns a new Dataset by adding a column or replacing the existing column that has the same name.

column's expression must only refer to attributes supplied by this Dataset. It is an error to add a column that refers to some other Dataset.

Returns a new Dataset with a column renamed. This is a no-op if schema doesn't contain existingName.

(Java-specific) Returns a new Dataset by adding columns or replacing the existing columns that has the same names.

colsMap is a map of column name and column, the column must only refer to attribute supplied by this Dataset. It is an error to add columns that refers to some other Dataset.

(Scala-specific) Returns a new Dataset by adding columns or replacing the existing columns that has the same names.

colsMap is a map of column name and column, the column must only refer to attributes supplied by this Dataset. It is an error to add columns that refers to some other Dataset.

(Java-specific) Returns a new Dataset with a columns renamed. This is a no-op if schema doesn't contain existingName.

colsMap is a map of existing column name and new column name.

(Scala-specific) Returns a new Dataset with a columns renamed. This is a no-op if schema doesn't contain existingName.

colsMap is a map of existing column name and new column name.

Registers this Dataset as a temporary table using the given name. The lifetime of this temporary table is tied to the SparkSession that was used to create this Dataset.