[jira] [Commented] (SPARK-19477) [SQL] Datasets created from a Dataframe with extra columns retain the extra columns
[
https://issues.apache.org/jira/browse/SPARK-19477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16886192#comment-16886192
]
David Lo commented on SPARK-19477:
--
[~cloud_fan] Could you please elaborate on your suggested workaround?
`ds.map(equality)` isn't compiling for me. Like the original poster, I am
interested in dropping columns that are not defined in a case class when doing
a DataFrame to Dataset[case class] conversion.
> [SQL] Datasets created from a Dataframe with extra columns retain the extra
> columns
> ---
>
> Key: SPARK-19477
> URL: https://issues.apache.org/jira/browse/SPARK-19477
> Project: Spark
> Issue Type: Bug
> Components: SQL
>Affects Versions: 2.1.0
>Reporter: Don Drake
>Priority: Major
> Labels: bulk-closed
>
> In 1.6, when you created a Dataset from a Dataframe that had extra columns,
> the columns not in the case class were dropped from the Dataset.
> For example in 1.6, the column c4 is gone:
> {code}
> scala> case class F(f1: String, f2: String, f3:String)
> defined class F
> scala> import sqlContext.implicits._
> import sqlContext.implicits._
> scala> val df = Seq(("a","b","c","x"), ("d", "e", "f","y"), ("h", "i",
> "j","z")).toDF("f1", "f2", "f3", "c4")
> df: org.apache.spark.sql.DataFrame = [f1: string, f2: string, f3: string, c4:
> string]
> scala> val ds = df.as[F]
> ds: org.apache.spark.sql.Dataset[F] = [f1: string, f2: string, f3: string]
> scala> ds.show
> +---+---+---+
> | f1| f2| f3|
> +---+---+---+
> | a| b| c|
> | d| e| f|
> | h| i| j|
> {code}
> This seems to have changed in Spark 2.0 and also 2.1:
> Spark 2.1.0:
> {code}
> scala> case class F(f1: String, f2: String, f3:String)
> defined class F
> scala> import spark.implicits._
> import spark.implicits._
> scala> val df = Seq(("a","b","c","x"), ("d", "e", "f","y"), ("h", "i",
> "j","z")).toDF("f1", "f2", "f3", "c4")
> df: org.apache.spark.sql.DataFrame = [f1: string, f2: string ... 2 more
> fields]
> scala> val ds = df.as[F]
> ds: org.apache.spark.sql.Dataset[F] = [f1: string, f2: string ... 2 more
> fields]
> scala> ds.show
> +---+---+---+---+
> | f1| f2| f3| c4|
> +---+---+---+---+
> | a| b| c| x|
> | d| e| f| y|
> | h| i| j| z|
> +---+---+---+---+
> scala> import org.apache.spark.sql.Encoders
> import org.apache.spark.sql.Encoders
> scala> val fEncoder = Encoders.product[F]
> fEncoder: org.apache.spark.sql.Encoder[F] = class[f1[0]: string, f2[0]:
> string, f3[0]: string]
> scala> fEncoder.schema == ds.schema
> res2: Boolean = false
> scala> ds.schema
> res3: org.apache.spark.sql.types.StructType =
> StructType(StructField(f1,StringType,true), StructField(f2,StringType,true),
> StructField(f3,StringType,true), StructField(c4,StringType,true))
> scala> fEncoder.schema
> res4: org.apache.spark.sql.types.StructType =
> StructType(StructField(f1,StringType,true), StructField(f2,StringType,true),
> StructField(f3,StringType,true))
> {code}
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[jira] [Commented] (SPARK-19477) [SQL] Datasets created from a Dataframe with extra columns retain the extra columns
[
https://issues.apache.org/jira/browse/SPARK-19477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=15862562#comment-15862562
]
Wenchen Fan commented on SPARK-19477:
-
a simple workaround will be `ds.map(equality)`.
> [SQL] Datasets created from a Dataframe with extra columns retain the extra
> columns
> ---
>
> Key: SPARK-19477
> URL: https://issues.apache.org/jira/browse/SPARK-19477
> Project: Spark
> Issue Type: Bug
> Components: SQL
>Affects Versions: 2.1.0
>Reporter: Don Drake
>
> In 1.6, when you created a Dataset from a Dataframe that had extra columns,
> the columns not in the case class were dropped from the Dataset.
> For example in 1.6, the column c4 is gone:
> {code}
> scala> case class F(f1: String, f2: String, f3:String)
> defined class F
> scala> import sqlContext.implicits._
> import sqlContext.implicits._
> scala> val df = Seq(("a","b","c","x"), ("d", "e", "f","y"), ("h", "i",
> "j","z")).toDF("f1", "f2", "f3", "c4")
> df: org.apache.spark.sql.DataFrame = [f1: string, f2: string, f3: string, c4:
> string]
> scala> val ds = df.as[F]
> ds: org.apache.spark.sql.Dataset[F] = [f1: string, f2: string, f3: string]
> scala> ds.show
> +---+---+---+
> | f1| f2| f3|
> +---+---+---+
> | a| b| c|
> | d| e| f|
> | h| i| j|
> {code}
> This seems to have changed in Spark 2.0 and also 2.1:
> Spark 2.1.0:
> {code}
> scala> case class F(f1: String, f2: String, f3:String)
> defined class F
> scala> import spark.implicits._
> import spark.implicits._
> scala> val df = Seq(("a","b","c","x"), ("d", "e", "f","y"), ("h", "i",
> "j","z")).toDF("f1", "f2", "f3", "c4")
> df: org.apache.spark.sql.DataFrame = [f1: string, f2: string ... 2 more
> fields]
> scala> val ds = df.as[F]
> ds: org.apache.spark.sql.Dataset[F] = [f1: string, f2: string ... 2 more
> fields]
> scala> ds.show
> +---+---+---+---+
> | f1| f2| f3| c4|
> +---+---+---+---+
> | a| b| c| x|
> | d| e| f| y|
> | h| i| j| z|
> +---+---+---+---+
> scala> import org.apache.spark.sql.Encoders
> import org.apache.spark.sql.Encoders
> scala> val fEncoder = Encoders.product[F]
> fEncoder: org.apache.spark.sql.Encoder[F] = class[f1[0]: string, f2[0]:
> string, f3[0]: string]
> scala> fEncoder.schema == ds.schema
> res2: Boolean = false
> scala> ds.schema
> res3: org.apache.spark.sql.types.StructType =
> StructType(StructField(f1,StringType,true), StructField(f2,StringType,true),
> StructField(f3,StringType,true), StructField(c4,StringType,true))
> scala> fEncoder.schema
> res4: org.apache.spark.sql.types.StructType =
> StructType(StructField(f1,StringType,true), StructField(f2,StringType,true),
> StructField(f3,StringType,true))
> {code}
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[jira] [Commented] (SPARK-19477) [SQL] Datasets created from a Dataframe with extra columns retain the extra columns
[
https://issues.apache.org/jira/browse/SPARK-19477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=15862560#comment-15862560
]
Don Drake commented on SPARK-19477:
---
How does lazy apply here? If I read/create a dataframe with extra columns, then
do ds = df.as[XYZ], then immediately ds.write.parquet("file"), the write
trigger should enable any lazy functionality if I understand this.
Do you have a suggested workaround? I'm currently retrieving the encoder for
the case class to get the schema, then calling ds.select() on the columns from
the schema.
> [SQL] Datasets created from a Dataframe with extra columns retain the extra
> columns
> ---
>
> Key: SPARK-19477
> URL: https://issues.apache.org/jira/browse/SPARK-19477
> Project: Spark
> Issue Type: Bug
> Components: SQL
>Affects Versions: 2.1.0
>Reporter: Don Drake
>
> In 1.6, when you created a Dataset from a Dataframe that had extra columns,
> the columns not in the case class were dropped from the Dataset.
> For example in 1.6, the column c4 is gone:
> {code}
> scala> case class F(f1: String, f2: String, f3:String)
> defined class F
> scala> import sqlContext.implicits._
> import sqlContext.implicits._
> scala> val df = Seq(("a","b","c","x"), ("d", "e", "f","y"), ("h", "i",
> "j","z")).toDF("f1", "f2", "f3", "c4")
> df: org.apache.spark.sql.DataFrame = [f1: string, f2: string, f3: string, c4:
> string]
> scala> val ds = df.as[F]
> ds: org.apache.spark.sql.Dataset[F] = [f1: string, f2: string, f3: string]
> scala> ds.show
> +---+---+---+
> | f1| f2| f3|
> +---+---+---+
> | a| b| c|
> | d| e| f|
> | h| i| j|
> {code}
> This seems to have changed in Spark 2.0 and also 2.1:
> Spark 2.1.0:
> {code}
> scala> case class F(f1: String, f2: String, f3:String)
> defined class F
> scala> import spark.implicits._
> import spark.implicits._
> scala> val df = Seq(("a","b","c","x"), ("d", "e", "f","y"), ("h", "i",
> "j","z")).toDF("f1", "f2", "f3", "c4")
> df: org.apache.spark.sql.DataFrame = [f1: string, f2: string ... 2 more
> fields]
> scala> val ds = df.as[F]
> ds: org.apache.spark.sql.Dataset[F] = [f1: string, f2: string ... 2 more
> fields]
> scala> ds.show
> +---+---+---+---+
> | f1| f2| f3| c4|
> +---+---+---+---+
> | a| b| c| x|
> | d| e| f| y|
> | h| i| j| z|
> +---+---+---+---+
> scala> import org.apache.spark.sql.Encoders
> import org.apache.spark.sql.Encoders
> scala> val fEncoder = Encoders.product[F]
> fEncoder: org.apache.spark.sql.Encoder[F] = class[f1[0]: string, f2[0]:
> string, f3[0]: string]
> scala> fEncoder.schema == ds.schema
> res2: Boolean = false
> scala> ds.schema
> res3: org.apache.spark.sql.types.StructType =
> StructType(StructField(f1,StringType,true), StructField(f2,StringType,true),
> StructField(f3,StringType,true), StructField(c4,StringType,true))
> scala> fEncoder.schema
> res4: org.apache.spark.sql.types.StructType =
> StructType(StructField(f1,StringType,true), StructField(f2,StringType,true),
> StructField(f3,StringType,true))
> {code}
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[jira] [Commented] (SPARK-19477) [SQL] Datasets created from a Dataframe with extra columns retain the extra columns
[
https://issues.apache.org/jira/browse/SPARK-19477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=15861918#comment-15861918
]
Michael Armbrust commented on SPARK-19477:
--
If a lot of people are confused by this being lazy we can change it (didn't we
already change it in 1.6 -> 2.0 in the other direction?). It would have to be
configurable though, since removing columns could be a breaking change.
> [SQL] Datasets created from a Dataframe with extra columns retain the extra
> columns
> ---
>
> Key: SPARK-19477
> URL: https://issues.apache.org/jira/browse/SPARK-19477
> Project: Spark
> Issue Type: Bug
> Components: SQL
>Affects Versions: 2.1.0
>Reporter: Don Drake
>
> In 1.6, when you created a Dataset from a Dataframe that had extra columns,
> the columns not in the case class were dropped from the Dataset.
> For example in 1.6, the column c4 is gone:
> {code}
> scala> case class F(f1: String, f2: String, f3:String)
> defined class F
> scala> import sqlContext.implicits._
> import sqlContext.implicits._
> scala> val df = Seq(("a","b","c","x"), ("d", "e", "f","y"), ("h", "i",
> "j","z")).toDF("f1", "f2", "f3", "c4")
> df: org.apache.spark.sql.DataFrame = [f1: string, f2: string, f3: string, c4:
> string]
> scala> val ds = df.as[F]
> ds: org.apache.spark.sql.Dataset[F] = [f1: string, f2: string, f3: string]
> scala> ds.show
> +---+---+---+
> | f1| f2| f3|
> +---+---+---+
> | a| b| c|
> | d| e| f|
> | h| i| j|
> {code}
> This seems to have changed in Spark 2.0 and also 2.1:
> Spark 2.1.0:
> {code}
> scala> case class F(f1: String, f2: String, f3:String)
> defined class F
> scala> import spark.implicits._
> import spark.implicits._
> scala> val df = Seq(("a","b","c","x"), ("d", "e", "f","y"), ("h", "i",
> "j","z")).toDF("f1", "f2", "f3", "c4")
> df: org.apache.spark.sql.DataFrame = [f1: string, f2: string ... 2 more
> fields]
> scala> val ds = df.as[F]
> ds: org.apache.spark.sql.Dataset[F] = [f1: string, f2: string ... 2 more
> fields]
> scala> ds.show
> +---+---+---+---+
> | f1| f2| f3| c4|
> +---+---+---+---+
> | a| b| c| x|
> | d| e| f| y|
> | h| i| j| z|
> +---+---+---+---+
> scala> import org.apache.spark.sql.Encoders
> import org.apache.spark.sql.Encoders
> scala> val fEncoder = Encoders.product[F]
> fEncoder: org.apache.spark.sql.Encoder[F] = class[f1[0]: string, f2[0]:
> string, f3[0]: string]
> scala> fEncoder.schema == ds.schema
> res2: Boolean = false
> scala> ds.schema
> res3: org.apache.spark.sql.types.StructType =
> StructType(StructField(f1,StringType,true), StructField(f2,StringType,true),
> StructField(f3,StringType,true), StructField(c4,StringType,true))
> scala> fEncoder.schema
> res4: org.apache.spark.sql.types.StructType =
> StructType(StructField(f1,StringType,true), StructField(f2,StringType,true),
> StructField(f3,StringType,true))
> {code}
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[jira] [Commented] (SPARK-19477) [SQL] Datasets created from a Dataframe with extra columns retain the extra columns
[
https://issues.apache.org/jira/browse/SPARK-19477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=15859795#comment-15859795
]
Christophe Préaud commented on SPARK-19477:
---
As a workaround, mapping the dataset with *identity* fix the issue:
```scala
scala> ds.show
+---+---+---+---+
| f1| f2| f3| c4|
+---+---+---+---+
| a| b| c| x|
| d| e| f| y|
| h| i| j| z|
+---+---+---+---+
scala> ds.map(identity).show
+---+---+---+
| f1| f2| f3|
+---+---+---+
| a| b| c|
| d| e| f|
| h| i| j|
+---+---+---+
```
> [SQL] Datasets created from a Dataframe with extra columns retain the extra
> columns
> ---
>
> Key: SPARK-19477
> URL: https://issues.apache.org/jira/browse/SPARK-19477
> Project: Spark
> Issue Type: Bug
> Components: SQL
>Affects Versions: 2.1.0
>Reporter: Don Drake
>
> In 1.6, when you created a Dataset from a Dataframe that had extra columns,
> the columns not in the case class were dropped from the Dataset.
> For example in 1.6, the column c4 is gone:
> {code}
> scala> case class F(f1: String, f2: String, f3:String)
> defined class F
> scala> import sqlContext.implicits._
> import sqlContext.implicits._
> scala> val df = Seq(("a","b","c","x"), ("d", "e", "f","y"), ("h", "i",
> "j","z")).toDF("f1", "f2", "f3", "c4")
> df: org.apache.spark.sql.DataFrame = [f1: string, f2: string, f3: string, c4:
> string]
> scala> val ds = df.as[F]
> ds: org.apache.spark.sql.Dataset[F] = [f1: string, f2: string, f3: string]
> scala> ds.show
> +---+---+---+
> | f1| f2| f3|
> +---+---+---+
> | a| b| c|
> | d| e| f|
> | h| i| j|
> {code}
> This seems to have changed in Spark 2.0 and also 2.1:
> Spark 2.1.0:
> {code}
> scala> case class F(f1: String, f2: String, f3:String)
> defined class F
> scala> import spark.implicits._
> import spark.implicits._
> scala> val df = Seq(("a","b","c","x"), ("d", "e", "f","y"), ("h", "i",
> "j","z")).toDF("f1", "f2", "f3", "c4")
> df: org.apache.spark.sql.DataFrame = [f1: string, f2: string ... 2 more
> fields]
> scala> val ds = df.as[F]
> ds: org.apache.spark.sql.Dataset[F] = [f1: string, f2: string ... 2 more
> fields]
> scala> ds.show
> +---+---+---+---+
> | f1| f2| f3| c4|
> +---+---+---+---+
> | a| b| c| x|
> | d| e| f| y|
> | h| i| j| z|
> +---+---+---+---+
> scala> import org.apache.spark.sql.Encoders
> import org.apache.spark.sql.Encoders
> scala> val fEncoder = Encoders.product[F]
> fEncoder: org.apache.spark.sql.Encoder[F] = class[f1[0]: string, f2[0]:
> string, f3[0]: string]
> scala> fEncoder.schema == ds.schema
> res2: Boolean = false
> scala> ds.schema
> res3: org.apache.spark.sql.types.StructType =
> StructType(StructField(f1,StringType,true), StructField(f2,StringType,true),
> StructField(f3,StringType,true), StructField(c4,StringType,true))
> scala> fEncoder.schema
> res4: org.apache.spark.sql.types.StructType =
> StructType(StructField(f1,StringType,true), StructField(f2,StringType,true),
> StructField(f3,StringType,true))
> {code}
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[jira] [Commented] (SPARK-19477) [SQL] Datasets created from a Dataframe with extra columns retain the extra columns
[
https://issues.apache.org/jira/browse/SPARK-19477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=15856329#comment-15856329
]
Wenchen Fan commented on SPARK-19477:
-
I think the most confusing part maybe the fact that `Dataset.as[T]` is lazy.
In your example, there is a `df` with 4 columns, and when you call `df.as[F]`,
it still has 4 columns. But when you do `df.as[F].map(x => x)`, it has 3
columns.
Maybe it's more intuitive to make `Dataset.as[T]` eagerly change the underlying
plan to adjust columns? cc [~marmbrus] [~lian cheng]
> [SQL] Datasets created from a Dataframe with extra columns retain the extra
> columns
> ---
>
> Key: SPARK-19477
> URL: https://issues.apache.org/jira/browse/SPARK-19477
> Project: Spark
> Issue Type: Bug
> Components: SQL
>Affects Versions: 2.1.0
>Reporter: Don Drake
>
> In 1.6, when you created a Dataset from a Dataframe that had extra columns,
> the columns not in the case class were dropped from the Dataset.
> For example in 1.6, the column c4 is gone:
> {code}
> scala> case class F(f1: String, f2: String, f3:String)
> defined class F
> scala> import sqlContext.implicits._
> import sqlContext.implicits._
> scala> val df = Seq(("a","b","c","x"), ("d", "e", "f","y"), ("h", "i",
> "j","z")).toDF("f1", "f2", "f3", "c4")
> df: org.apache.spark.sql.DataFrame = [f1: string, f2: string, f3: string, c4:
> string]
> scala> val ds = df.as[F]
> ds: org.apache.spark.sql.Dataset[F] = [f1: string, f2: string, f3: string]
> scala> ds.show
> +---+---+---+
> | f1| f2| f3|
> +---+---+---+
> | a| b| c|
> | d| e| f|
> | h| i| j|
> {code}
> This seems to have changed in Spark 2.0 and also 2.1:
> Spark 2.1.0:
> {code}
> scala> case class F(f1: String, f2: String, f3:String)
> defined class F
> scala> import spark.implicits._
> import spark.implicits._
> scala> val df = Seq(("a","b","c","x"), ("d", "e", "f","y"), ("h", "i",
> "j","z")).toDF("f1", "f2", "f3", "c4")
> df: org.apache.spark.sql.DataFrame = [f1: string, f2: string ... 2 more
> fields]
> scala> val ds = df.as[F]
> ds: org.apache.spark.sql.Dataset[F] = [f1: string, f2: string ... 2 more
> fields]
> scala> ds.show
> +---+---+---+---+
> | f1| f2| f3| c4|
> +---+---+---+---+
> | a| b| c| x|
> | d| e| f| y|
> | h| i| j| z|
> +---+---+---+---+
> scala> import org.apache.spark.sql.Encoders
> import org.apache.spark.sql.Encoders
> scala> val fEncoder = Encoders.product[F]
> fEncoder: org.apache.spark.sql.Encoder[F] = class[f1[0]: string, f2[0]:
> string, f3[0]: string]
> scala> fEncoder.schema == ds.schema
> res2: Boolean = false
> scala> ds.schema
> res3: org.apache.spark.sql.types.StructType =
> StructType(StructField(f1,StringType,true), StructField(f2,StringType,true),
> StructField(f3,StringType,true), StructField(c4,StringType,true))
> scala> fEncoder.schema
> res4: org.apache.spark.sql.types.StructType =
> StructType(StructField(f1,StringType,true), StructField(f2,StringType,true),
> StructField(f3,StringType,true))
> {code}
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[jira] [Commented] (SPARK-19477) [SQL] Datasets created from a Dataframe with extra columns retain the extra columns
[
https://issues.apache.org/jira/browse/SPARK-19477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=15855677#comment-15855677
]
Song Jun commented on SPARK-19477:
--
thanks， I got it~
> [SQL] Datasets created from a Dataframe with extra columns retain the extra
> columns
> ---
>
> Key: SPARK-19477
> URL: https://issues.apache.org/jira/browse/SPARK-19477
> Project: Spark
> Issue Type: Bug
> Components: SQL
>Affects Versions: 2.1.0
>Reporter: Don Drake
>
> In 1.6, when you created a Dataset from a Dataframe that had extra columns,
> the columns not in the case class were dropped from the Dataset.
> For example in 1.6, the column c4 is gone:
> {code}
> scala> case class F(f1: String, f2: String, f3:String)
> defined class F
> scala> import sqlContext.implicits._
> import sqlContext.implicits._
> scala> val df = Seq(("a","b","c","x"), ("d", "e", "f","y"), ("h", "i",
> "j","z")).toDF("f1", "f2", "f3", "c4")
> df: org.apache.spark.sql.DataFrame = [f1: string, f2: string, f3: string, c4:
> string]
> scala> val ds = df.as[F]
> ds: org.apache.spark.sql.Dataset[F] = [f1: string, f2: string, f3: string]
> scala> ds.show
> +---+---+---+
> | f1| f2| f3|
> +---+---+---+
> | a| b| c|
> | d| e| f|
> | h| i| j|
> {code}
> This seems to have changed in Spark 2.0 and also 2.1:
> Spark 2.1.0:
> {code}
> scala> case class F(f1: String, f2: String, f3:String)
> defined class F
> scala> import spark.implicits._
> import spark.implicits._
> scala> val df = Seq(("a","b","c","x"), ("d", "e", "f","y"), ("h", "i",
> "j","z")).toDF("f1", "f2", "f3", "c4")
> df: org.apache.spark.sql.DataFrame = [f1: string, f2: string ... 2 more
> fields]
> scala> val ds = df.as[F]
> ds: org.apache.spark.sql.Dataset[F] = [f1: string, f2: string ... 2 more
> fields]
> scala> ds.show
> +---+---+---+---+
> | f1| f2| f3| c4|
> +---+---+---+---+
> | a| b| c| x|
> | d| e| f| y|
> | h| i| j| z|
> +---+---+---+---+
> scala> import org.apache.spark.sql.Encoders
> import org.apache.spark.sql.Encoders
> scala> val fEncoder = Encoders.product[F]
> fEncoder: org.apache.spark.sql.Encoder[F] = class[f1[0]: string, f2[0]:
> string, f3[0]: string]
> scala> fEncoder.schema == ds.schema
> res2: Boolean = false
> scala> ds.schema
> res3: org.apache.spark.sql.types.StructType =
> StructType(StructField(f1,StringType,true), StructField(f2,StringType,true),
> StructField(f3,StringType,true), StructField(c4,StringType,true))
> scala> fEncoder.schema
> res4: org.apache.spark.sql.types.StructType =
> StructType(StructField(f1,StringType,true), StructField(f2,StringType,true),
> StructField(f3,StringType,true))
> {code}
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[jira] [Commented] (SPARK-19477) [SQL] Datasets created from a Dataframe with extra columns retain the extra columns
[
https://issues.apache.org/jira/browse/SPARK-19477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=1582#comment-1582
]
Wenchen Fan commented on SPARK-19477:
-
The type T of Dataset and the schema of Dataset should be treated differently,
as you can apply both relational operations(select, where, ...) and typed
operations (map, filter, ...).
When you call `show`, it prints data in columnar format, so it's more like a
relational operation and should respect the schema instead of type T/encoder.
> [SQL] Datasets created from a Dataframe with extra columns retain the extra
> columns
> ---
>
> Key: SPARK-19477
> URL: https://issues.apache.org/jira/browse/SPARK-19477
> Project: Spark
> Issue Type: Bug
> Components: SQL
>Affects Versions: 2.1.0
>Reporter: Don Drake
>
> In 1.6, when you created a Dataset from a Dataframe that had extra columns,
> the columns not in the case class were dropped from the Dataset.
> For example in 1.6, the column c4 is gone:
> {code}
> scala> case class F(f1: String, f2: String, f3:String)
> defined class F
> scala> import sqlContext.implicits._
> import sqlContext.implicits._
> scala> val df = Seq(("a","b","c","x"), ("d", "e", "f","y"), ("h", "i",
> "j","z")).toDF("f1", "f2", "f3", "c4")
> df: org.apache.spark.sql.DataFrame = [f1: string, f2: string, f3: string, c4:
> string]
> scala> val ds = df.as[F]
> ds: org.apache.spark.sql.Dataset[F] = [f1: string, f2: string, f3: string]
> scala> ds.show
> +---+---+---+
> | f1| f2| f3|
> +---+---+---+
> | a| b| c|
> | d| e| f|
> | h| i| j|
> {code}
> This seems to have changed in Spark 2.0 and also 2.1:
> Spark 2.1.0:
> {code}
> scala> case class F(f1: String, f2: String, f3:String)
> defined class F
> scala> import spark.implicits._
> import spark.implicits._
> scala> val df = Seq(("a","b","c","x"), ("d", "e", "f","y"), ("h", "i",
> "j","z")).toDF("f1", "f2", "f3", "c4")
> df: org.apache.spark.sql.DataFrame = [f1: string, f2: string ... 2 more
> fields]
> scala> val ds = df.as[F]
> ds: org.apache.spark.sql.Dataset[F] = [f1: string, f2: string ... 2 more
> fields]
> scala> ds.show
> +---+---+---+---+
> | f1| f2| f3| c4|
> +---+---+---+---+
> | a| b| c| x|
> | d| e| f| y|
> | h| i| j| z|
> +---+---+---+---+
> scala> import org.apache.spark.sql.Encoders
> import org.apache.spark.sql.Encoders
> scala> val fEncoder = Encoders.product[F]
> fEncoder: org.apache.spark.sql.Encoder[F] = class[f1[0]: string, f2[0]:
> string, f3[0]: string]
> scala> fEncoder.schema == ds.schema
> res2: Boolean = false
> scala> ds.schema
> res3: org.apache.spark.sql.types.StructType =
> StructType(StructField(f1,StringType,true), StructField(f2,StringType,true),
> StructField(f3,StringType,true), StructField(c4,StringType,true))
> scala> fEncoder.schema
> res4: org.apache.spark.sql.types.StructType =
> StructType(StructField(f1,StringType,true), StructField(f2,StringType,true),
> StructField(f3,StringType,true))
> {code}
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