如何在 Spark 2.4.4 中使用增量創建表？

Question

這是 Spark 2.4.4 和 Delta Lake 0.5.0。

我正在嘗試使用 delta 數據源創建一個表，但似乎我遺漏了一些東西。 盡管CREATE TABLE USING delta命令工作正常，但表目錄沒有被創建， insertInto也沒有工作。

以下CREATE TABLE USING delta工作正常，但insertInto失敗。

scala> sql("""
create table t5
USING delta
LOCATION '/tmp/delta'
""").show

scala> spark.catalog.listTables.where('name === "t5").show
+----+--------+-----------+---------+-----------+
|name|database|description|tableType|isTemporary|
+----+--------+-----------+---------+-----------+
|  t5| default|       null| EXTERNAL|      false|
+----+--------+-----------+---------+-----------+

scala> spark.range(5).write.option("mergeSchema", true).insertInto("t5")
org.apache.spark.sql.AnalysisException: `default`.`t5` requires that the data to be inserted have the same number of columns as the target table: target table has 0 column(s) but the inserted data has 1 column(s), including 0 partition column(s) having constant value(s).;
  at org.apache.spark.sql.execution.datasources.PreprocessTableInsertion.org$apache$spark$sql$execution$datasources$PreprocessTableInsertion$$preprocess(rules.scala:341)
  ...

我以為我會用定義的列創建，但這也不起作用。

scala> sql("""
create table t6
(id LONG, name STRING)
USING delta
LOCATION '/tmp/delta'
""").show
org.apache.spark.sql.AnalysisException: delta does not allow user-specified schemas.;
  at org.apache.spark.sql.execution.datasources.DataSource.resolveRelation(DataSource.scala:325)
  at org.apache.spark.sql.execution.command.CreateDataSourceTableCommand.run(createDataSourceTables.scala:78)
  at org.apache.spark.sql.execution.command.ExecutedCommandExec.sideEffectResult$lzycompute(commands.scala:70)
  at org.apache.spark.sql.execution.command.ExecutedCommandExec.sideEffectResult(commands.scala:68)
  at org.apache.spark.sql.execution.command.ExecutedCommandExec.executeCollect(commands.scala:79)
  at org.apache.spark.sql.Dataset.$anonfun$logicalPlan$1(Dataset.scala:194)
  at org.apache.spark.sql.Dataset.$anonfun$withAction$2(Dataset.scala:3370)
  at org.apache.spark.sql.execution.SQLExecution$.$anonfun$withNewExecutionId$1(SQLExecution.scala:78)
  at org.apache.spark.sql.execution.SQLExecution$.withSQLConfPropagated(SQLExecution.scala:125)
  at org.apache.spark.sql.execution.SQLExecution$.withNewExecutionId(SQLExecution.scala:73)
  at org.apache.spark.sql.Dataset.withAction(Dataset.scala:3370)
  at org.apache.spark.sql.Dataset.<init>(Dataset.scala:194)
  at org.apache.spark.sql.Dataset$.ofRows(Dataset.scala:79)
  at org.apache.spark.sql.SparkSession.sql(SparkSession.scala:642)
  ... 54 elided

Answer 1

Delta 的 OSS 版本目前還沒有 SQL Create Table 語法。 這將在未來的版本中使用 Spark 3.0 實現。

要創建 Delta 表，您必須以 Delta 格式寫出一個 DataFrame。 Python中的一個例子是

df.write.format("delta").save("/some/data/path")

這是 Python、Scala 和 Java 的創建表文檔的鏈接。

Answer 2

tl; dr CREATE TABLE USING delta在 3.0.0 之前的 Spark 和 0.7.0 之前的 Delta Lake 不支持。

---

Delta Lake 0.7.0 和 Spark 3.0.0（都剛剛發布）支持CREATE TABLE SQL 命令。

請務必使用spark.sql.catalog.spark_catalog配置屬性和org.apache.spark.sql.delta.catalog.DeltaCatalog來“安裝”Delta SQL。

$ ./bin/spark-submit \
  --packages io.delta:delta-core_2.12:0.7.0 \
  --conf spark.sql.extensions=io.delta.sql.DeltaSparkSessionExtension \
  --conf spark.sql.catalog.spark_catalog=org.apache.spark.sql.delta.catalog.DeltaCatalog

scala> spark.version
res0: String = 3.0.0

scala> sql("CREATE TABLE delta_101 (id LONG) USING delta").show
++
||
++
++

scala> spark.table("delta_101").show
+---+
| id|
+---+
+---+

scala> sql("DESCRIBE EXTENDED delta_101").show(truncate = false)
+----------------------------+---------------------------------------------------------+-------+
|col_name                    |data_type                                                |comment|
+----------------------------+---------------------------------------------------------+-------+
|id                          |bigint                                                   |       |
|                            |                                                         |       |
|# Partitioning              |                                                         |       |
|Not partitioned             |                                                         |       |
|                            |                                                         |       |
|# Detailed Table Information|                                                         |       |
|Name                        |default.delta_101                                        |       |
|Location                    |file:/Users/jacek/dev/oss/spark/spark-warehouse/delta_101|       |
|Provider                    |delta                                                    |       |
|Table Properties            |[]                                                       |       |
+----------------------------+---------------------------------------------------------+-------+

Answer 3

pyspark 3.0.0 & delta 0.7.0 的示例

print(f"LOCATION '{location}")
spark.sql(f"""
CREATE OR REPLACE TABLE  {TABLE_NAME} (
  CD_DEVICE INT, 
  FC_LOCAL_TIME TIMESTAMP,  
  CD_TYPE_DEVICE STRING,
  CONSUMTION DOUBLE,
  YEAR INT,
  MONTH INT, 
  DAY INT )
USING DELTA
PARTITIONED BY (YEAR , MONTH , DAY, FC_LOCAL_TIME)
LOCATION '{location}'
""")

其中“位置”是火花集群模式保存增量表的目錄 HDFS。