Supported Spark Data Sources¶
Parquet¶
When spark.comet.scan.enabled is enabled, Parquet scans will be performed natively by Comet if all data types
in the schema are supported. When this option is not enabled, the scan will fall back to Spark. In this case,
enabling spark.comet.convert.parquet.enabled will immediately convert the data into Arrow format, allowing native
execution to happen after that, but the process may not be efficient.
CSV¶
Comet does not provide native CSV scan, but when spark.comet.convert.csv.enabled is enabled, data is immediately
converted into Arrow format, allowing native execution to happen after that.
JSON¶
Comet does not provide native JSON scan, but when spark.comet.convert.json.enabled is enabled, data is immediately
converted into Arrow format, allowing native execution to happen after that.
Supported Storages¶
Local¶
In progress
HDFS¶
Apache DataFusion Comet native reader seamlessly scans files from remote HDFS for supported formats
Using experimental native DataFusion reader¶
Unlike to native Comet reader the Datafusion reader fully supports nested types processing. This reader is currently experimental only
To build Comet with native DataFusion reader and remote HDFS support it is required to have a JDK installed
Example:
Build a Comet for spark-3.4 provide a JDK path in JAVA_HOME
Provide the JRE linker path in RUSTFLAGS, the path can vary depending on the system. Typically JRE linker is a part of installed JDK
export JAVA_HOME="/opt/homebrew/opt/openjdk@11"
make release PROFILES="-Pspark-3.4" COMET_FEATURES=hdfs RUSTFLAGS="-L $JAVA_HOME/libexec/openjdk.jdk/Contents/Home/lib/server"
Start Comet with experimental reader and HDFS support as described and add additional parameters
--conf spark.comet.scan.impl=native_datafusion \
--conf spark.hadoop.fs.defaultFS="hdfs://namenode:9000" \
--conf spark.hadoop.dfs.client.use.datanode.hostname = true \
--conf dfs.client.use.datanode.hostname = true
Query a struct type from Remote HDFS
spark.read.parquet("hdfs://namenode:9000/user/data").show(false)
root
|-- id: integer (nullable = true)
|-- first_name: string (nullable = true)
|-- personal_info: struct (nullable = true)
| |-- firstName: string (nullable = true)
| |-- lastName: string (nullable = true)
| |-- ageInYears: integer (nullable = true)
25/01/30 16:50:43 INFO core/src/lib.rs: Comet native library version 0.7.0 initialized
== Physical Plan ==
* CometColumnarToRow (2)
+- CometNativeScan: (1)
(1) CometNativeScan:
Output [3]: [id#0, first_name#1, personal_info#4]
Arguments: [id#0, first_name#1, personal_info#4]
(2) CometColumnarToRow [codegen id : 1]
Input [3]: [id#0, first_name#1, personal_info#4]
25/01/30 16:50:44 INFO fs-hdfs-0.1.12/src/hdfs.rs: Connecting to Namenode (hdfs://namenode:9000)
+---+----------+-----------------+
|id |first_name|personal_info |
+---+----------+-----------------+
|2 |Jane |{Jane, Smith, 34}|
|1 |John |{John, Doe, 28} |
+---+----------+-----------------+
Verify the native scan type should be CometNativeScan.
More on HDFS Reader
S3¶
In progress