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https://issues.apache.org/jira/browse/SPARK-21074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16769866#comment-16769866
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t oo commented on SPARK-21074:
------------------------------
@[~spektom] gentle ping
> Parquet files are read fully even though only count() is requested
> ------------------------------------------------------------------
>
> Key: SPARK-21074
> URL: https://issues.apache.org/jira/browse/SPARK-21074
> Project: Spark
> Issue Type: Improvement
> Components: Optimizer
> Affects Versions: 2.1.0
> Reporter: Michael Spector
> Priority: Major
>
> I have the following sample code that creates parquet files:
> {code:java}
> val spark = SparkSession.builder()
> .config("spark.hadoop.mapreduce.fileoutputcommitter.algorithm.version",
> "2")
> .config("spark.hadoop.parquet.metadata.read.parallelism", "50")
> .appName("Test Write").getOrCreate()
> val sqc = spark.sqlContext
> import sqc.implicits._
> val random = new scala.util.Random(31L)
> (1465720077 to 1465720077+10000000).map(x => Event(x, random.nextString(2)))
> .toDS()
> .write
> .mode(SaveMode.Overwrite)
> .parquet("s3://my-bucket/test")
> {code}
> Afterwards, I'm trying to read these files with the following code:
> {code:java}
> val spark = SparkSession.builder()
> .config("spark.hadoop.mapreduce.fileoutputcommitter.algorithm.version",
> "2")
> .config("spark.hadoop.parquet.metadata.read.parallelism", "50")
> .config("spark.sql.parquet.filterPushdown", "true")
> .appName("Test Read").getOrCreate()
> spark.sqlContext.read
> .option("mergeSchema", "false")
> .parquet("s3://my-bucket/test")
> .count()
> {code}
> I've enabled DEBUG log level to see what requests are actually sent through
> S3 API, and I've figured out that in addition to parquet "footer" retrieval
> there are requests that ask for whole file content.
> For example, this is full content request example:
> {noformat}
> 17/06/13 05:46:50 DEBUG wire: http-outgoing-1 >> "GET
> /test/part-00000-b8a8a1b7-0581-401f-b520-27fa9600f35e.snappy.parquet
> HTTP/1.1[\r][\n]"
> ....
> 17/06/13 05:46:50 DEBUG wire: http-outgoing-1 << "Content-Range: bytes
> 0-7472093/7472094[\r][\n]"
> ....
> 17/06/13 05:46:50 DEBUG wire: http-outgoing-1 << "Content-Length:
> 7472094[\r][\n]"
> {noformat}
> And this is partial request example for footer only:
> {noformat}
> 17/06/13 05:46:50 DEBUG headers: http-outgoing-2 >> GET
> /test/part-00000-b8a8a1b7-0581-401f-b520-27fa9600f35e.snappy.parquet HTTP/1.1
> ....
> 17/06/13 05:46:50 DEBUG headers: http-outgoing-2 >> Range:
> bytes=7472086-7472094
> ...
> 17/06/13 05:46:50 DEBUG wire: http-outgoing-2 << "Content-Length: 8[\r][\n]"
> ....
> {noformat}
> Here's what FileScanRDD prints:
> {noformat}
> 17/06/13 05:46:52 INFO FileScanRDD: Reading File path:
> s3://my-bucket/test/part-00004-b8a8a1b7-0581-401f-b520-27fa9600f35e.snappy.parquet,
> range: 0-7473020, partition values: [empty row]
> 17/06/13 05:46:52 INFO FileScanRDD: Reading File path:
> s3://my-bucket/test/part-00011-b8a8a1b7-0581-401f-b520-27fa9600f35e.snappy.parquet,
> range: 0-7472503, partition values: [empty row]
> 17/06/13 05:46:52 INFO FileScanRDD: Reading File path:
> s3://my-bucket/test/part-00006-b8a8a1b7-0581-401f-b520-27fa9600f35e.snappy.parquet,
> range: 0-7472501, partition values: [empty row]
> 17/06/13 05:46:52 INFO FileScanRDD: Reading File path:
> s3://my-bucket/test/part-00007-b8a8a1b7-0581-401f-b520-27fa9600f35e.snappy.parquet,
> range: 0-7473104, partition values: [empty row]
> 17/06/13 05:46:52 INFO FileScanRDD: Reading File path:
> s3://my-bucket/test/part-00003-b8a8a1b7-0581-401f-b520-27fa9600f35e.snappy.parquet,
> range: 0-7472458, partition values: [empty row]
> 17/06/13 05:46:52 INFO FileScanRDD: Reading File path:
> s3://my-bucket/test/part-00012-b8a8a1b7-0581-401f-b520-27fa9600f35e.snappy.parquet,
> range: 0-7472594, partition values: [empty row]
> 17/06/13 05:46:52 INFO FileScanRDD: Reading File path:
> s3://my-bucket/test/part-00001-b8a8a1b7-0581-401f-b520-27fa9600f35e.snappy.parquet,
> range: 0-7472984, partition values: [empty row]
> 17/06/13 05:46:52 INFO FileScanRDD: Reading File path:
> s3://my-bucket/test/part-00014-b8a8a1b7-0581-401f-b520-27fa9600f35e.snappy.parquet,
> range: 0-7472720, partition values: [empty row]
> 17/06/13 05:46:53 INFO FileScanRDD: Reading File path:
> s3://my-bucket/test/part-00008-b8a8a1b7-0581-401f-b520-27fa9600f35e.snappy.parquet,
> range: 0-7472339, partition values: [empty row]
> 17/06/13 05:46:53 INFO FileScanRDD: Reading File path:
> s3://my-bucket/test/part-00015-b8a8a1b7-0581-401f-b520-27fa9600f35e.snappy.parquet,
> range: 0-7472437, partition values: [empty row]
> 17/06/13 05:46:53 INFO FileScanRDD: Reading File path:
> s3://my-bucket/test/part-00013-b8a8a1b7-0581-401f-b520-27fa9600f35e.snappy.parquet,
> range: 0-7472312, partition values: [empty row]
> 17/06/13 05:46:53 INFO FileScanRDD: Reading File path:
> s3://my-bucket/test/part-00002-b8a8a1b7-0581-401f-b520-27fa9600f35e.snappy.parquet,
> range: 0-7472191, partition values: [empty row]
> 17/06/13 05:46:53 INFO FileScanRDD: Reading File path:
> s3://my-bucket/test/part-00005-b8a8a1b7-0581-401f-b520-27fa9600f35e.snappy.parquet,
> range: 0-7472239, partition values: [empty row]
> 17/06/13 05:46:53 INFO FileScanRDD: Reading File path:
> s3://my-bucket/test/part-00000-b8a8a1b7-0581-401f-b520-27fa9600f35e.snappy.parquet,
> range: 0-7472094, partition values: [empty row]
> 17/06/13 05:46:53 INFO FileScanRDD: Reading File path:
> s3://my-bucket/test/part-00010-b8a8a1b7-0581-401f-b520-27fa9600f35e.snappy.parquet,
> range: 0-7471960, partition values: [empty row]
> 17/06/13 05:46:53 INFO FileScanRDD: Reading File path:
> s3://my-bucket/test/part-00009-b8a8a1b7-0581-401f-b520-27fa9600f35e.snappy.parquet,
> range: 0-7471520, partition values: [empty row]
> {noformat}
> Parquet tool info (on one of the files):
> {noformat}
> ~$ parquet-tools meta
> part-00009-b8a8a1b7-0581-401f-b520-27fa9600f35e.snappy.parquet
> file:
> file:/Users/michael/part-00009-b8a8a1b7-0581-401f-b520-27fa9600f35e.snappy.parquet
> creator: parquet-mr version 1.8.1 (build
> 4aba4dae7bb0d4edbcf7923ae1339f28fd3f7fcf)
> extra: org.apache.spark.sql.parquet.row.metadata =
> {"type":"struct","fields":[{"name":"time","type":"long","nullable":false,"metadata":{}},{"name":"country","type":"string","nullable":true,"metadata":{}}]}
> file schema: spark_schema
> --------------------------------------------------------------------------------
> time: REQUIRED INT64 R:0 D:0
> country: OPTIONAL BINARY O:UTF8 R:0 D:1
> row group 1: RC:625000 TS:11201229 OFFSET:4
> --------------------------------------------------------------------------------
> time: INT64 SNAPPY DO:0 FPO:4 SZ:2501723/5000239/2.00 VC:625000
> ENC:PLAIN,BIT_PACKED
> country: BINARY SNAPPY DO:0 FPO:2501727 SZ:4969317/6200990/1.25
> VC:625000 ENC:PLAIN,BIT_PACKED,RLE
> {noformat}
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