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Posted to issues@spark.apache.org by "Mathieu DESPRIEE (JIRA)" <ji...@apache.org> on 2018/01/22 15:00:04 UTC
[jira] [Comment Edited] (SPARK-20927) Add cache operator to
Unsupported Operations in Structured Streaming
[ https://issues.apache.org/jira/browse/SPARK-20927?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16334363#comment-16334363 ]
Mathieu DESPRIEE edited comment on SPARK-20927 at 1/22/18 2:59 PM:
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@[~zsxwing] actually it does make sense to cache mini-batches that have been fetched from the source.
In our case, we use FileStreamSource to obtain some data in a streaming way from a remote source (s3). It appears that new files get downloaded over and over and over for each streaming query we do on the stream. cache() would improve a lot our processing time.
We also occasionally reprocess some historical data (in a streaming way, using the same queries). The penalty of fetching the data multiple times is off-the-roof ...
was (Author: mathieude):
@[~zsxwing] actually it does make sens to cache mini-batches that have been fetched from the source.
In our case, we use FileStreamSource to obtain some data in a streaming way from a remote source (s3). It appears that new files get downloaded over and over and over for each streaming query we do on the stream. cache() would improve a lot our processing time.
We also occasionally reprocess some historical data (in a streaming way, using the same queries). The penalty of fetching the data multiple times is off-the-roof ...
> Add cache operator to Unsupported Operations in Structured Streaming
> ---------------------------------------------------------------------
>
> Key: SPARK-20927
> URL: https://issues.apache.org/jira/browse/SPARK-20927
> Project: Spark
> Issue Type: Improvement
> Components: Structured Streaming
> Affects Versions: 2.2.0
> Reporter: Jacek Laskowski
> Priority: Trivial
> Labels: starter
>
> Just [found out|https://stackoverflow.com/questions/42062092/why-does-using-cache-on-streaming-datasets-fail-with-analysisexception-queries] that {{cache}} is not allowed on streaming datasets.
> {{cache}} on streaming datasets leads to the following exception:
> {code}
> scala> spark.readStream.text("files").cache
> org.apache.spark.sql.AnalysisException: Queries with streaming sources must be executed with writeStream.start();;
> FileSource[files]
> at org.apache.spark.sql.catalyst.analysis.UnsupportedOperationChecker$.org$apache$spark$sql$catalyst$analysis$UnsupportedOperationChecker$$throwError(UnsupportedOperationChecker.scala:297)
> at org.apache.spark.sql.catalyst.analysis.UnsupportedOperationChecker$$anonfun$checkForBatch$1.apply(UnsupportedOperationChecker.scala:36)
> at org.apache.spark.sql.catalyst.analysis.UnsupportedOperationChecker$$anonfun$checkForBatch$1.apply(UnsupportedOperationChecker.scala:34)
> at org.apache.spark.sql.catalyst.trees.TreeNode.foreachUp(TreeNode.scala:127)
> at org.apache.spark.sql.catalyst.analysis.UnsupportedOperationChecker$.checkForBatch(UnsupportedOperationChecker.scala:34)
> at org.apache.spark.sql.execution.QueryExecution.assertSupported(QueryExecution.scala:63)
> at org.apache.spark.sql.execution.QueryExecution.withCachedData$lzycompute(QueryExecution.scala:74)
> at org.apache.spark.sql.execution.QueryExecution.withCachedData(QueryExecution.scala:72)
> at org.apache.spark.sql.execution.QueryExecution.optimizedPlan$lzycompute(QueryExecution.scala:78)
> at org.apache.spark.sql.execution.QueryExecution.optimizedPlan(QueryExecution.scala:78)
> at org.apache.spark.sql.execution.QueryExecution.sparkPlan$lzycompute(QueryExecution.scala:84)
> at org.apache.spark.sql.execution.QueryExecution.sparkPlan(QueryExecution.scala:80)
> at org.apache.spark.sql.execution.QueryExecution.executedPlan$lzycompute(QueryExecution.scala:89)
> at org.apache.spark.sql.execution.QueryExecution.executedPlan(QueryExecution.scala:89)
> at org.apache.spark.sql.execution.CacheManager$$anonfun$cacheQuery$1.apply(CacheManager.scala:104)
> at org.apache.spark.sql.execution.CacheManager.writeLock(CacheManager.scala:68)
> at org.apache.spark.sql.execution.CacheManager.cacheQuery(CacheManager.scala:92)
> at org.apache.spark.sql.Dataset.persist(Dataset.scala:2603)
> at org.apache.spark.sql.Dataset.cache(Dataset.scala:2613)
> ... 48 elided
> {code}
> It should be included in Structured Streaming's [Unsupported Operations|http://spark.apache.org/docs/latest/structured-streaming-programming-guide.html#unsupported-operations].
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