[GitHub] [spark] JoshRosen opened a new pull request #24668: [SPARK-27676][SQL] InMemoryFileIndex should respect spark.sql.files.ignoreMissingFiles

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JoshRosen opened a new pull request #24668: [SPARK-27676][SQL] InMemoryFileIndex should respect spark.sql.files.ignoreMissingFiles
URL: https://github.com/apache/spark/pull/24668
 
 
   ## What changes were proposed in this pull request?
   
   Spark's `InMemoryFileIndex` contains two places where `FileNotFound` exceptions are caught and logged as warnings (during [directory listing](https://github.com/apache/spark/blob/bcd3b61c4be98565352491a108e6394670a0f413/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/InMemoryFileIndex.scala#L274) and [block location lookup](https://github.com/apache/spark/blob/bcd3b61c4be98565352491a108e6394670a0f413/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/InMemoryFileIndex.scala#L333)). This logic was added in #15153 and #21408.
   
   I think that this is a dangerous default behavior because it can mask bugs caused by race conditions (e.g. overwriting a table while it's being read) or S3 consistency issues (there's more discussion on this in the [JIRA ticket](https://issues.apache.org/jira/browse/SPARK-27676)). Failing fast when we detect missing files is not sufficient to make concurrent table reads/writes or S3 listing safe (there are other classes of eventual consistency issues to worry about), but I think it's still beneficial to throw exceptions and fail-fast on the subset of inconsistencies / races that we _can_ detect because that increases the likelihood that an end user will notice the problem and investigate further.
   
   There may be some cases where users _do_ want to ignore missing files, but I think that should be an opt-in behavior via the existing `spark.sql.files.ignoreMissingFiles` flag (the current behavior is itself race-prone because a file might be be deleted between catalog listing and query execution time, triggering FileNotFoundExceptions on executors (which are handled in a way that _does_ respect `ignoreMissingFIles`)).
   
   This PR updates `InMemoryFileIndex` to guard the log-and-ignore-FileNotFoundException behind the existing `spark.sql.files.ignoreMissingFiles` flag.
   
   **Note**: this is a change of default behavior, so I think it needs to be mentioned in release notes.
   
   ## How was this patch tested?
   
   Updated existing test case to test with the `ignoreMissingFIles` flag (both true and false).

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