Github user liancheng commented on a diff in the pull request:
https://github.com/apache/spark/pull/7238#discussion_r35085340
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/parquet/newParquet.scala ---
@@ -407,7 +410,17 @@ private[sql] class ParquetRelation2(
val filesToTouch =
if (shouldMergeSchemas) {
// Also includes summary files, 'cause there might be empty
partition directories.
- (metadataStatuses ++ commonMetadataStatuses ++
dataStatuses).toSeq
+
+ // If skipMergePartFiles config is true, we assume that all
part-files are the same for
+ // their schema with summary files, so we ignore them when
merging schema.
+ // If the config is false, which is the default setting, we
merge all part-files.
+ val needMerged: Seq[FileStatus] =
--- End diff --
So, if I understand this correctly, `skipMergePartFiles` is useful when
dealing with partitioned tables, where each partition directory may contain its
own summary files, right? Namely something like this:
```
.
âââ p=1
â  âââ _metadata
â  âââ _common_metadata
â  âââ ...
âââ p=2
âââ _common_metadata
âââ _metadata
âââ ...
```
And for non-partitioned tables, `skipMergePartFiles` essentially disables
`shouldMergeSchemas`, is it correct?
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