Hi Cheng,
on my computer, execute res0.save("xxx", org.apache.spark.sql.SaveMode.
Overwrite) produces:
peilunlee@pllee-mini:~/opt/spark-1.3...rc3-bin-hadoop1$ ls -l xxx
total 32
-rwxrwxrwx 1 peilunlee staff 0 Mar 27 11:29 _SUCCESS*
-rwxrwxrwx 1 peilunlee staff 272 Mar 27 11:29 part-r-00001.parquet*
-rwxrwxrwx 1 peilunlee staff 272 Mar 27 11:29 part-r-00002.parquet*
-rwxrwxrwx 1 peilunlee staff 272 Mar 27 11:29 part-r-00003.parquet*
-rwxrwxrwx 1 peilunlee staff 488 Mar 27 11:29 part-r-00004.parquet*
while res0.save("xxx") produces:
peilunlee@pllee-mini:~/opt/spark-1.3...rc3-bin-hadoop1$ ls -l xxx
total 40
-rwxrwxrwx 1 peilunlee staff 0 Mar 27 11:29 _SUCCESS*
-rwxrwxrwx 1 peilunlee staff 250 Mar 27 11:29 _common_metadata*
-rwxrwxrwx 1 peilunlee staff 272 Mar 27 11:29 part-r-00001.parquet*
-rwxrwxrwx 1 peilunlee staff 272 Mar 27 11:29 part-r-00002.parquet*
-rwxrwxrwx 1 peilunlee staff 272 Mar 27 11:29 part-r-00003.parquet*
-rwxrwxrwx 1 peilunlee staff 488 Mar 27 11:29 part-r-00004.parquet*
On Thu, Mar 26, 2015 at 7:26 PM, Cheng Lian <lian.cs....@gmail.com> wrote:
> I couldn’t reproduce this with the following spark-shell snippet:
>
> scala> import sqlContext.implicits._
> scala> Seq((1, 2)).toDF("a", "b")
> scala> res0.save("xxx", org.apache.spark.sql.SaveMode.Overwrite)
> scala> res0.save("xxx", org.apache.spark.sql.SaveMode.Overwrite)
>
> The _common_metadata file is typically much smaller than _metadata,
> because it doesn’t contain row group information, and thus can be faster to
> read than _metadata.
>
> Cheng
>
> On 3/26/15 12:48 PM, Pei-Lun Lee wrote:
>
> Hi,
>
> When I save parquet file with SaveMode.Overwrite, it never generate
> _common_metadata. Whether it overwrites an existing dir or not.
> Is this expected behavior?
> And what is the benefit of _common_metadata? Will reading performs better
> when it is present?
>
> Thanks,
> --
> Pei-Lun
>
>
>
