Re: Cache sparkSql data without uncompressing it in memory
Thanks Chneg, Just one more question - does that mean that we still need enough memory in the cluster to uncompress the data before it can be compressed again or does that just read the raw data as is? On Wed, Nov 12, 2014 at 10:05 PM, Cheng Lian lian.cs@gmail.com wrote: Currently there’s no way to cache the compressed sequence file directly. Spark SQL uses in-memory columnar format while caching table rows, so we must read all the raw data and convert them into columnar format. However, you can enable in-memory columnar compression by setting spark.sql.inMemoryColumnarStorage.compressed to true. This property is already set to true by default in master branch and branch-1.2. On 11/13/14 7:16 AM, Sadhan Sood wrote: We noticed while caching data from our hive tables which contain data in compressed sequence file format that it gets uncompressed in memory when getting cached. Is there a way to turn this off and cache the compressed data as is ?
Re: Cache sparkSql data without uncompressing it in memory
No, the columnar buffer is built in a small batching manner, the batch size is controlled by the |spark.sql.inMemoryColumnarStorage.batchSize| property. The default value for this in master and branch-1.2 is 10,000 rows per batch. On 11/14/14 1:27 AM, Sadhan Sood wrote: Thanks Chneg, Just one more question - does that mean that we still need enough memory in the cluster to uncompress the data before it can be compressed again or does that just read the raw data as is? On Wed, Nov 12, 2014 at 10:05 PM, Cheng Lian lian.cs@gmail.com mailto:lian.cs@gmail.com wrote: Currently there’s no way to cache the compressed sequence file directly. Spark SQL uses in-memory columnar format while caching table rows, so we must read all the raw data and convert them into columnar format. However, you can enable in-memory columnar compression by setting |spark.sql.inMemoryColumnarStorage.compressed| to |true|. This property is already set to true by default in master branch and branch-1.2. On 11/13/14 7:16 AM, Sadhan Sood wrote: We noticed while caching data from our hive tables which contain data in compressed sequence file format that it gets uncompressed in memory when getting cached. Is there a way to turn this off and cache the compressed data as is ?
Cache sparkSql data without uncompressing it in memory
We noticed while caching data from our hive tables which contain data in compressed sequence file format that it gets uncompressed in memory when getting cached. Is there a way to turn this off and cache the compressed data as is ?
