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Cheng Lian commented on SPARK-11153: ------------------------------------ Good question. We tried, see [PR #9225|https://github.com/apache/spark/pull/9225], but at last decided not to do so. There are several reasons: This issue can be hacked and worked around though. # Parquet-mr 1.8.1 is not in a very good status, while we don't have much time left to test it before 1.6 release. The two major issues we found are: #- We observed performance regression for full Parquet table scanning, but the reason is still unknown yet. #- Parquet-mr 1.8.1 introduced PARQUET-363, which brings performance regression for queries like {{SELECT COUNT(1) FROM t}}. (This issue can be hacked and worked around though.) # Parquet-mr 1.8.1 hasn't been widely deployed yet (e.g. Hive 1.2.1 is still using 1.6.0), which means that most Parquet files out there all suffer the corrupted statistics issue. Thus using parquet-mr 1.7.0 in Spark 1.6 while disabling filter push-down for string/binary columns doesn't bring too much negative impact. > Turns off Parquet filter push-down for string and binary columns > ---------------------------------------------------------------- > > Key: SPARK-11153 > URL: https://issues.apache.org/jira/browse/SPARK-11153 > Project: Spark > Issue Type: Bug > Components: SQL > Affects Versions: 1.5.0, 1.5.1 > Reporter: Cheng Lian > Assignee: Cheng Lian > Priority: Blocker > Fix For: 1.5.2, 1.6.0 > > > Due to PARQUET-251, {{BINARY}} columns in existing Parquet files may be > written with corrupted statistics information. This information is used by > filter push-down optimization. Since Spark 1.5 turns on Parquet filter > push-down by default, we may end up with wrong query results. PARQUET-251 has > been fixed in parquet-mr 1.8.1, but Spark 1.5 is still using 1.7.0. > Note that this kind of corrupted Parquet files could be produced by any > Parquet data models. > This affects all Spark SQL data types that can be mapped to Parquet > {{BINARY}}, namely: > - {{StringType}} > - {{BinaryType}} > - {{DecimalType}} (but Spark SQL doesn't support pushing down {{DecimalType}} > columns for now.) > To avoid wrong query results, we should disable filter push-down for columns > of {{StringType}} and {{BinaryType}} until we upgrade to parquet-mr 1.8. -- This message was sent by Atlassian JIRA (v6.3.4#6332) --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@spark.apache.org For additional commands, e-mail: issues-h...@spark.apache.org