Michael Allman created SPARK-25894: -------------------------------------- Summary: Include a count of the number of physical columns read for a columnar data source in the metadata of FileSourceScanExec Key: SPARK-25894 URL: https://issues.apache.org/jira/browse/SPARK-25894 Project: Spark Issue Type: Improvement Components: SQL Affects Versions: 2.4.0 Reporter: Michael Allman
Knowing the number of physical columns Spark will read from a columnar file format (such as Parquet) is extremely helpful (if not critical) in validating an assumption about that number of columns based on a given query and schema pruning functionality. For example, take a {{contacts}} table with a {{name}} struct like {{name.first, name.last}}. Without schema pruning the following query reads both columns in the {{name}} struct: {{select name.first from contacts}} With schema pruning, the same query reads only the {{name.first}} column. This issue (and related PR) proposes an additional metadata field for {{FileSourceScanExec}} which identifies the number of columns Spark will read from that file source. This metadata will be printed as part of a physical plan explanation. -- This message was sent by Atlassian JIRA (v7.6.3#76005) --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@spark.apache.org For additional commands, e-mail: issues-h...@spark.apache.org