Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/20072#discussion_r160077189
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala ---
@@ -263,6 +263,17 @@ object SQLConf {
.booleanConf
.createWithDefault(false)
+ val DISK_TO_MEMORY_SIZE_FACTOR = buildConf(
+ "spark.sql.sources.compressionFactor")
+ .internal()
+ .doc("The result of multiplying this factor with the size of data
source files is propagated " +
+ "to serve as the stats to choose the best execution plan. In the
case where the " +
--- End diff --
`When estimating the output data size of a table scan, multiple the file
size with this factor as the estimated data size, in case the data is
compressed in the file and lead to a heavily underestimated result.`
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