Github user ron8hu commented on a diff in the pull request: https://github.com/apache/spark/pull/17415#discussion_r108583109 --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/statsEstimation/FilterEstimation.scala --- @@ -515,8 +530,135 @@ case class FilterEstimation(plan: Filter, catalystConf: CatalystConf) extends Lo Some(percent.toDouble) } + /** + * Returns a percentage of rows meeting a binary comparison expression containing two columns. + * In SQL queries, we also see predicate expressions involving two columns + * such as "column-1 (op) column-2" where column-1 and column-2 belong to same table. + * Note that, if column-1 and column-2 belong to different tables, then it is a join + * operator's work, NOT a filter operator's work. + * + * @param op a binary comparison operator such as =, <, <=, >, >= + * @param attrLeft the left Attribute (or a column) + * @param attrRight the right Attribute (or a column) + * @param update a boolean flag to specify if we need to update ColumnStat of a given column + * for subsequent conditions + * @return an optional double value to show the percentage of rows meeting a given condition + */ + def evaluateBinaryForTwoColumns( + op: BinaryComparison, + attrLeft: Attribute, + attrRight: Attribute, + update: Boolean): Option[Double] = { + + if (!colStatsMap.contains(attrLeft)) { + logDebug("[CBO] No statistics for " + attrLeft) + return None + } + if (!colStatsMap.contains(attrRight)) { + logDebug("[CBO] No statistics for " + attrRight) + return None + } + + attrLeft.dataType match { + case StringType | BinaryType => --- End diff -- The current code is written in such a way that we do not have too deep indentation. Some engineers do not like deep indentation as they often put screen monitor vertically. Let's handle it when the need occurs. I think, with good test case coverage, we will be able to catch anything we miss.
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