Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/11148#discussion_r52825188
--- Diff:
sql/hive/src/main/scala/org/apache/spark/sql/hive/SQLBuilder.scala ---
@@ -80,6 +81,26 @@ class SQLBuilder(logicalPlan: LogicalPlan, sqlContext:
SQLContext) extends Loggi
case p: Limit =>
s"${toSQL(p.child)} LIMIT ${p.limitExpr.sql}"
+ // TABLESAMPLE is part of tableSource clause in the parser,
+ // and thus we must handle it with subquery.
+ case p @ Sample(lb, ub, withReplacement, _, _)
+ if !withReplacement && lb <= (ub + RandomSampler.roundingEpsilon)
=>
+ val fraction = math.min(100, math.max(0, (ub - lb) * 100))
+ p.child match {
+ case m: MetastoreRelation =>
+ val aliasName = m.alias.getOrElse("")
+ build(
+ s"`${m.databaseName}`.`${m.tableName}`",
+ "TABLESAMPLE(" + fraction + " PERCENT)",
+ aliasName)
+ case s: Subquery =>
+ val aliasName = if (s.child.isInstanceOf[Subquery]) s.alias else
""
+ val plan = if (s.child.isInstanceOf[Subquery]) s.child else s
+ build(toSQL(plan), "TABLESAMPLE(" + fraction + " PERCENT)",
aliasName)
+ case _ =>
--- End diff --
Unable to create a test case for this branch. I do not know if we should
throw an exception here or building a SQL.
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