Github user windpiger commented on the issue:
https://github.com/apache/spark/pull/15668
@cloud-fan yes,It is simpler,I check the query plan, my test case
`sql("SELECTpercentile_approx(key, 0.99999)" +
", count(distinct key),sum(distinct key) FROM src LIMIT 1")`
explain is ok as follows:
`+- *Expand [List(null, null, 0, cast(key#29 as double)), List(key#29,
null, 1, null), List(null, cast(key#29 as bigint), 2, null)], [src.`key`#38,
CAST(src.`key` AS BIGINT)#39L, gid#37, CAST(src.`key` AS DOUBLE)#40]
+- HiveTableScan [key#29], MetastoreRelation
default, src`
But, I miss one case that the distinct on a constant like:
`sql("SELECTpercentile_approx(key, 0.99999)" +
", count(distinct key),sum(distinct key),count(distinct 1) FROM src
LIMIT 1")`
explain with a literal expand as follows:
`+- *Expand [List(null, null, null, 0, cast(key#69 as double)), List(1,
null, null, 1, null), List(null, key#69, null, 2, null), List(null, null,
cast(key#69 as bigint), 3, null)], [src.`key`#80, CAST(src.`key` AS
BIGINT)#81L, gid#79, CAST(src.`key` AS DOUBLE)#82]
+- HiveTableScan [key#69], MetastoreRelation
default, src`
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