Github user paul-rogers commented on a diff in the pull request:
https://github.com/apache/drill/pull/775#discussion_r104809964
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/work/metadata/ServerMetaProvider.java
---
@@ -76,7 +76,7 @@
.setReadOnly(false)
.setGroupBySupport(GroupBySupport.GB_UNRELATED)
.setLikeEscapeClauseSupported(true)
- .setNullCollation(NullCollation.NC_AT_END)
+ .setNullCollation(NullCollation.NC_HIGH)
--- End diff --
When sorting in Drill, the detailed sort spec is set in the
{{ExternalSort}} operator definition. This thing is a bit complex. One can
control sort order (ASC, DESC) and nulls position (LOW, HIGH, UNSPECIFIED.)
Data sorts according to ASC, DESC.
Nulls sort as follows:
HIGH: last if ASC, first if DESC
LOW: first if ASC, last if DESC
UNSPECIFIED: always high
If the planner has no way of setting the nulls ordering from a SQL query,
then the value is UNSPECIFIED, which means nulls always sort last as Jinfeng
explained.
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