[GitHub] [druid] sthetland commented on a change in pull request #9488: Match GREATEST/LEAST function behavior to other DBs

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sthetland commented on a change in pull request #9488: Match GREATEST/LEAST function behavior to other DBs
URL: https://github.com/apache/druid/pull/9488#discussion_r390011472
 
 

 ##########
 File path: docs/misc/math-expr.md
 ##########
 @@ -181,6 +181,22 @@ See javadoc of java.lang.Math for detailed explanation for each function.
 | all(lambda,arr) | returns 1 if all elements in the array matches the lambda expression, else 0 |
 
 
+### Reduction functions
+
+Reduction functions operate on zero or more expressions and return a single expression. If no expressions are passed
+as arguments, then the result is `NULL`. The expressions must all be convertible to a
+common data type, which will be the type of the result:
+*  If any argument is `NULL`, the result is `NULL`.
+*  If the arguments comprise a mix of numbers and strings, the arguments are interpreted as strings.
+*  If all arguments are integer numbers, the arguments are interpreted as longs.
+*  If all arguments are numbers and at least one argument is a double, the arguments are interpreted as doubles. 
+
+| function | description |
+| --- | --- |
+| greatest([expr1, ...]) | Returns the maximum expression across zero or more expressions. |
+| least([expr1, ...]) | Returns the minimum expression across zero or more expressions. |
 
 Review comment:
   ```suggestion
   | least([expr1, ...]) | Returns the smallest value among zero or more expressions. |
   ```

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