Airblader commented on a change in pull request #17256:
URL: https://github.com/apache/flink/pull/17256#discussion_r709802110
##########
File path: flink-python/pyflink/table/expressions.py
##########
@@ -544,6 +544,26 @@ def if_then_else(condition: Union[bool, Expression[bool]],
if_true, if_false) ->
return _ternary_op("ifThenElse", condition, if_true, if_false)
+def coalesce(*args) -> Expression:
+ """
+ Returns the first argument that is not NULL.
+
+ If all arguments are NULL, it returns NULL as well. The return type is the
least restrictive, common type of all of its arguments.
+ The return type is nullable if all arguments are nullable as well.
+
+ Examples:
+ ::
+
+ >>> coalesce(null, "default") # Returns "default"
+ >>> coalesce(col("f0"), col("f1"), "default") returns the first
non-null value among f0 and f1, or "default" if f0 and f1 are both null.
Review comment:
```suggestion
>>> # Returns the first non-null value among f0 and f1,
>>> # or "default" if f0 and f1 are both null
>>> coalesce(col("f0"), col("f1"), "default") returns the first
non-null value among f0 and f1, or "default" if f0 and f1 are both null.
```
##########
File path: flink-python/pyflink/table/expressions.py
##########
@@ -544,6 +544,26 @@ def if_then_else(condition: Union[bool, Expression[bool]],
if_true, if_false) ->
return _ternary_op("ifThenElse", condition, if_true, if_false)
+def coalesce(*args) -> Expression:
+ """
+ Returns the first argument that is not NULL.
+
+ If all arguments are NULL, it returns NULL as well. The return type is the
least restrictive, common type of all of its arguments.
+ The return type is nullable if all arguments are nullable as well.
+
+ Examples:
+ ::
+
+ >>> coalesce(null, "default") # Returns "default"
Review comment:
Python doesn't have a `null`, I think this would have to be `None`. I
think it's OK to talk about "null" in the docs, but the code example should of
course compile. :-)
```suggestion
>>> coalesce(None, "default") # Returns "default"
```
##########
File path:
flink-table/flink-table-api-scala/src/main/scala/org/apache/flink/table/api/ImplicitExpressionConversions.scala
##########
@@ -726,6 +726,25 @@ trait ImplicitExpressionConversions {
Expressions.ifThenElse(condition, ifTrue, ifFalse)
}
+ /**
+ * Returns the first argument that is not NULL.
+ *
+ * If all arguments are NULL, it returns NULL as well. The return type is
the least
+ * restrictive, common type of all of its arguments. The return type is
nullable if all
+ * arguments are nullable as well.
+ *
+ * For example:
+ *
+ * - `coalesce(null, default")` returns `"default"`.
+ * - `coalesce($"f0", $"f1", "default")` returns the first non-null value
among f0 and f1,
+ * or `"default"` if f0 and f1 are both null
Review comment:
This isn't yet a code block like with Java. There's also a syntax error
in there.
```suggestion
* Examples:
* {{{
* // Returns "default"
* coalesce(null, "default")
*
* // Returns the first non-null value among f0 and f1, or "default" if f0
and f1 are both null
* coalesce($"f0", $"f1", "default")
* }}}
```
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