Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/21250#discussion_r186438139
--- Diff: docs/sparkr.md ---
@@ -663,3 +663,7 @@ You can inspect the search path in R with
[`search()`](https://stat.ethz.ch/R-ma
- The `stringsAsFactors` parameter was previously ignored with `collect`,
for example, in `collect(createDataFrame(iris), stringsAsFactors = TRUE))`. It
has been corrected.
- For `summary`, option for statistics to compute has been added. Its
output is changed from that from `describe`.
- A warning can be raised if versions of SparkR package and the Spark JVM
do not match.
+
+## Upgrading to SparkR 2.3.1 and above
+
+ - In SparkR 2.3.0 and earlier, the `start` parameter of `substr` method
was wrongly subtracted by one, previously. In other words, the index specified
by `start` parameter was considered as 0-base. This can lead to inconsistent
substring results and also does not match with the behaviour with `substr` in
R. In version 2.3.1 and later, it has been fixed so the `start` parameter of
`substr` method is now 1-base. As an example, `substr(lit('abcdef'), 2, 4))`
would result to `abc` in SparkR 2.3.0, and the result would be `bcd` in SparkR
2.3.1.
--- End diff --
a little simplification:
```
the `start` parameter of `substr` method was wrongly subtracted by one and
considered as 0-based. This leads to ...
```
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