imay commented on a change in pull request #3439:
URL: https://github.com/apache/incubator-doris/pull/3439#discussion_r420145099
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File path:
docs/en/sql-reference/sql-functions/string-functions/append_trailing_char_if_absent.md
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@@ -0,0 +1,58 @@
+---
+{
+ "title": "append_trailing_char_if_absent",
+ "language": "en"
+}
+---
+
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
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+regarding copyright ownership. The ASF licenses this file
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+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+# append_trailing_char_if_absent
+## description
+### Syntax
+
+`VARCHAR append_trailing_char_if_absent(VARCHAR str, VARCHAR trailing_char)`
+
+If the s string is non-empty and does not contain the c character at the end,
it appends the c character to the end.
+Trailing_char contains only one character, and it will report an error if
contains more than one character
Review comment:
In the case `append_trailing_char_if_absent(str, col1)` in which col1 is
a column of a table. You can not know if the length of col1 is 1 or not.
Also there is no need to keep the same with CK.
It is convention to return null when the argument is invalid in Doris.
So what I suggest is to return null when the input argument is not valid.
And there is no need to check its input in FE.
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