xuzifu666 commented on code in PR #4431:
URL: https://github.com/apache/calcite/pull/4431#discussion_r2161552178
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testkit/src/main/java/org/apache/calcite/test/SqlOperatorTest.java:
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@@ -2565,6 +2568,17 @@ private static void checkConcatFunc(SqlOperatorFixture
f) {
f.checkString("concat('', '', 'a')", "a", "VARCHAR(1) NOT NULL");
f.checkString("concat('', '', '')", "", "VARCHAR(0) NOT NULL");
f.checkFails("^concat()^", INVALID_ARGUMENTS_NUMBER, false);
+
+ // test for ByteString
+ f.checkString("concat(x'61',x'62')", "0x6162", "VARCHAR(2) NOT NULL");
+ f.checkString("concat(cast(x'61' as binary), cast(x'62' as binary), "
+ + "cast(x'63' as binary))", "0x616263", "VARCHAR(3) NOT NULL");
Review Comment:
I have considered this precision issue before, but the concat function
supports int/double/... (all types that can be cast as string) not only
```string/binary``` types. Even if we define a ```SqlReturnTypeInference```, we
cannot accurately calculate the exact precision of the int type.
For example, for ```INT```, we can only get the precision of 10 from type.
eg ```concat(x'61', 1, 'a')```, the type sequence we get is ```binary(1),
int(10), char(1)```, It would definitely unreasonable to infer the length of
12, so I think VARCHAR_NULLABLE can only be used at this position. Choosing
this ReturnTypes should not affect the result, such as ```SqlFunction
BASE64```. If you have other suggestions also can tell me.
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