tanclary commented on code in PR #3258:
URL: https://github.com/apache/calcite/pull/3258#discussion_r1231279122
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core/src/main/java/org/apache/calcite/runtime/SqlFunctions.java:
##########
@@ -792,6 +792,16 @@ public static String concatMulti(String... args) {
return String.join("", args);
}
+ /** SQL {@code CONCAT(arg0, ...)} function which can accept null
Review Comment:
sorry what is emprt?
##########
core/src/test/java/org/apache/calcite/test/SqlFunctionsTest.java:
##########
@@ -149,6 +151,24 @@ static <E> List<E> list() {
assertThat(concatWithNull(null, "b"), is("b"));
}
+ @Test void testConcatMulti() {
+ assertThat(concatMulti("a b", "cd", "e"), is("a bcde"));
+ // The code generator will ensure that nulls are never passed in. If we
+ // pass in null, it is treated like the string "null", as the following
+ // tests show. Not the desired behavior for SQL.
+ assertThat(concatMulti((String) null), is("null"));
+ assertThat(concatMulti((String) null, null), is("nullnull"));
+ assertThat(concatMulti("a", null, "b"), is("anullb"));
+ }
+
+ @Test void testConcatMultiWithNull() {
+ assertThat(concatMultiWithNull("a b", "cd", "e"), is("a bcde"));
+ // Null value could be passed in which is treated as empty string.
+ assertThat(concatMultiWithNull((String) null), is(""));
Review Comment:
Just to clarify, which of these tests mimics the behavior that BigQuery
follows? My understanding is that BigQuery does the following:
`CONCAT(null, null)` returns `NULL` while
`CONCAT("", "")` returns `""`
##########
core/src/main/java/org/apache/calcite/sql/fun/SqlLibraryOperators.java:
##########
@@ -831,16 +831,43 @@ static RelDataType deriveTypeSplit(SqlOperatorBinding
operatorBinding,
new SqlLikeOperator("NOT RLIKE", SqlKind.RLIKE, true, true);
/** The "CONCAT(arg, ...)" function that concatenates strings.
- * For example, "CONCAT('a', 'bc', 'd')" returns "abcd". */
- @LibraryOperator(libraries = {MYSQL, POSTGRESQL, BIG_QUERY})
+ * For example, "CONCAT('a', 'bc', 'd')" returns "abcd".
+ *
+ * <p>It accepts at least 1 argument and returns null if any of
+ * the arguments is null. */
+ @LibraryOperator(libraries = {MYSQL, BIG_QUERY})
public static final SqlFunction CONCAT_FUNCTION =
SqlBasicFunction.create("CONCAT",
ReturnTypes.MULTIVALENT_STRING_SUM_PRECISION_NULLABLE,
- OperandTypes.repeat(SqlOperandCountRanges.from(2),
+ OperandTypes.repeat(SqlOperandCountRanges.from(1),
OperandTypes.STRING),
SqlFunctionCategory.STRING)
.withOperandTypeInference(InferTypes.RETURN_TYPE);
+ /** The "CONCAT(arg, ...)" function that concatenates strings,
+ * which never returns null.
+ * For example, "CONCAT('a', 'bc', 'd')" returns "abcd".
+ *
+ * <p>If one of the arguments is null, it will be treated as empty string.
+ * "CONCAT('a', null)" returns "a".
+ * "CONCAT('a', null, 'b')" returns "ab".
+ *
+ * <p>Returns empty string only when all arguments are null.
+ * "CONCAT(null)" returns "".
+ * "CONCAT(null, null, null)" returns "".
+ *
+ * <p>It differs from {@link #CONCAT_FUNCTION} when processing
+ * null values. */
+ @LibraryOperator(libraries = {MSSQL, POSTGRESQL})
+ public static final SqlFunction CONCAT_FUNCTION_WITH_NULL =
+ SqlBasicFunction.create("CONCAT",
+ ReturnTypes.MULTIVALENT_STRING_SUM_PRECISION_NOT_NULLABLE,
+ OperandTypes.repeat(SqlOperandCountRanges.from(1),
+ OperandTypes.STRING),
+ SqlFunctionCategory.STRING)
+ .withOperandTypeInference(InferTypes.RETURN_TYPE)
+ .withKind(SqlKind.CONCAT_WITH_NULL);
Review Comment:
is there a SqlKind.CONCAT? What is the advantage of having multiply SqlKind
entries?
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