rubenada commented on code in PR #3237:
URL: https://github.com/apache/calcite/pull/3237#discussion_r1223065806
##########
core/src/main/java/org/apache/calcite/runtime/SqlFunctions.java:
##########
@@ -4102,6 +4102,43 @@ public static List reverse(List list) {
return list;
}
+ /** SQL {@code ARRAY_TO_STRING(array, delimiter)} function. */
+ public static String arrayToString(List list, String delimiter) {
+ return arrayToString(list, delimiter, null);
+ }
+
+ /** SQL {@code ARRAY_TO_STRING(array, delimiter, nullText)} function. */
+ public static String arrayToString(List list, String delimiter, @Nullable
String nullText) {
+ StringBuilder sb = new StringBuilder();
+ for (Object item : list) {
+ String str;
+ if (item == null) {
+ str = null;
+ } else if (item instanceof String) {
+ str = (String) item;
+ } else if (item instanceof ByteString) {
+ str = item.toString();
+ } else {
+ throw new IllegalStateException(
+ "arrayToString supports only String or ByteString, but got "
+ + item.getClass().getName());
+ }
+ if (str == null) {
+ if (nullText == null) {
+ continue;
+ } else {
+ str = nullText;
+ }
+ }
+
+ if (sb.length() > 0) {
Review Comment:
Sorry @zoudan , one last detail (rather an edge case): what is the expected
behavior if the item (`str` in this point) is the empty string? Will it be
appended like any other value with the corresponding delimiter before the
precious value?
For example:
```
array_to_string(array['', 'b'], '-') => '-b' ???
array_to_string(array['', ''], '-') => '-' ???
```
If that is the case, I have the impression that this condition is wrong and
we would need to find another mechanism, e.g.
```
boolean first = true;
for (Object item : list) {
...
if (!first) {
sb.append(delimiter);
}
sb.append(str);
first = false;
}
```
wdyt?
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