julianhyde commented on code in PR #3184:
URL: https://github.com/apache/calcite/pull/3184#discussion_r1182955655
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core/src/main/java/org/apache/calcite/runtime/SqlFunctions.java:
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@@ -3104,23 +3104,106 @@ public static int position(ByteString seek, ByteString
s) {
/** SQL {@code POSITION(seek IN string FROM integer)} function. */
public static int position(String seek, String s, int from) {
- final int from0 = from - 1; // 0-based
- if (from0 > s.length() || from0 < 0) {
+ if (from == 0) {
+ throw RESOURCE.fromNotZero().ex();
+ }
+ // Case when from is positive
+ if (from > 0) {
+ final int from0 = from - 1; // 0-based
+ if (from0 >= s.length() || from0 < 0) {
+ return 0;
+ } else {
+ return s.indexOf(seek, from0) + 1;
+ }
+ }
+ // Case when from is negative
+ final int rightIndex = from + s.length(); // negative position to positive
index
+ if (rightIndex <= 0) {
return 0;
}
-
- return s.indexOf(seek, from0) + 1;
+ return s.substring(0, rightIndex + 1).lastIndexOf(seek) + 1;
}
/** SQL {@code POSITION(seek IN string FROM integer)} function for byte
* strings. */
public static int position(ByteString seek, ByteString s, int from) {
- final int from0 = from - 1;
- if (from0 > s.length() || from0 < 0) {
+ if (from == 0) {
+ throw RESOURCE.fromNotZero().ex();
+ }
+ // Case when from is positive
+ if (from > 0) {
+ final int from0 = from - 1; // 0-based
+ if (from0 >= s.length() || from0 < 0) {
+ return 0;
+ } else {
+ return s.indexOf(seek, from0) + 1;
+ }
+ }
+ // Case when from is negative
+ final int rightIndex = from + s.length();
+ if (rightIndex <= 0) {
return 0;
}
+ int lastIndex = 0;
+ while (lastIndex < rightIndex) {
+ int indexOf = s.substring(lastIndex, rightIndex + 1).indexOf(seek) + 1;
+ if (indexOf == 0) {
+ break;
+ }
+ lastIndex += indexOf;
+ }
+ return lastIndex;
+ }
- return s.indexOf(seek, from0) + 1;
+ /** SQL {@code POSITION(seek, string, from, occurrence)} function. */
+ public static int position(String seek, String s, int from, int occurrence) {
+ if (occurrence == 0) {
+ throw RESOURCE.occurrenceNotZero().ex();
+ }
+ for (int i = 0; i < occurrence; i++) {
Review Comment:
Ok, `from` isn't constant. But is `from > 0` constant? Or, if it isn't,
should it be? That is, if we go into the `else` branch of the `if` on i = 0, we
also want to go into the `else` branch for i = 1 and i = 2.
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