stevenzwu commented on code in PR #16174:
URL: https://github.com/apache/iceberg/pull/16174#discussion_r3237937573
##########
core/src/main/java/org/apache/iceberg/util/LocationUtil.java:
##########
@@ -57,4 +57,59 @@ public static String tableLocation(TableIdentifier
tableIdentifier, boolean useU
return tableIdentifier.name();
}
}
+
+ /**
+ * Returns true if the location contains a URI scheme (e.g. {@code s3:},
{@code hdfs:}, {@code
+ * file:}), per <a
href="https://datatracker.ietf.org/doc/html/rfc3986#section-3.1";>RFC 3986
+ * section 3.1</a>.
+ */
+ private static boolean hasScheme(String location) {
+ if (location.isEmpty()) {
+ return false;
+ }
+
+ // Early termination for relative locations since most commonly start with
/
+ if (location.charAt(0) == '/') {
+ return false;
+ }
+
+ for (int i = 0; i < location.length(); i += 1) {
+ char ch = location.charAt(i);
+ if (ch == ':') {
+ return i > 0;
+ }
+
+ if (!Character.isLetterOrDigit(ch) && ch != '+' && ch != '-' && ch !=
'.') {
+ return false;
+ }
+ }
+
+ return false;
+ }
+
+ /**
+ * Resolves a relative location against a table location. If the location
has a URI scheme, it is
+ * returned as-is. Otherwise, the location is appended to the table location
without any
+ * additional separator.
+ */
+ public static String resolveLocation(String tableLocation, String location) {
+ if (hasScheme(location)) {
+ return location;
+ }
+
+ return tableLocation + location;
+ }
+
+ /**
+ * Relativizes a location against a table location. If the location starts
with the table
+ * location, the prefix is removed and the remaining relative portion is
returned. Otherwise, the
+ * location is returned as-is.
+ */
+ public static String relativizeLocation(String tableLocation, String
location) {
+ if (location.startsWith(tableLocation)) {
Review Comment:
> This scenario should resolve to an absolute path
Great. This is the first thing that we need to agree on.
> but I don't think we can provide a concrete solution without relying on a
separator character.
This is the tricky part. The location is an URI (not a s3 object key
string). It might be reasonable to assume `/` as a separator character for
hierarchies?
[The spec](https://github.com/apache/iceberg/pull/15630/changes) already
mentioned the path separator. Can we require that the `relative portion`
**must** start with the path separator?
```
Paths used as prefixes must not end in a path separator. The relative
portion is appended to the prefix without introduction of any additional
separator characters.
```
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