deniskuzZ commented on code in PR #6642:
URL: https://github.com/apache/hive/pull/6642#discussion_r3764587110
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ql/src/java/org/apache/hadoop/hive/ql/metadata/Hive.java:
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@@ -5170,6 +5189,110 @@ private static String getPathName(int taskId) {
return Utilities.replaceTaskId("000000", taskId) + "_0";
}
+ /**
+ * Compute a compact per-query uniqueness tag used by the non-ACID rename
branch of
+ * {@link #mvFile} to make each concurrent writer's destination key unique
on filesystems
+ * whose {@code rename} is not atomic-if-absent. The tag becomes the copy
suffix
+ * ({@code basename_copy_<tag>}) in place of the numeric {@code _copy_N}
counter.
+ * <p>
+ * Reads {@code hive.query.id} from the passed {@link HiveConf} and
delegates to
+ * {@link QueryPlan#extractUniquenessTag(String)} for the actual UUID → hex
derivation.
+ * The shape matches {@link ParsedOutputFileName}'s copy-index group so
downstream filename
+ * parsing (taskId, attemptId, copyIndex) keeps working.
+ */
+ static String computeUniquenessTag(HiveConf conf) {
+ String qid = HiveConf.getVar(conf, ConfVars.HIVE_QUERY_ID);
+ if (Strings.isNullOrEmpty(qid)) {
+ throw new IllegalStateException("hive.query.id is required to derive a
unique destination name");
+ }
+ return QueryPlan.extractUniquenessTag(qid);
+ }
+
+ /**
+ * @return {@code true} when the filesystem's URI scheme is one of the known
non-atomic-rename
+ * schemes ({@link #NON_ATOMIC_RENAME_SCHEMES}); {@code false}
otherwise (including a
+ * {@code null} fs or missing scheme).
+ */
+ static boolean isNonAtomicRenameFs(FileSystem fs) {
+ if (fs == null || fs.getUri() == null || fs.getUri().getScheme() == null) {
+ return false;
+ }
+ return
NON_ATOMIC_RENAME_SCHEMES.contains(fs.getUri().getScheme().toLowerCase());
+ }
+
+ /**
+ * Picks the destination {@link Path} for {@link #mvFile}, choosing between
a per-query
+ * uniqueness-tagged name (on filesystems without atomic rename-if-absent
semantics) and the
+ * legacy {@code _copy_N} counter-based picker.
+ *
+ * <p>On file systems without atomic rename-if-absent semantics (e.g. S3),
two concurrent inserts
+ * targeting the same new dynamic partition race in the counter-based picker
below: their
+ * {@code exists()} probes both fire before either PUT commits, both rename
to the same final
+ * key, and the second PUT silently overwrites the first (last writer wins,
no error surfaces).
+ * To eliminate the collision, on such filesystems we skip the counter-based
{@code _copy_N}
+ * picker entirely and use a per-query uniqueness tag (8-hex derived from
{@code hive.query.id})
+ * as the copy suffix, so two concurrent writers rename to distinct keys.
+ *
+ * <p>The uniqueness-tag path is only taken in the non-ACID rename branch
+ * ({@code taskId == -1 && isRenameAllowed && !isOverwrite}): ACID writers
already own unique
+ * taskIds, copy/copyFromLocal do not race on the destination filename, and
overwrite explicitly
+ * clears the target first.
+ */
+ private static Path pickDestFilePath(HiveConf conf, FileSystem sourceFs,
Path sourcePath, FileSystem destFs,
Review Comment:
should we extract this into `MoveTask` or something? make static util?
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