tkalkirill commented on code in PR #4465:
URL: https://github.com/apache/ignite-3/pull/4465#discussion_r1778473990
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modules/metastorage/src/main/java/org/apache/ignite/internal/metastorage/server/KeyValueStorage.java:
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@@ -233,13 +234,31 @@ boolean invoke(
void removeWatch(WatchListener listener);
/**
- * Compacts storage (removes tombstones).
+ * Compacts outdated key versions and removes tombstones of metastorage
locally.
*
- * @param lowWatermark A time threshold for the entry. Only entries that
have revisions with timestamp higher or equal to the
- * watermark can be removed.
+ * <p>We do not compact the only and last version of the key unless it is
a tombstone.</p>
+ *
+ * <p>Let's look at some examples, let's say we have the following keys
with their versions:</p>
+ * <ul>
+ * <li>Key "foo" with versions that have revisions (1, 3, 5) - "foo"
[1, 3, 5].</li>
+ * <li>Key "bar" with versions that have revisions (1, 2, 5) the last
revision is a tombstone - "bar" [1, 2, 5 tomb].</li>
+ * </ul>
+ *
+ * <p>Let's look at examples of invoking the current method and what will
be in the storage after:</p>
+ * <ul>
+ * <li>Compaction revision is {@code 1}: "foo" [3, 5], "bar" [2, 5
tomb].</li>
+ * <li>Compaction revision is {@code 2}: "foo" [3, 5], "bar" [5
tomb].</li>
+ * <li>Compaction revision is {@code 3}: "foo" [5], "bar" [5
tomb].</li>
+ * <li>Compaction revision is {@code 4}: "foo" [5], "bar" [5
tomb].</li>
+ * <li>Compaction revision is {@code 5}: "foo" [5].</li>
+ * <li>Compaction revision is {@code 6}: "foo" [5].</li>
+ * </ul>
+ *
+ * @param revision Revision up to which the metastorage keys will be
compacted.
Review Comment:
thanks
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