ArafatKhan2198 commented on code in PR #6969:
URL: https://github.com/apache/ozone/pull/6969#discussion_r1795880267
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hadoop-ozone/recon/src/main/java/org/apache/hadoop/ozone/recon/ReconUtils.java:
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@@ -596,6 +600,70 @@ public static long convertToEpochMillis(String dateString,
String dateFormat, Ti
}
}
+ /**
+ * Retrieves keys from the specified table based on pagination and prefix
filtering.
+ * This method handles different scenarios based on the presence of
startPrefix and prevKey,
+ * enabling efficient key retrieval from the table.
+ *
+ * The method handles the following cases:
+ *
+ * 1. prevKey provided, startPrefix empty:
+ * - Seeks to prevKey, skips it, and returns subsequent records up to the
limit.
+ *
+ * 2. prevKey empty, startPrefix empty:
+ * - Iterates from the beginning of the table, retrieving all records up to
the limit.
+ *
+ * 3. startPrefix provided, prevKey empty:
+ * - Seeks to the first key matching startPrefix and returns all matching
keys up to the limit.
+ *
+ * 4. startPrefix provided, prevKey provided:
+ * - Seeks to prevKey, skips it, and returns subsequent keys that match
startPrefix, up to the limit.
+ *
+ * If limit is 0, all matching keys are retrieved. If both startPrefix and
prevKey are empty, the method starts
+ * from the beginning of the table.
+ */
+ public static <T> Map<String, T> extractKeysFromTable(
+ Table<String, T> table, String startPrefix, int limit, String prevKey)
+ throws IOException {
+
+ Map<String, T> matchedKeys = new LinkedHashMap<>();
+ try (TableIterator<String, ? extends Table.KeyValue<String, T>> keyIter =
table.iterator()) {
+
+ // Scenario 1 & 4: prevKey is provided (whether startPrefix is empty or
not)
+ if (!prevKey.isEmpty()) {
+ keyIter.seek(prevKey);
+ if (keyIter.hasNext()) {
+ // Skip the previous key record
+ keyIter.next();
+ }
+ } else if (!startPrefix.isEmpty()) {
+ // Scenario 3: startPrefix is provided but prevKey is empty, so seek
to startPrefix
+ keyIter.seek(startPrefix);
+ }
+ // Scenario 2: Both startPrefix and prevKey are empty (iterate from the
start of the table)
+ // No seeking needed; just start iterating from the first record in the
table
+ // This is implicit in the following loop, as the iterator will start
from the beginning
+
+ // Iterate through the keys while adhering to the limit (if the limit is
not zero)
+ while (keyIter.hasNext() && (limit == 0 || matchedKeys.size() < limit)) {
Review Comment:
Thanks taken care of this inside `extractKeysFromTable` method of ReconUtils.
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