narendly commented on a change in pull request #731: Add TrieRoutingData
constructor
URL: https://github.com/apache/helix/pull/731#discussion_r376245143
##########
File path:
helix-rest/src/main/java/org/apache/helix/rest/metadatastore/TrieRoutingData.java
##########
@@ -124,8 +128,91 @@ private TrieNode findTrieNode(String path, boolean
findLeafAlongPath)
return curNode;
}
- // TODO: THE CLASS WILL BE CHANGED TO PRIVATE ONCE THE CONSTRUCTOR IS
CREATED.
- static class TrieNode {
+ /**
+ * Checks for the edge case when the only sharding key in provided routing
data is the delimiter
+ * or an empty string. When this is the case, the trie is valid and contains
only one node, which
+ * is the root node, and the root node is a leaf node with a realm address
associated with it.
+ * @param routingData - a mapping from "sharding keys" to "realm addresses"
to be parsed into a
+ * trie
+ * @return whether the edge case is true
+ */
+ private boolean isRootShardingKey(Map<String, List<String>> routingData) {
+ if (routingData.values().size() == 1) {
+ for (List<String> shardingKeys : routingData.values()) {
+ return shardingKeys.size() == 1
+ && (shardingKeys.get(0).equals(DELIMITER) ||
shardingKeys.get(0).equals(""));
+ }
+ }
+
+ return false;
+ }
+
+ /**
+ * Constructs a trie based on the provided routing data. It loops through
all sharding keys and
+ * construct the trie in a top down manner.
+ * @param routingData- a mapping from "sharding keys" to "realm addresses"
to be parsed into a
+ * * trie
+ * @throws InvalidRoutingDataException - when there is an empty sharding key
(edge case that
+ * always renders the routing data invalid); when there is a
sharding key which already
+ * contains a sharding key (invalid); when there is a sharding key
that is a part of
+ * another sharding key (invalid)
+ */
+ private void constructTrie(Map<String, List<String>> routingData)
+ throws InvalidRoutingDataException {
+ for (Map.Entry<String, List<String>> entry : routingData.entrySet()) {
+ for (String shardingKey : entry.getValue()) {
+ // Add a leading delimiter if there isn't any
+ if (!shardingKey.substring(0, 1).equals(DELIMITER)) {
+ shardingKey = DELIMITER + shardingKey;
+ }
+
+ // Root can only be a sharding key if it's the only sharding key.
Since this method is
+ // running, the special case has already been checked, therefore it's
definitely invalid
+ if (shardingKey.equals(DELIMITER)) {
+ throw new InvalidRoutingDataException(
+ "There exists other sharding keys. Root cannot be a sharding
key.");
+ }
+
+ // Locate the next delimiter
+ int nextDelimiterIndex = shardingKey.indexOf(DELIMITER, 1);
Review comment:
@NealSun96
Can you do a quick analysis here - one method would require the
reader/traverser to keep track of the nodes it's traversing and construct a
path, and the implementation you're providing here is "caching" the path in the
name. Which one makes more sense? Think in the context of what kind of
operations would be called more frequently - as in is there a real benefit to
caching?
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