NealSun96 commented on a change in pull request #731: Add TrieRoutingData
constructor
URL: https://github.com/apache/helix/pull/731#discussion_r376165166
##########
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);
+ int prevDelimiterIndex = 0;
+ String keySection = shardingKey.substring(prevDelimiterIndex + 1,
+ nextDelimiterIndex > 0 ? nextDelimiterIndex :
shardingKey.length());
+ TrieNode curNode = _rootNode;
+ TrieNode nextNode = curNode._children.get(keySection);
+
+ // If the key section is not the last section yet, perform the
following
+ while (nextDelimiterIndex > 0) {
+ // If the node is already a leaf node, the current sharding key is
invalid
+ if (nextNode != null && nextNode._isLeaf) {
+ throw new InvalidRoutingDataException(shardingKey.substring(0,
nextDelimiterIndex)
+ + " is already a sharding key. " + shardingKey + " cannot be a
sharding key.");
+ } else if (nextNode == null) {
+ nextNode = new TrieNode(new HashMap<>(), shardingKey.substring(0,
nextDelimiterIndex),
+ false, "");
+ curNode._children.put(keySection, nextNode);
+ }
+ prevDelimiterIndex = nextDelimiterIndex;
+ nextDelimiterIndex = shardingKey.indexOf(DELIMITER,
prevDelimiterIndex + 1);
+ keySection = shardingKey.substring(prevDelimiterIndex + 1,
+ nextDelimiterIndex > 0 ? nextDelimiterIndex :
shardingKey.length());
+ curNode = nextNode;
+ nextNode = curNode._children.get(keySection);
+ }
+
+ // If the last node already exists, it's a part of another sharding
key, making the current
+ // sharding key invalid
+ if (nextNode != null) {
+ throw new InvalidRoutingDataException(shardingKey
+ + " is a part of another sharding key, therefore it cannot be a
sharding key.");
+ }
+ nextNode = new TrieNode(new HashMap<>(), shardingKey, true,
entry.getKey());
Review comment:
I think it's more flexible to allow the direct assignment of children. If
somehow we need to assign existing children in the future as we are
constructing, taking the parameter out now means I have to modify the
constructor later.
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