richardstartin commented on a change in pull request #8394:
URL: https://github.com/apache/pinot/pull/8394#discussion_r833802691
##########
File path:
pinot-segment-local/src/main/java/org/apache/pinot/segment/local/recordtransformer/ExpressionTransformer.java
##########
@@ -60,29 +66,41 @@ public ExpressionTransformer(TableConfig tableConfig,
Schema schema) {
}
}
- // Sort the transform functions based on dependencies
- Set<String> visited = new HashSet<>();
+ // Carry out DFS traversal to topologically sort column names based on
transform function dependencies. Throw
+ // exception if a cycle is discovered. When a name is first seen it is
added to discoveredNames set. When a name
+ // is completely processed (i.e the name and all of its dependencies have
been fully explored and no cycles have
+ // been seen), it gets added to the _expressionEvaluators list in
topologically sorted order. Fully explored
+ // names are removed from discoveredNames set.
+ Set<String> discoveredNames = new HashSet<>();
for (Map.Entry<String, FunctionEvaluator> entry :
expressionEvaluators.entrySet()) {
- topologicalSort(entry.getKey(), expressionEvaluators, visited);
+ String columnName = entry.getKey();
+ if (!_expressionEvaluators.containsKey(columnName)) {
+ topologicalSort(columnName, expressionEvaluators, discoveredNames);
+ }
}
}
private void topologicalSort(String column, Map<String, FunctionEvaluator>
expressionEvaluators,
- Set<String> visited) {
- if (visited.contains(column)) {
- return;
+ Set<String> discoveredNames) {
+ if (discoveredNames.contains(column)) {
Review comment:
You can instead check if (!discoveredNames.add(column)) on line 95 to
void checking set membership twice.
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