Github user paul-rogers commented on a diff in the pull request:
https://github.com/apache/drill/pull/574#discussion_r77697563
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/DrillFunctionRegistry.java
---
@@ -218,4 +302,141 @@ private void
registerOperatorsWithoutInference(DrillOperatorTable operatorTable)
}
}
}
+
+ /**
+ * Function registry holder. Stores function implementations by jar
name, function name.
+ */
+ private class GenericRegistryHolder<T, U> {
+ private final ReadWriteLock readWriteLock = new
ReentrantReadWriteLock();
+ private final AutoCloseableLock readLock = new
AutoCloseableLock(readWriteLock.readLock());
+ private final AutoCloseableLock writeLock = new
AutoCloseableLock(readWriteLock.writeLock());
+
+ // jar name, Map<function name, List<signature>
+ private final Map<T, Map<T, List<T>>> jars;
+
+ // function name, Map<signature, function holder>
+ private final Map<T, Map<T, U>> functions;
+
+ public GenericRegistryHolder() {
+ this.functions = Maps.newHashMap();
+ this.jars = Maps.newHashMap();
+ }
+
+ public void addJar(T jName, Map<T, Pair<T, U>> sNameMap) {
+ try (AutoCloseableLock lock = writeLock.open()) {
+ Map<T, List<T>> map = jars.get(jName);
+ if (map != null) {
+ removeAllByJar(jName);
+ }
+ map = Maps.newHashMap();
+ jars.put(jName, map);
+
+ for (Entry<T, Pair<T, U>> entry : sNameMap.entrySet()) {
+ T sName = entry.getKey();
+ Pair<T, U> pair = entry.getValue();
+ addFunction(jName, pair.getKey(), sName, pair.getValue());
--- End diff --
Rather expensive. We have the function map right in our hands. Yet, on
every add function, we look it up again.
Perhaps the code would be simpler if we declared intermediate classes such
as one that is the method registry for a function, rather than using generic
classes. That way, your method registry class could do the work to register
methods concisely rather than trying to do it generically as here.
Also, having smaller classes makes unit testing easier. (This class is unit
tested, right? Actually, it can't be: the class is private so not reachable
from a unit test...) This raises a question: how will we test the detailed
logic here if we don't have unit tests? Using system level tests that send SQL
to Drill?
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