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https://issues.apache.org/jira/browse/DRILL-5052?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15734274#comment-15734274
]
ASF GitHub Bot commented on DRILL-5052:
---------------------------------------
Github user paul-rogers commented on a diff in the pull request:
https://github.com/apache/drill/pull/660#discussion_r91632286
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/compile/CachedClassLoader.java
---
@@ -0,0 +1,70 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.drill.exec.compile;
+
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.util.Map;
+import java.util.concurrent.ConcurrentMap;
+
+import com.google.common.collect.MapMaker;
+
+/**
+ * Class loader for "plain-old Java" generated classes.
+ * Very basic implementation: allows defining a class from
+ * byte codes and finding the loaded classes. Delegates
+ * all other class requests to the thread context class
+ * loader. This structure ensures that a generated class can
+ * find both its own inner classes as well as all the standard
+ * Drill implementation classes.
+ */
+
+public class CachedClassLoader extends URLClassLoader {
+
+ /**
+ * Cache of generated classes. Semantics: a single thread defines
+ * the classes, many threads may access the classes.
+ */
+
+ private ConcurrentMap<String, Class<?>> cache = new
MapMaker().concurrencyLevel(4).makeMap();
+
+ public CachedClassLoader( ) {
+ super(new URL[0], Thread.currentThread().getContextClassLoader());
+ }
+
+ public void addClass( String fqcn, byte[] byteCodes ) {
+
+ assert ! cache.containsKey( fqcn );
+ Class<?> newClass = defineClass(fqcn, byteCodes, 0, byteCodes.length);
+ cache.put( fqcn, newClass );
+ }
+
+ @Override
+ public Class<?> findClass(String className) throws
ClassNotFoundException {
+ Class<?> theClass = cache.get( className );
+ if ( theClass != null ) {
+ return theClass; }
+ return super.findClass(className);
+ }
+
+ public void addClasses(Map<String, byte[]> results) {
+ for ( String key : results.keySet() ) {
+ addClass( key, results.get( key ) );
+ }
--- End diff --
Done.
> Option to debug generated Java code using an IDE
> ------------------------------------------------
>
> Key: DRILL-5052
> URL: https://issues.apache.org/jira/browse/DRILL-5052
> Project: Apache Drill
> Issue Type: Improvement
> Components: Execution - Codegen
> Affects Versions: 1.8.0
> Reporter: Paul Rogers
> Assignee: Paul Rogers
> Priority: Minor
>
> Drill makes extensive use of Java code generation to implement its operators.
> Drill uses sophisticated techniques to blend generated code with pre-compiled
> template code. An unfortunate side-effect of this behavior is that it is very
> difficult to visualize and debug the generated code.
> As it turns out, Drill's code-merge facility is, in essence, a do-it-yourself
> version of subclassing. The Drill "template" is the parent class, the
> generated code is the subclass. But, rather than using plain-old subclassing,
> Drill combines the code from the two classes into a single "artificial"
> packet of byte codes for which no source exists.
> Modify the code generation path to optionally allow "plain-old Java"
> compilation: the generated code is a subclass of the template. Compile the
> generated code as a plain-old Java class with no byte-code fix-up. Write the
> code to a known location that the IDE can search when looking for source
> files.
> With this change, developers can turn on the above feature, set a breakpoint
> in a template, then step directly into the generated Java code called from
> the template.
> This feature should be an option, enabled by developers when needed. The
> existing byte-code technique should be used for production code generation.
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