feat: DH-23013: Keep query compiler output in memory rather than on disk

docs/groovy/conceptual/execution-context.md

@@ -235,7 +235,7 @@ executionContext = ExecutionContext.newBuilder()
     .newQueryScope()
     .setOperationInitializer(OperationInitializer.NON_PARALLELIZABLE)
     .setUpdateGraph(PeriodicUpdateGraph.newBuilder("MyCustomGraph").build())
-    .setQueryCompiler(QueryCompilerImpl.create(Files.createTempDirectory("qc_").toFile(), ClassLoader.getSystemClassLoader()))
+    .setQueryCompiler(QueryCompilerImpl.create())
     .build()
 ```
 
@@ -248,7 +248,7 @@ This approach allows you to specify:
 - **Query scope**: A new, empty query scope via `newQueryScope`.
 - **Operation initializer**: Parallelization behavior of operations.
 - **Update graph**: A custom update graph (e.g., `PeriodicUpdateGraph` or `EventDrivenUpdateGraph`).
-- **Query compiler**: A compiler instance with a specified working directory and class loader.
+- **Query compiler**: A compiler instance with an optional directory to load classes from and classloader.
 
 For use cases requiring event-driven updates instead of periodic updates, you can substitute an `EventDrivenUpdateGraph`:
 
@@ -262,7 +262,7 @@ executionContext = ExecutionContext.newBuilder()
     .newQueryScope()
     .setOperationInitializer(OperationInitializer.NON_PARALLELIZABLE)
     .setUpdateGraph(eventDrivenGraph)
-    .setQueryCompiler(QueryCompilerImpl.create(Files.createTempDirectory("qc_").toFile(), ClassLoader.getSystemClassLoader()))
+    .setQueryCompiler(QueryCompilerImpl.create())
     .build()
 ```
 

docs/python/conceptual/execution-context.md

@@ -260,12 +260,7 @@ execution_context = (
     .newQueryScope()
     .setOperationInitializer(OperationInitializer.NON_PARALLELIZABLE)
     .setUpdateGraph(PeriodicUpdateGraph.newBuilder("MyCustomGraph").build())
-    .setQueryCompiler(
-        QueryCompilerImpl.create(
-            jpy.get_type("java.io.File")(temp_dir),
-            jpy.get_type("java.lang.ClassLoader").getSystemClassLoader(),
-        )
-    )
+    .setQueryCompiler(QueryCompilerImpl.create())
     .build()
 )
 ```
@@ -279,7 +274,7 @@ This approach allows you to specify:
 - **Query scope**: A new, empty query scope via `newQueryScope`.
 - **Operation initializer**: Parallelization behavior of operations.
 - **Update graph**: A custom update graph (e.g., `PeriodicUpdateGraph` or `EventDrivenUpdateGraph`).
-- **Query compiler**: A compiler instance with a specified working directory and class loader.
+- **Query compiler**: A custom query compiler, which can be created with an optional class directory, plus optional classloader
 
 For use cases requiring event-driven updates instead of periodic updates, you can substitute an `EventDrivenUpdateGraph`:
 
@@ -306,12 +301,7 @@ execution_context = (
     .newQueryScope()
     .setOperationInitializer(OperationInitializer.NON_PARALLELIZABLE)
     .setUpdateGraph(event_driven_graph)
-    .setQueryCompiler(
-        QueryCompilerImpl.create(
-            jpy.get_type("java.io.File")(temp_dir),
-            jpy.get_type("java.lang.ClassLoader").getSystemClassLoader(),
-        )
-    )
+    .setQueryCompiler(QueryCompilerImpl.create())
     .build()
 )
 ```

engine/context/src/main/java/io/deephaven/engine/context/QueryCompiler.java

@@ -10,6 +10,16 @@
 
 import java.util.concurrent.ExecutionException;
 
+/**
+ * Java compiler api, specifically geared towards query language expressions. Implementations should be constructed with
+ * a path on disk to existing bytecode to use in addition to {@code java.class.path}. Likewise, callers must ensure that
+ * the context classloader already contains those input classes - the new class will be loaded in a child classloader to
+ * ensure that the class can be GCd when neither it nor the compiler instance are reachable.
+ * <p>
+ * Requests for compilation will never depend on other classes compiled by this or any other QueryCompiler, and are
+ * expected to be unique based on the provided class name. This enables the implementation to cache classes and only
+ * compile and load a class once per name.
+ */
 public interface QueryCompiler {
 
     /**

engine/context/src/test/java/io/deephaven/engine/context/TestQueryCompiler.java

@@ -14,9 +14,7 @@
 import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
-import org.junit.rules.TemporaryFolder;
 
-import java.io.IOException;
 import java.lang.reflect.Method;
 import java.time.Instant;
 import java.time.LocalDateTime;
@@ -60,18 +58,14 @@ private static String generateClassBody(final String className) {
     @Rule
     public final EngineCleanup framework = new EngineCleanup();
 
-    @Rule
-    public TemporaryFolder folder = new TemporaryFolder();
-
     private SafeCloseable executionContextClosable;
 
     @Before
-    public void setUp() throws IOException {
+    public void setUp() {
         executionContextClosable = ExecutionContext.newBuilder()
                 .captureQueryLibrary()
                 .captureQueryScope()
-                .setQueryCompiler(QueryCompilerImpl.create(
-                        folder.newFolder(), TestQueryCompiler.class.getClassLoader()))
+                .setQueryCompiler(QueryCompilerImpl.create())
                 .build()
                 .open();
     }
@@ -375,12 +369,15 @@ public void testBadCompile() {
                         CompletionStageFuture.make(),
                 };
 
-        final QueryCompilerImpl badCompiler = QueryCompilerImpl.createForUnitTests(List.of("InvalidClassArgument"));
+        final QueryCompilerImpl badCompiler = QueryCompilerImpl.create();
+        badCompiler.setClassNamesForAnnotationProcessing(List.of("InvalidClassArgument"));
+
         UncheckedDeephavenException e = org.junit.Assert.assertThrows(UncheckedDeephavenException.class,
                 () -> badCompiler.compile(requests, resolvers));
         org.junit.Assert.assertEquals("Error Invoking Compiler, no source present in diagnostic:\n" +
                 "Class names, 'InvalidClassArgument', are only accepted if annotation processing is explicitly requested",
                 e.getMessage());
+
     }
 
     @Test