Avoid double-counting Automaton in CompiledAutomaton.ramBytesUsed (#16046)

Author: reugn

lucene/CHANGES.txt

@@ -498,6 +498,8 @@ Bug Fixes
 
 * GITHUB#15878: Fix LargeNumHitsTopDocsCollector not handling requested hit count correctly (Binlong Gao)
 
+* GITHUB#16046: Fix double-counting of underlying Automaton in CompiledAutomaton#ramBytesUsed. (Eugene Rizhkov)
+
 Other
 ---------------------
 * GITHUB#15586: Document that scoring and ranking may change across major Lucene versions, and that applications requiring stable ranking should explicitly configure Similarity. (Parveen Saini)

lucene/core/src/java/org/apache/lucene/util/automaton/CompiledAutomaton.java

@@ -535,8 +535,8 @@ public boolean equals(Object obj) {
 
   @Override
   public long ramBytesUsed() {
+    // this.automaton is accounted via runAutomaton.ramBytesUsed()
     return BASE_RAM_BYTES
-        + RamUsageEstimator.sizeOfObject(automaton)
         + RamUsageEstimator.sizeOfObject(commonSuffixRef)
         + RamUsageEstimator.sizeOfObject(runAutomaton)
         + RamUsageEstimator.sizeOfObject(nfaRunAutomaton)

lucene/core/src/test/org/apache/lucene/util/automaton/TestCompiledAutomaton.java

@@ -28,6 +28,7 @@
 import org.apache.lucene.search.QueryVisitor;
 import org.apache.lucene.search.TermQuery;
 import org.apache.lucene.tests.util.LuceneTestCase;
+import org.apache.lucene.tests.util.RamUsageTester;
 import org.apache.lucene.tests.util.TestUtil;
 import org.apache.lucene.util.BytesRef;
 import org.apache.lucene.util.BytesRefBuilder;
@@ -256,6 +257,18 @@ public void consumeTermsMatching(
     assertTrue(matchingCalled[0]);
   }
 
+  public void testRamBytesUsed() {
+    Automaton a =
+        Operations.determinize(new RegExp(".*foo.*bar.*baz.*").toAutomaton(), Integer.MAX_VALUE);
+    CompiledAutomaton ca = new CompiledAutomaton(a, false, true, false);
+    assertEquals(CompiledAutomaton.AUTOMATON_TYPE.NORMAL, ca.type);
+    assertNotNull(ca.runAutomaton);
+
+    long reported = ca.ramBytesUsed();
+    long actual = RamUsageTester.ramUsed(ca);
+    assertEquals((double) actual, (double) reported, (double) actual * 0.10);
+  }
+
   private static Automaton makeSimpleNfa(char ch) {
     return makeDeterministicNormalAutomaton(ch, ch);
   }