Avoid double-counting Automaton in CompiledAutomaton.ramBytesUsed

[reugn]

Description

CompiledAutomaton.ramBytesUsed() counts the underlying Automaton twice on the DFA path, over-reporting retained heap by 18–35% on non-trivial wildcard and regexp queries.

The automaton field is aliased to runAutomaton.automaton — a single Automaton instance referenced from two places:

// CompiledAutomaton.java:261-263
runAutomaton = new ByteRunAutomaton(binary, true);
this.automaton = runAutomaton.automaton;   // same reference

ramBytesUsed() accounts for it twice: once directly via sizeOfObject(automaton), and again through sizeOfObject(runAutomaton) which delegates to RunAutomaton.ramBytesUsed() and adds sizeOfObject(automaton) itself.

The fix is to drop the redundant sizeOfObject(automaton) from CompiledAutomaton.ramBytesUsed(). In the NFA branch both fields are null, so this is a no-op there.

import org.apache.lucene.index.Term;
import org.apache.lucene.search.WildcardQuery;
import org.apache.lucene.util.automaton.*;

Automaton dfa = Operations.determinize(
    WildcardQuery.toAutomaton(new Term("f", "*" + "x".repeat(3000) + "*")),
    Integer.MAX_VALUE);
CompiledAutomaton ca = new CompiledAutomaton(dfa, false, true, false);

System.out.println(ca.ramBytesUsed());
// Before: 8_361_506   (over-reports by 2.15 MB, ratio ~1.35)
// After:  6_214_953   (matches retained heap within 159 bytes)

Cross-checked against org.openjdk.jol.info.GraphLayout.parseInstance(ca).totalSize() — reported below is CompiledAutomaton.ramBytesUsed(), retained is JOL's GraphLayout.totalSize().

Pattern	reported (before)	reported (after)	retained
*foo*	13,634	10,593	10,752
*foo*bar*baz*	53,586	42,921	43,080
*a*b*c*d*e*f*g*	79,282	61,577	61,736
* + x×1000 + *	2,789,994	2,073,945	2,074,104
* + x×3000 + *	8,361,506	6,214,953	6,215,112
*a*b*…*j* (depth 10)	154,522	121,457	121,616
*a*b*…*t* (depth 20)	677,562	548,497	548,656
.*foo.*bar.*	34,258	27,161	27,320

After the fix, ramBytesUsed() lands within a fixed +159-byte offset of actual retained heap across all cases.

[github-actions]

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[javanna]

LGTM

[javanna]

Thanks @reugn !