msokolov commented on issue #14886:
URL: https://github.com/apache/lucene/issues/14886#issuecomment-3045670761
sure -- this is what we are using; you can see it devolves to hashing
`toString()` in cases that aren't covered explicitly, so in theory it is fully
general, but `toString()` isn't really reliable for this purpose, I think, so
this is just sort of waving at these other query types.
```
// Query.hashCode is not stable across processes (partly because of
including the Class hash).
static long queryHashCodeStable(Query q) {
long hashCode = 0;
long prime = 31L;
if (q instanceof TermQuery tq) {
// Term hashCode() relies on BytesRef.hashCode() which is not
stable
Term t = tq.getTerm();
hashCode = hashCode * prime + t.field().hashCode();
hashCode = hashCode * prime + t.text().hashCode();
} else if (q instanceof BooleanQuery bq) {
List<BooleanClause> clauses = new ArrayList<>(bq.clauses());
clauses.sort((a, b) -> a.toString().compareTo(b.toString()));
for (BooleanClause clause : clauses) {
hashCode = prime * hashCode + clause.getOccur().ordinal();
hashCode = prime * hashCode +
queryHashCodeStable(clause.getQuery());
}
} else if (q instanceof MatchAllDocsQuery) {
hashCode = 0x1234567890abcdefL;
} else if (q instanceof ExactSortedNumericDocValuesQuery esndvq) {
hashCode = Long.hashCode(esndvq.getValue());
} else {
// eg numeric range queries
hashCode = q.toString().hashCode();
}
// System.out.println("hashCode(" + q + ") = " + hashCode);
return hashCode;
}
```
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