[GitHub] [lucene-solr] pawel-bugalski-dynatrace commented on pull request #2429: LUCENE-9791 Allow calling BytesRefHash#find concurrently

[GitBox <gi...@apache.org>]

pawel-bugalski-dynatrace commented on pull request #2429:
URL: https://github.com/apache/lucene-solr/pull/2429#issuecomment-785282649


   > The problem is this change doesn't just impact find() like the description states, but also other things like add() getting called by TermsHashPerField, a hot spot of indexer. I don't think we should rely on oracle's C2 EA to not create monster amounts of garbage, this is too important of a spot.
   
   In that case we can easily implement `equals` without allocation.
   ```
   private boolean equals(int id, BytesRef b) {
     final int textStart = bytesStart[id];
     final byte[] bytes = pool.buffers[textStart >> BYTE_BLOCK_SHIFT];
     int pos = textStart & BYTE_BLOCK_MASK;
     final int length;
     final int offset;
     if ((bytes[pos] & 0x80) == 0) {
       // length is 1 byte
       length = bytes[pos];
       offset = pos + 1;
     } else {
       // length is 2 bytes
       length = (bytes[pos] & 0x7f) + ((bytes[pos + 1] & 0xff) << 7);
       offset = pos + 2;
     }
     return Arrays.equals(
         bytes,
         offset,
         offset + length,
         b.bytes,
         b.offset,
         b.offset + b.length);
   } 
   ```


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