Applied!!
Erik
On May 3, 2005, at 1:31 PM, Wolfgang Hoschek wrote:
Here's a performance patch for MemoryIndex.MemoryIndexReader that caches the norms for a given field, avoiding repeated recomputation of the norms. Recall that, depending on the query, norms() can be called over and over again with mostly the same parameters. Thus, replace public byte[] norms(String fieldName) with the following code:
/** performance hack: cache norms to avoid repeated expensive calculations */
private byte[] cachedNorms;
private String cachedFieldName;
private Similarity cachedSimilarity;
public byte[] norms(String fieldName) {
byte[] norms = cachedNorms;
Similarity sim = getSimilarity();
if (fieldName != cachedFieldName || sim != cachedSimilarity) { // not cached?
Info info = getInfo(fieldName);
int numTokens = info != null ? info.numTokens : 0;
float n = sim.lengthNorm(fieldName, numTokens);
byte norm = Similarity.encodeNorm(n);
norms = new byte[] {norm};
cachedNorms = norms;
cachedFieldName = fieldName;
cachedSimilarity = sim;
if (DEBUG) System.err.println ("MemoryIndexReader.norms: " + fieldName + ":" + n + ":" + norm + ":" + numTokens);
}
return norms;
}
The effect can be substantial when measured with the profiler, so it's worth it.
Wolfgang.
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