felixcheung commented on a change in pull request #24709: [SPARK-27841][SQL]
Improve UTF8String to/fromString()/numBytesForFirstByte() performance
URL: https://github.com/apache/spark/pull/24709#discussion_r288388247
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File path:
common/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java
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@@ -1217,6 +1264,20 @@ public boolean toByte(IntWrapper intWrapper) {
@Override
public String toString() {
+ byte[] bytes = getBytes();
+ // Optimization for ASCII characters: use deprecated string API which
+ // skips charset encoder and simply casts each byte into a char.
+ if (isAscii(bytes)) {
+ return new String(bytes, 0);
Review comment:
it does have to check all bytes though? isn't this grow linearly to the
length of bytes?
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