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[SPARK-48748][SQL] Cache numChars in UTF8String #47142

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[SPARK-48748][SQL] Cache numChars in UTF8String #47142

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6f85f1f
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uros-db Jun 28, 2024
9fd254b
Use -1 initially
uros-db Jun 28, 2024
913b79a
Use volatile
uros-db Jun 28, 2024
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11 changes: 11 additions & 0 deletions common/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java
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Original file line number Diff line number Diff line change
Expand Up @@ -58,6 +58,7 @@ public final class UTF8String implements Comparable<UTF8String>, Externalizable,
private Object base;
private long offset;
private int numBytes;
private volatile int numChars = -1;

public Object getBaseObject() { return base; }
public long getBaseOffset() { return offset; }
Expand Down Expand Up @@ -253,6 +254,16 @@ public int numBytes() {
* Returns the number of code points in it.
*/
public int numChars() {
if (numChars == -1) numChars = getNumChars();
return numChars;
}

/**
* Private helper method to calculate the number of code points in the UTF-8 string. Counting
* the code points is a linear time operation, as we need to scan the entire UTF-8 string.
* Hence, this method should generally only be called once for non-empty UTF-8 strings.
*/
private int getNumChars() {
int len = 0;
for (int i = 0; i < numBytes; i += numBytesForFirstByte(getByte(i))) {
len += 1;
Expand Down