gianm commented on a change in pull request #9181: Speed up String first/last
aggregators when folding isn't needed.
URL: https://github.com/apache/druid/pull/9181#discussion_r367656434
##########
File path:
processing/src/main/java/org/apache/druid/query/aggregation/first/StringFirstLastUtils.java
##########
@@ -33,23 +36,63 @@
{
private static final int NULL_VALUE = -1;
+ /**
+ * Shorten "s" to "maxBytes" chars. Fast and loose because these are *chars*
not *bytes*. Use
+ * {@link #chop(String, int)} for slower, but accurate chopping.
+ */
+ @Nullable
+ public static String fastLooseChop(@Nullable final String s, final int
maxBytes)
+ {
+ if (s == null || s.length() <= maxBytes) {
+ return s;
+ } else {
+ return s.substring(0, maxBytes);
+ }
+ }
+
+ /**
+ * Shorten "s" to what could fit in "maxBytes" bytes as UTF-8.
+ */
@Nullable
public static String chop(@Nullable final String s, final int maxBytes)
{
if (s == null) {
return null;
} else {
- // Shorten firstValue to what could fit in maxBytes as UTF-8.
final byte[] bytes = new byte[maxBytes];
final int len = StringUtils.toUtf8WithLimit(s, ByteBuffer.wrap(bytes));
return new String(bytes, 0, len, StandardCharsets.UTF_8);
}
}
+ /**
+ * Returns whether a given value selector *might* contain
SerializablePairLongString objects.
+ */
+ public static boolean selectorNeedsFoldCheck(
+ final BaseObjectColumnValueSelector<?> valueSelector,
+ @Nullable final ColumnCapabilities valueSelectorCapabilities
+ )
+ {
+ if (valueSelectorCapabilities != null &&
valueSelectorCapabilities.getType() != ValueType.COMPLEX) {
+ // Known, non-complex type.
+ return false;
+ }
+
+ if (valueSelector instanceof NilColumnValueSelector) {
+ // Nil column, definitely no SerializablePairLongStrings.
+ return false;
+ }
+
+ // Check if the reported class could possibly be
SerializablePairLongString.
+ final Class<?> clazz = valueSelector.classOfObject();
+ return clazz.isAssignableFrom(SerializablePairLongString.class)
Review comment:
I changed it to:
```java
// Check if the selector class could possibly be a
SerializablePairLongString (either a superclass or subclass).
```
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