Github user chunhui-shi commented on a diff in the pull request:
https://github.com/apache/drill/pull/430#discussion_r56924863
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/HashHelper.java
---
@@ -17,47 +17,77 @@
*/
package org.apache.drill.exec.expr.fn.impl;
+import io.netty.buffer.DrillBuf;
+import org.apache.drill.common.config.DrillConfig;
+import org.apache.drill.common.exceptions.DrillConfigurationException;
+
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
-public class HashHelper {
+public abstract class HashHelper {
static final org.slf4j.Logger logger =
org.slf4j.LoggerFactory.getLogger(HashHelper.class);
+ public static final String defaultHashClassName = new
String("org.apache.drill.exec.expr.fn.impl.MurmurHash3");
+ static final String HASH_CLASS_PROP = "drill.exec.hash.class";
+ static String actualHashClassName = defaultHashClassName;
+ static DrillHash hashCall = new MurmurHash3();
+ static {
- /** taken from mahout **/
- public static int hash(ByteBuffer buf, int seed) {
- // save byte order for later restoration
-
- int m = 0x5bd1e995;
- int r = 24;
+ try {
+ DrillConfig config = DrillConfig.create();
+ String configuredClassName = config.getString(HASH_CLASS_PROP);
+ if(configuredClassName != null && configuredClassName != "") {
+ actualHashClassName = configuredClassName;
+ hashCall = config.getInstanceOf(HASH_CLASS_PROP, DrillHash.class);
+ }
+ logger.debug("HashHelper initializes with " + actualHashClassName);
+ }
+ catch(Exception ex){
+ logger.error("Could not initialize Hash %s", ex.getMessage());
+ }
+ }
- int h = seed ^ buf.remaining();
+ public static String getHashClassName(){
+ return actualHashClassName;
+ }
- while (buf.remaining() >= 4) {
- int k = buf.getInt();
+ public static int hash32(int val, long seed) {
+ double converted = val;
+ return hash32(converted, seed);
+ }
+ public static int hash32(long val, long seed) {
+ double converted = val;
+ return hash32(converted, seed);
+ }
+ public static int hash32(float val, long seed){
+ double converted = val;
+ return hash32(converted, seed);
+ }
- k *= m;
- k ^= k >>> r;
- k *= m;
+ public static int hash32(double val, long seed){
+ return hashCall.hash32(val, seed);
+ }
- h *= m;
- h ^= k;
- }
+ public static int hash32(int start, int end, DrillBuf buffer, int seed){
+ return hashCall.hash32(start, end, buffer, seed);
--- End diff --
@jacques-n Do you think this indirection may cause some performance
overhead? The indirection was introduced to allow us to test different hash
functions without rebuilding the whole thing.
As to the second ask, can you elaborate "this class dereference to the
hashCall class field gets eliminated" for me to understand the concern here?
Thanks.
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