[GitHub] [flink] lsyldliu commented on a diff in pull request #20243: [FLINK-28491][table-planner] Introduce APPROX_COUNT_DISTINCT aggregate function for batch sql

[GitBox <gi...@apache.org>]

lsyldliu commented on code in PR #20243:
URL: https://github.com/apache/flink/pull/20243#discussion_r921862422


##########
flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/functions/aggregate/hyperloglog/XxHash64Function.java:
##########
@@ -0,0 +1,100 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.table.runtime.functions.aggregate.hyperloglog;
+
+import org.apache.flink.core.memory.MemorySegment;
+import org.apache.flink.core.memory.MemorySegmentFactory;
+import org.apache.flink.table.api.TableException;
+import org.apache.flink.table.data.DecimalData;
+import org.apache.flink.table.data.binary.BinaryStringData;
+
+import java.math.BigDecimal;
+import java.sql.Date;
+import java.sql.Time;
+import java.sql.Timestamp;
+
+/** Utility class to get hash code based on {@link XXH64}. */
+public class XxHash64Function {
+
+    public static final long DEFAULT_SEED = 42L;
+
+    public static long hashInt(int i, long seed) {
+        return XXH64.hashInt(i, seed);
+    }
+
+    public static long hashLong(long l, long seed) {
+        return XXH64.hashLong(l, seed);
+    }
+
+    public static long hashUnsafeBytes(MemorySegment base, int offset, int length, long seed) {
+        return XXH64.hashUnsafeBytes(base, offset, length, seed);
+    }
+
+    /**
+     * Computes hash of a given `value`. The caller needs to check the validity of input `value`.
+     */
+    public static long hash(Object value, long seed) {
+        if (value == null) {
+            return seed;
+        } else if (value instanceof Boolean) {
+            boolean b = (boolean) value;
+            return hashInt(b ? 1 : 0, seed);
+        } else if (value instanceof Byte) {
+            return hashInt((Byte) value, seed);
+        } else if (value instanceof Short) {
+            return hashInt((Short) value, seed);
+        } else if (value instanceof Integer) {
+            return hashInt((Integer) value, seed);
+        } else if (value instanceof Long) {
+            return hashLong((Long) value, seed);
+        } else if (value instanceof Float) {
+            return hashInt(Float.floatToIntBits((Float) value), seed);
+        } else if (value instanceof Double) {
+            return hashLong(Double.doubleToLongBits((Double) value), seed);
+        } else if (value instanceof Date) {
+            return hashLong(((Date) value).getTime(), seed);
+        } else if (value instanceof Time) {
+            return hashLong(((Time) value).getTime(), seed);
+        } else if (value instanceof Timestamp) {
+            return hashLong(((Timestamp) value).getTime(), seed);
+        } else if (value instanceof BigDecimal) {

Review Comment:
   I'm not understand why here ignore `DecimalData` branch?



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