[GitHub] [beam] Imfuyuwei commented on a change in pull request #12079: [BEAM-9890] Support BIT_AND aggregation function in Beam SQL

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Imfuyuwei commented on a change in pull request #12079:
URL: https://github.com/apache/beam/pull/12079#discussion_r445160365



##########
File path: sdks/java/extensions/sql/src/main/java/org/apache/beam/sdk/extensions/sql/impl/transform/BeamBuiltinAggregations.java
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@@ -383,4 +392,30 @@ public Long extractOutput(Long accum) {
       return accum;
     }
   }
+
+  static class BitAnd<T extends Number> extends CombineFn<T, Long, Long> {
+    @Override
+    public Long createAccumulator() {
+      return -1L;

Review comment:
       Because -1L is represented as 64 bits of 1 in binary while 1L only has one 1 at the least significant bit. 
   
   In order to do bit_and operation, I think the initial bit mask should consists of only 1s, so I use -1L.




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