[GitHub] [spark] wangyum commented on a diff in pull request #37697: [SPARK-40248][SQL] Use larger number of bits to build Bloom filter

[GitBox]

wangyum commented on code in PR #37697:
URL: https://github.com/apache/spark/pull/37697#discussion_r960736515


##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/BloomFilterAggregate.scala:
##########
@@ -55,6 +55,13 @@ case class BloomFilterAggregate(
       Multiply(estimatedNumItemsExpression, Literal(8L)))
   }
 
+  def this(child: Expression, estimatedNumItems: Long) = {
+    this(child, Literal(estimatedNumItems),
+      Literal(math.min(
+        BloomFilter.optimalNumOfBits(estimatedNumItems, estimatedNumItems / 
3000000000L.toDouble),
+        SQLConf.get.getConf(SQLConf.RUNTIME_BLOOM_FILTER_MAX_NUM_BITS))))
+  }

Review Comment:
   How about?
   ```scala
       this(child, Literal(estimatedNumItems),
         Literal(math.min(
           BloomFilter.optimalNumOfBits(estimatedNumItems,
             estimatedNumItems / 
(SQLConf.get.getConf(SQLConf.RUNTIME_BLOOM_FILTER_MAX_NUM_ITEMS) /
               BloomFilter.DEFAULT_FPP)),
           SQLConf.get.getConf(SQLConf.RUNTIME_BLOOM_FILTER_MAX_NUM_BITS))))
   ```
   The smaller `estimatedNumItems`, the smaller the `FPP`.
   
   
   estimatedNumItems | FPP | numBits
   -- | -- | --
   RUNTIME_BLOOM_FILTER_MAX_NUM_ITEMS | DEFAULT_FPP | 29193763
   2000000 | 0.015 | 17482271
   1000000 | 0.0075 | 10183830
   100000 | 7.50E-04 | 1497636
   10000 | 7.50E-05 | 197688
   1000 | 7.50E-06 | 24561
   100 | 7.50E-07 | 2935
   10 | 7.50E-08 | 341
   
   
   



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