BloomFilterMightContain Predicate Expression

Author: jaceklaskowski

docs/expressions/BloomFilterMightContain.md

@@ -1,14 +1,83 @@
-# BloomFilterMightContain Expression
+---
+title: BloomFilterMightContain
+---
+
+# BloomFilterMightContain Predicate Expression
+
+`BloomFilterMightContain` is a [Predicate](Predicate.md) that uses [BloomFilter](#bloomFilter) when executed ([evaluate](#eval) and [doGenCode](#doGenCode)) to [mightContainLong](../bloom-filter-join/BloomFilter.md#mightContainLong).
 
 `BloomFilterMightContain` is a [BinaryExpression](Expression.md#BinaryExpression).
 
+??? note "`null` Result"
+    `BloomFilterMightContain` returns `null` when executed and there is neither [BloomFilter](#bloomFilter) nor [value](#valueExpression) (for an [InternalRow](../InternalRow.md)) defined.
+
 ## Creating Instance
 
 `BloomFilterMightContain` takes the following to be created:
 
-* <span id="bloomFilterExpression"> Bloom Filter [Expression](Expression.md)
-* <span id="valueExpression"> Value [Expression](Expression.md)
+* [Bloom Filter Expression](#bloomFilterExpression)
+* [Value Expression](#valueExpression)
 
 `BloomFilterMightContain` is created when:
 
 * [InjectRuntimeFilter](../logical-optimizations/InjectRuntimeFilter.md) logical optimization is executed (and [injects a BloomFilter](../logical-optimizations/InjectRuntimeFilter.md#injectBloomFilter))
+
+### Bloom Filter Expression { #bloomFilterExpression }
+
+`BloomFilterMightContain` is given a Bloom Filter [Expression](Expression.md) when [created](#creating-instance).
+
+The Bloom Filter expression is always a [ScalarSubquery](ScalarSubquery.md) expression over an [Aggregate](../logical-operators/Aggregate.md) logical operator.
+
+The `Aggregate` logical operator is created as follows:
+
+* No grouping (all rows are in the same group)
+* [BloomFilterAggregate](BloomFilterAggregate.md) as the aggregate function (with `XxHash64` child expression)
+
+### Value Expression { #valueExpression }
+
+`BloomFilterMightContain` is given a Value [Expression](Expression.md) when [created](#creating-instance).
+
+The Value expression is always an `XxHash64` expression (of type `Long`).
+
+!!! note "`null` Value"
+    If the value evaluates to `null`, `BloomFilterMightContain` evaluates to `null` (in [eval](#eval) and [doGenCode](#doGenCode)).
+
+## BloomFilter { #bloomFilter }
+
+```scala
+bloomFilter: BloomFilter
+```
+
+??? note "Lazy Value"
+    `bloomFilter` is a Scala **lazy value** to guarantee that the code to initialize it is executed once only (when accessed for the first time) and the computed value never changes afterwards.
+
+    Learn more in the [Scala Language Specification]({{ scala.spec }}/05-classes-and-objects.html#lazy).
+
+`bloomFilter` requests the [Bloom Filter Expression](#bloomFilterExpression) to [evaluate](Expression.md#eval) (that gives an `Array[Byte]`).
+
+In the end, `bloomFilter` [deserializes](#deserialize) the bytes (to re-create a [BloomFilter](../bloom-filter-join/BloomFilter.md)).
+
+!!! note
+    If the `Array[Byte]` is `null` (undefined), `bloomFilter` is `null`.
+
+---
+
+`bloomFilter` is used when:
+
+* `BloomFilterMightContain` is requested to [evaluate](#eval) and [doGenCode](#doGenCode)
+
+## Pretty Name { #prettyName }
+
+??? note "Expression"
+
+    ```scala
+    prettyName: String
+    ```
+
+    `prettyName` is part of the [Expression](Expression.md#prettyName) abstraction.
+
+`prettyName` is the following text:
+
+```text
+might_contain
+```