darshanj commented on a change in pull request #11610:
URL: https://github.com/apache/beam/pull/11610#discussion_r425689324



##########
File path: 
sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/SetFns.java
##########
@@ -0,0 +1,618 @@
+/*
+ * 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.beam.sdk.transforms;
+
+import static 
org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkArgument;
+import static 
org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkNotNull;
+
+import java.util.ArrayList;
+import java.util.List;
+import org.apache.beam.sdk.Pipeline;
+import org.apache.beam.sdk.coders.Coder;
+import org.apache.beam.sdk.transforms.join.CoGbkResult;
+import org.apache.beam.sdk.transforms.join.CoGroupByKey;
+import org.apache.beam.sdk.transforms.join.KeyedPCollectionTuple;
+import org.apache.beam.sdk.transforms.windowing.Trigger;
+import org.apache.beam.sdk.transforms.windowing.WindowFn;
+import org.apache.beam.sdk.values.KV;
+import org.apache.beam.sdk.values.PCollection;
+import org.apache.beam.sdk.values.PCollectionList;
+import org.apache.beam.sdk.values.TupleTag;
+import 
org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.Iterables;
+
+public class SetFns {
+
+  /**
+   * Returns a new {@code PTransform} transform that follows SET DISTINCT 
semantics to compute the
+   * intersection with provided {@code PCollection<T>}.
+   *
+   * <p>The argument should not be modified after this is called.
+   *
+   * <p>The elements of the output {@link PCollection} will all distinct 
elements that present in
+   * both pipeline is constructed and provided {@link PCollection}.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of {@code PCollection<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   *
+   * PCollection<String> left = p.apply(Create.of("1", "2", "3", "3","4", 
"5"));
+   * PCollection<String> right = p.apply(Create.of("1", "3", "4","4", "6"));
+   *
+   * PCollection<String> results =
+   *     left.apply(SetFns.intersectDistinct(right)); // results will be 
PCollection<String> containing: "1","3","4"
+   *
+   * }</pre>
+   *
+   * @param <T> the type of the elements in the input and output {@code 
PCollection<T>}s.
+   */
+  public static <T> SetImpl<T> intersectDistinct(PCollection<T> 
rightCollection) {
+    checkNotNull(rightCollection, "rightCollection argument is null");
+    return new SetImpl<>(rightCollection, intersectDistinct());
+  }
+
+  /**
+   * Returns a {@code PTransform} that takes a {@code 
PCollectionList<PCollection<T>>} and returns a
+   * {@code PCollection<T>} containing intersection of collections done in 
order for all collections
+   * in {@code PCollectionList<T>}.
+   *
+   * <p>Returns a new {@code PTransform} transform that follows SET DISTINCT 
semantics which takes a
+   * {@code PCollectionList<PCollection<T>>} and returns a {@code 
PCollection<T>} containing
+   * intersection of collections done in order for all collections in {@code 
PCollectionList<T>}.
+   *
+   * <p>The elements of the output {@link PCollection} will have all distinct 
elements that are
+   * present in both pipeline is constructed and next {@link PCollection} in 
the list and applied to
+   * all collections in order.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of first in {@code PCollectionList<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   *
+   * PCollection<String> first = p.apply(Create.of("1", "2", "3", "3","4", 
"5"));
+   * PCollection<String> second = p.apply(Create.of("1", "3", "4","4", "6"));
+   * PCollection<String> third = p.apply(Create.of("3", "4","4"));
+   *
+   * // Following example will perform (first intersect second) intersect 
third.
+   * PCollection<String> results =
+   *     PCollectionList.of(first).and(second).and(third)
+   *     .apply(SetFns.intersectDistinct()); // results will be 
PCollection<String> containing: "3","4"
+   *
+   * }</pre>
+   *
+   * @param <T> the type of the elements in the input {@code 
PCollectionList<T>} and output {@code
+   *     PCollection<T>}s.
+   */
+  public static <T> SetImplCollections<T> intersectDistinct() {
+    SerializableBiFunction<Long, Long, Long> intersectFn =
+        (numberOfElementsinLeft, numberOfElementsinRight) ->
+            (numberOfElementsinLeft > 0 && numberOfElementsinRight > 0) ? 1L : 
0L;
+    return new SetImplCollections<>(intersectFn);
+  }
+
+  /**
+   * Returns a new {@code PTransform} transform that follows SET ALL semantics 
to compute the
+   * intersection with provided {@code PCollection<T>}.
+   *
+   * <p>The argument should not be modified after this is called.
+   *
+   * <p>The elements of the output {@link PCollection} which will follow 
INTESECT_ALL Semantics as
+   * follows: Given there are m elements on pipeline which is constructed 
{@link PCollection} (left)
+   * and n elements on in provided {@link PCollection} (right): - it will 
output MIN(m - n, 0)
+   * elements of left for all elements which are present in both left and 
right.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of {@code PCollection<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   *
+   * PCollection<String> left = p.apply(Create.of("1","1","1", "2", "3", 
"3","4", "5"));
+   * PCollection<String> right = p.apply(Create.of("1","1", "3", "4","4", 
"6"));
+   *
+   * PCollection<String> results =
+   *     left.apply(SetFns.intersectAll(right)); // results will be 
PCollection<String> containing: "1","1","3","4"
+   * }</pre>
+   *
+   * @param <T> the type of the elements in the input and output {@code 
PCollection<T>}s.
+   */
+  public static <T> SetImpl<T> intersectAll(PCollection<T> rightCollection) {
+    checkNotNull(rightCollection, "rightCollection argument is null");
+    return new SetImpl<>(rightCollection, intersectAll());
+  }
+
+  /**
+   * Returns a new {@code PTransform} transform that follows SET ALL semantics 
which takes a {@code
+   * PCollectionList<PCollection<T>>} and returns a {@code PCollection<T>} 
containing intersection
+   * all of collections done in order for all collections in {@code 
PCollectionList<T>}.
+   *
+   * <p>The elements of the output {@link PCollection} which will follow 
INTERSECT_ALL semantics.
+   * Output is calculated as follows: Given there are m elements on pipeline 
which is constructed
+   * {@link PCollection} (left) and n elements on in provided {@link 
PCollection} (right): - it will
+   * output MIN(m - n, 0) elements of left for all elements which are present 
in both left and
+   * right.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of first in {@code PCollectionList<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   * PCollection<String> first = p.apply(Create.of("1","1","1", "2", "3", 
"3","4", "5"));
+   * PCollection<String> second = p.apply(Create.of("1","1", "3", "4","4", 
"6"));
+   * PCollection<String> third = p.apply(Create.of("1", "5"));
+   *
+   * // Following example will perform (first intersect second) intersect 
third.
+   * PCollection<String> results =
+   *     PCollectionList.of(first).and(second).and(third)
+   *     .apply(SetFns.intersectAll()); // results will be PCollection<String> 
containing: "1"
+   *
+   * }</pre>
+   *
+   * @param <T> the type of the elements in the input {@code 
PCollectionList<T>} and output {@code
+   *     PCollection<T>}s.
+   */
+  public static <T> SetImplCollections<T> intersectAll() {
+    return new SetImplCollections<>(Math::min);
+  }
+
+  /**
+   * Returns a new {@code PTransform} transform that follows SET DISTINCT 
semantics to compute the
+   * difference (except) with provided {@code PCollection<T>}.
+   *
+   * <p>The argument should not be modified after this is called.
+   *
+   * <p>The elements of the output {@link PCollection} will all distinct 
elements that present in
+   * pipeline is constructed but not present in provided {@link PCollection}.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of {@code PCollection<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   *
+   * PCollection<String> left = p.apply(Create.of("1","1","1", "2", "3", 
"3","4", "5"));
+   * PCollection<String> right = p.apply(Create.of("1","1", "3", "4","4", 
"6"));
+   *
+   * PCollection<String> results =
+   *     left.apply(SetFns.exceptDistinct(right)); // results will be 
PCollection<String> containing: "2","5"
+   * }</pre>
+   *
+   * @param <T> the type of the elements in the input and output {@code 
PCollection<T>}s.
+   */
+  public static <T> SetImpl<T> exceptDistinct(PCollection<T> rightCollection) {
+    checkNotNull(rightCollection, "rightCollection argument is null");
+    return new SetImpl<>(rightCollection, exceptDistinct());
+  }
+
+  /**
+   * Returns a {@code PTransform} that takes a {@code 
PCollectionList<PCollection<T>>} and returns a
+   * {@code PCollection<T>} containing difference (except) of collections done 
in order for all
+   * collections in {@code PCollectionList<T>}.
+   *
+   * <p>Returns a new {@code PTransform} transform that follows SET DISTINCT 
semantics which takes a
+   * {@code PCollectionList<PCollection<T>>} and returns a {@code 
PCollection<T>} containing
+   * difference (except) of collections done in order for all collections in 
{@code
+   * PCollectionList<T>}.
+   *
+   * <p>The elements of the output {@link PCollection} will have all distinct 
elements that are
+   * present in pipeline is constructed but not present in next {@link 
PCollection} in the list and
+   * applied to all collections in order.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of first in {@code PCollectionList<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   * PCollection<String> first = p.apply(Create.of("1","1","1", "2", "3", 
"3","4", "5"));
+   * PCollection<String> second = p.apply(Create.of("1","1", "3", "4","4", 
"6"));
+   *
+   * PCollection<String> third = p.apply(Create.of("1", "2","2"));
+   *
+   * // Following example will perform (first intersect second) intersect 
third.
+   * PCollection<String> results =
+   *     PCollectionList.of(first).and(second).and(third)
+   *     .apply(SetFns.exceptDistinct()); // results will be 
PCollection<String> containing: "5"
+   *
+   * }</pre>
+   *
+   * @param <T> the type of the elements in the input {@code 
PCollectionList<T>} and output {@code
+   *     PCollection<T>}s.
+   */
+  public static <T> SetImplCollections<T> exceptDistinct() {
+    SerializableBiFunction<Long, Long, Long> exceptFn =
+        (numberOfElementsinLeft, numberOfElementsinRight) ->
+            numberOfElementsinLeft > 0 && numberOfElementsinRight == 0 ? 1L : 
0L;
+    return new SetImplCollections<>(exceptFn);
+  }
+
+  /**
+   * Returns a new {@code PTransform} transform that follows SET ALL semantics 
to compute the
+   * difference all (exceptAll) with provided {@code PCollection<T>}.
+   *
+   * <p>The argument should not be modified after this is called.
+   *
+   * <p>The elements of the output {@link PCollection} which will follow 
EXCEPT_ALL Semantics as
+   * follows: Given there are m elements on pipeline which is constructed 
{@link PCollection} (left)
+   * and n elements on in provided {@link PCollection} (right): - it will 
output m elements of left
+   * for all elements which are present in left but not in right. - it will 
output MAX(m - n, 0)
+   * elements of left for all elements which are present in both left and 
right.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of {@code PCollection<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   *
+   * PCollection<String> left = p.apply(Create.of("1","1","1", "2", "3", 
"3","3","4", "5"));
+   * PCollection<String> right = p.apply(Create.of("1", "3", "4","4", "6"));
+   *
+   * PCollection<String> results =
+   *     left.apply(SetFns.exceptAll(right)); // results will be 
PCollection<String> containing: "1","1","2","3","3","5"
+   * }</pre>
+   *
+   * @param <T> the type of the elements in the input and output {@code 
PCollection<T>}s.
+   */
+  public static <T> SetImpl<T> exceptAll(PCollection<T> rightCollection) {
+    checkNotNull(rightCollection, "rightCollection argument is null");
+    return new SetImpl<>(rightCollection, exceptAll());
+  }
+
+  /**
+   * Returns a new {@code PTransform} transform that follows SET ALL semantics 
which takes a {@code
+   * PCollectionList<PCollection<T>>} and returns a {@code PCollection<T>} 
containing difference all
+   * (exceptAll) of collections done in order for all collections in {@code 
PCollectionList<T>}.
+   *
+   * <p>The elements of the output {@link PCollection} which will follow 
EXCEPT_ALL semantics.
+   * Output is calculated as follows: Given there are m elements on pipeline 
which is constructed
+   * {@link PCollection} (left) and n elements on in provided {@link 
PCollection} (right): - it will
+   * output m elements of left for all elements which are present in left but 
not in right. - it
+   * will output MAX(m - n, 0) elements of left for all elements which are 
present in both left and
+   * right.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of first in {@code PCollectionList<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   * PCollection<String> first = p.apply(Create.of("1","1","1", "2", "3", 
"3","3","4", "5"));
+   * PCollection<String> second = p.apply(Create.of("1", "3", "4","4", "6"));
+   * PCollection<String> third = p.apply(Create.of("1", "5"));
+   *
+   * // Following example will perform (first intersect second) intersect 
third.
+   * PCollection<String> results =
+   *     PCollectionList.of(first).and(second).and(third)
+   *     .apply(SetFns.exceptAll()); // results will be PCollection<String> 
containing: "1","2","3","3"
+   *
+   * }</pre>
+   *
+   * @param <T> the type of the elements in the input {@code 
PCollectionList<T>} and output {@code
+   *     PCollection<T>}s.
+   */
+  public static <T> SetImplCollections<T> exceptAll() {
+    SerializableBiFunction<Long, Long, Long> exceptFn =
+        (numberOfElementsinLeft, numberOfElementsinRight) ->
+            Math.max(numberOfElementsinLeft - numberOfElementsinRight, 0L);
+    return new SetImplCollections<>(exceptFn);
+  }
+
+  /**
+   * Returns a new {@code PTransform} transform that follows SET DISTINCT 
semantics to compute the
+   * union with provided {@code PCollection<T>}.
+   *
+   * <p>The argument should not be modified after this is called.
+   *
+   * <p>The elements of the output {@link PCollection} will all distinct 
elements that present in
+   * pipeline is constructed or present in provided {@link PCollection}.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of {@code PCollection<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   *
+   * PCollection<String> left = p.apply(Create.of("1","1","2"));
+   * PCollection<String> right = p.apply(Create.of("1", "3", "4","4"));
+   *
+   * PCollection<String> results =
+   *     left.apply(SetFns.unionDistinct(right)); // results will be 
PCollection<String> containing: "1","2","3","4"
+   * }</pre>
+   *
+   * @param <T> the type of the elements in the input and output {@code 
PCollection<T>}s.
+   */
+  public static <T> SetImpl<T> unionDistinct(PCollection<T> rightCollection) {
+    checkNotNull(rightCollection, "rightCollection argument is null");
+    return new SetImpl<>(rightCollection, unionDistinct());
+  }
+
+  /**
+   * Returns a new {@code PTransform} transform that follows SET DISTINCT 
semantics which takes a
+   * {@code PCollectionList<PCollection<T>>} and returns a {@code 
PCollection<T>} containing union
+   * of collections done in order for all collections in {@code 
PCollectionList<T>}.
+   *
+   * <p>The elements of the output {@link PCollection} will have all distinct 
elements that are
+   * present in pipeline is constructed or present in next {@link PCollection} 
in the list and
+   * applied to all collections in order.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of first in {@code PCollectionList<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   * PCollection<String> first = p.apply(Create.of("1","1","2"));
+   * PCollection<String> second = p.apply(Create.of("1", "3", "4","4"));
+   *
+   * PCollection<String> third = p.apply(Create.of("1", "5"));
+   *
+   * // Following example will perform (first intersect second) intersect 
third.
+   * PCollection<String> results =
+   *     PCollectionList.of(first).and(second).and(third)
+   *     .apply(SetFns.unionDistinct()); // results will be 
PCollection<String> containing: "1","2","3","4","5"
+   *
+   * }</pre>
+   *
+   * @param <T> the type of the elements in the input {@code 
PCollectionList<T>} and output {@code
+   *     PCollection<T>}s.
+   */
+  public static <T> SetImplCollections<T> unionDistinct() {
+    SerializableBiFunction<Long, Long, Long> unionFn =
+        (numberOfElementsinLeft, numberOfElementsinRight) -> 1L;
+    return new SetImplCollections<>(unionFn);
+  }
+
+  /**
+   * Returns a new {@code PTransform} transform that follows SET ALL semantics 
to compute the
+   * unionAll with provided {@code PCollection<T>}.
+   *
+   * <p>The argument should not be modified after this is called.
+   *
+   * <p>The elements of the output {@link PCollection} which will follow 
UNION_ALL semantics as
+   * follows: Given there are m elements on pipeline which is constructed 
{@link PCollection} (left)
+   * and n elements on in provided {@link PCollection} (right): - it will 
output m elements of left
+   * and m elements of right.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of {@code PCollection<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   *
+   * PCollection<String> left = p.apply(Create.of("1","1","2"));
+   * PCollection<String> right = p.apply(Create.of("1", "3", "4","4"));
+   *
+   * PCollection<String> results =
+   *     left.apply(SetFns.unionAll(right)); // results will be 
PCollection<String> containing: "1","1","1","2","3","4","4"
+   * }</pre>
+   *
+   * @param <T> the type of the elements in the input and output {@code 
PCollection<T>}s.
+   */
+  public static <T> SetImpl<T> unionAll(PCollection<T> rightCollection) {
+    checkNotNull(rightCollection, "rightCollection argument is null");
+    return new SetImpl<>(rightCollection, unionAll());
+  }
+
+  /**
+   * Returns a new {@code PTransform} transform that follows SET ALL semantics 
which takes a {@code
+   * PCollectionList<PCollection<T>>} and returns a {@code PCollection<T>} 
containing unionAll of
+   * collections done in order for all collections in {@code 
PCollectionList<T>}.
+   *
+   * <p>The elements of the output {@link PCollection} which will follow 
UNION_ALL semantics. Output
+   * is calculated as follows: Given there are m elements on pipeline which is 
constructed {@link
+   * PCollection} (left) and n elements on in provided {@link PCollection} 
(right): - it will output
+   * m elements of left and m elements of right.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
inputs {@code
+   * PCollection<T>} to be deterministic (see {@link 
Coder#verifyDeterministic()}). If the
+   * collection {@code Coder} is not deterministic, an exception is thrown at 
pipeline construction
+   * time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of first in {@code PCollectionList<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   * PCollection<String> first = p.apply(Create.of("1","1","2"));
+   * PCollection<String> second = p.apply(Create.of("1", "3", "4","4"));
+   * PCollection<String> third = p.apply(Create.of("1", "5"));

Review comment:
       Thanks.Done

##########
File path: 
sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/SetFns.java
##########
@@ -0,0 +1,618 @@
+/*
+ * 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.beam.sdk.transforms;
+
+import static 
org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkArgument;
+import static 
org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkNotNull;
+
+import java.util.ArrayList;
+import java.util.List;
+import org.apache.beam.sdk.Pipeline;
+import org.apache.beam.sdk.coders.Coder;
+import org.apache.beam.sdk.transforms.join.CoGbkResult;
+import org.apache.beam.sdk.transforms.join.CoGroupByKey;
+import org.apache.beam.sdk.transforms.join.KeyedPCollectionTuple;
+import org.apache.beam.sdk.transforms.windowing.Trigger;
+import org.apache.beam.sdk.transforms.windowing.WindowFn;
+import org.apache.beam.sdk.values.KV;
+import org.apache.beam.sdk.values.PCollection;
+import org.apache.beam.sdk.values.PCollectionList;
+import org.apache.beam.sdk.values.TupleTag;
+import 
org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.Iterables;
+
+public class SetFns {

Review comment:
       Thanks.Done

##########
File path: 
sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/SetFns.java
##########
@@ -0,0 +1,618 @@
+/*
+ * 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.beam.sdk.transforms;
+
+import static 
org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkArgument;
+import static 
org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkNotNull;
+
+import java.util.ArrayList;
+import java.util.List;
+import org.apache.beam.sdk.Pipeline;
+import org.apache.beam.sdk.coders.Coder;
+import org.apache.beam.sdk.transforms.join.CoGbkResult;
+import org.apache.beam.sdk.transforms.join.CoGroupByKey;
+import org.apache.beam.sdk.transforms.join.KeyedPCollectionTuple;
+import org.apache.beam.sdk.transforms.windowing.Trigger;
+import org.apache.beam.sdk.transforms.windowing.WindowFn;
+import org.apache.beam.sdk.values.KV;
+import org.apache.beam.sdk.values.PCollection;
+import org.apache.beam.sdk.values.PCollectionList;
+import org.apache.beam.sdk.values.TupleTag;
+import 
org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.Iterables;
+
+public class SetFns {
+
+  /**
+   * Returns a new {@code PTransform} transform that follows SET DISTINCT 
semantics to compute the
+   * intersection with provided {@code PCollection<T>}.
+   *
+   * <p>The argument should not be modified after this is called.
+   *
+   * <p>The elements of the output {@link PCollection} will all distinct 
elements that present in
+   * both pipeline is constructed and provided {@link PCollection}.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of {@code PCollection<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   *
+   * PCollection<String> left = p.apply(Create.of("1", "2", "3", "3","4", 
"5"));
+   * PCollection<String> right = p.apply(Create.of("1", "3", "4","4", "6"));
+   *
+   * PCollection<String> results =
+   *     left.apply(SetFns.intersectDistinct(right)); // results will be 
PCollection<String> containing: "1","3","4"
+   *
+   * }</pre>
+   *
+   * @param <T> the type of the elements in the input and output {@code 
PCollection<T>}s.
+   */
+  public static <T> SetImpl<T> intersectDistinct(PCollection<T> 
rightCollection) {
+    checkNotNull(rightCollection, "rightCollection argument is null");
+    return new SetImpl<>(rightCollection, intersectDistinct());
+  }
+
+  /**
+   * Returns a {@code PTransform} that takes a {@code 
PCollectionList<PCollection<T>>} and returns a
+   * {@code PCollection<T>} containing intersection of collections done in 
order for all collections
+   * in {@code PCollectionList<T>}.
+   *
+   * <p>Returns a new {@code PTransform} transform that follows SET DISTINCT 
semantics which takes a
+   * {@code PCollectionList<PCollection<T>>} and returns a {@code 
PCollection<T>} containing
+   * intersection of collections done in order for all collections in {@code 
PCollectionList<T>}.
+   *
+   * <p>The elements of the output {@link PCollection} will have all distinct 
elements that are
+   * present in both pipeline is constructed and next {@link PCollection} in 
the list and applied to
+   * all collections in order.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of first in {@code PCollectionList<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   *
+   * PCollection<String> first = p.apply(Create.of("1", "2", "3", "3","4", 
"5"));
+   * PCollection<String> second = p.apply(Create.of("1", "3", "4","4", "6"));
+   * PCollection<String> third = p.apply(Create.of("3", "4","4"));
+   *
+   * // Following example will perform (first intersect second) intersect 
third.
+   * PCollection<String> results =
+   *     PCollectionList.of(first).and(second).and(third)
+   *     .apply(SetFns.intersectDistinct()); // results will be 
PCollection<String> containing: "3","4"
+   *
+   * }</pre>
+   *
+   * @param <T> the type of the elements in the input {@code 
PCollectionList<T>} and output {@code
+   *     PCollection<T>}s.
+   */
+  public static <T> SetImplCollections<T> intersectDistinct() {
+    SerializableBiFunction<Long, Long, Long> intersectFn =
+        (numberOfElementsinLeft, numberOfElementsinRight) ->
+            (numberOfElementsinLeft > 0 && numberOfElementsinRight > 0) ? 1L : 
0L;
+    return new SetImplCollections<>(intersectFn);
+  }
+
+  /**
+   * Returns a new {@code PTransform} transform that follows SET ALL semantics 
to compute the
+   * intersection with provided {@code PCollection<T>}.
+   *
+   * <p>The argument should not be modified after this is called.
+   *
+   * <p>The elements of the output {@link PCollection} which will follow 
INTESECT_ALL Semantics as
+   * follows: Given there are m elements on pipeline which is constructed 
{@link PCollection} (left)
+   * and n elements on in provided {@link PCollection} (right): - it will 
output MIN(m - n, 0)
+   * elements of left for all elements which are present in both left and 
right.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of {@code PCollection<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   *
+   * PCollection<String> left = p.apply(Create.of("1","1","1", "2", "3", 
"3","4", "5"));
+   * PCollection<String> right = p.apply(Create.of("1","1", "3", "4","4", 
"6"));
+   *
+   * PCollection<String> results =
+   *     left.apply(SetFns.intersectAll(right)); // results will be 
PCollection<String> containing: "1","1","3","4"
+   * }</pre>
+   *
+   * @param <T> the type of the elements in the input and output {@code 
PCollection<T>}s.
+   */
+  public static <T> SetImpl<T> intersectAll(PCollection<T> rightCollection) {
+    checkNotNull(rightCollection, "rightCollection argument is null");
+    return new SetImpl<>(rightCollection, intersectAll());
+  }
+
+  /**
+   * Returns a new {@code PTransform} transform that follows SET ALL semantics 
which takes a {@code
+   * PCollectionList<PCollection<T>>} and returns a {@code PCollection<T>} 
containing intersection
+   * all of collections done in order for all collections in {@code 
PCollectionList<T>}.
+   *
+   * <p>The elements of the output {@link PCollection} which will follow 
INTERSECT_ALL semantics.
+   * Output is calculated as follows: Given there are m elements on pipeline 
which is constructed
+   * {@link PCollection} (left) and n elements on in provided {@link 
PCollection} (right): - it will
+   * output MIN(m - n, 0) elements of left for all elements which are present 
in both left and
+   * right.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of first in {@code PCollectionList<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   * PCollection<String> first = p.apply(Create.of("1","1","1", "2", "3", 
"3","4", "5"));
+   * PCollection<String> second = p.apply(Create.of("1","1", "3", "4","4", 
"6"));
+   * PCollection<String> third = p.apply(Create.of("1", "5"));
+   *
+   * // Following example will perform (first intersect second) intersect 
third.
+   * PCollection<String> results =
+   *     PCollectionList.of(first).and(second).and(third)
+   *     .apply(SetFns.intersectAll()); // results will be PCollection<String> 
containing: "1"
+   *
+   * }</pre>
+   *
+   * @param <T> the type of the elements in the input {@code 
PCollectionList<T>} and output {@code
+   *     PCollection<T>}s.
+   */
+  public static <T> SetImplCollections<T> intersectAll() {
+    return new SetImplCollections<>(Math::min);
+  }
+
+  /**
+   * Returns a new {@code PTransform} transform that follows SET DISTINCT 
semantics to compute the
+   * difference (except) with provided {@code PCollection<T>}.
+   *
+   * <p>The argument should not be modified after this is called.
+   *
+   * <p>The elements of the output {@link PCollection} will all distinct 
elements that present in
+   * pipeline is constructed but not present in provided {@link PCollection}.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of {@code PCollection<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   *
+   * PCollection<String> left = p.apply(Create.of("1","1","1", "2", "3", 
"3","4", "5"));
+   * PCollection<String> right = p.apply(Create.of("1","1", "3", "4","4", 
"6"));
+   *
+   * PCollection<String> results =
+   *     left.apply(SetFns.exceptDistinct(right)); // results will be 
PCollection<String> containing: "2","5"
+   * }</pre>
+   *
+   * @param <T> the type of the elements in the input and output {@code 
PCollection<T>}s.
+   */
+  public static <T> SetImpl<T> exceptDistinct(PCollection<T> rightCollection) {
+    checkNotNull(rightCollection, "rightCollection argument is null");
+    return new SetImpl<>(rightCollection, exceptDistinct());
+  }
+
+  /**
+   * Returns a {@code PTransform} that takes a {@code 
PCollectionList<PCollection<T>>} and returns a
+   * {@code PCollection<T>} containing difference (except) of collections done 
in order for all
+   * collections in {@code PCollectionList<T>}.
+   *
+   * <p>Returns a new {@code PTransform} transform that follows SET DISTINCT 
semantics which takes a
+   * {@code PCollectionList<PCollection<T>>} and returns a {@code 
PCollection<T>} containing
+   * difference (except) of collections done in order for all collections in 
{@code
+   * PCollectionList<T>}.
+   *
+   * <p>The elements of the output {@link PCollection} will have all distinct 
elements that are
+   * present in pipeline is constructed but not present in next {@link 
PCollection} in the list and
+   * applied to all collections in order.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of first in {@code PCollectionList<T>}

Review comment:
       Thanks.Done

##########
File path: 
sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/SetFns.java
##########
@@ -0,0 +1,618 @@
+/*
+ * 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.beam.sdk.transforms;
+
+import static 
org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkArgument;
+import static 
org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkNotNull;
+
+import java.util.ArrayList;
+import java.util.List;
+import org.apache.beam.sdk.Pipeline;
+import org.apache.beam.sdk.coders.Coder;
+import org.apache.beam.sdk.transforms.join.CoGbkResult;
+import org.apache.beam.sdk.transforms.join.CoGroupByKey;
+import org.apache.beam.sdk.transforms.join.KeyedPCollectionTuple;
+import org.apache.beam.sdk.transforms.windowing.Trigger;
+import org.apache.beam.sdk.transforms.windowing.WindowFn;
+import org.apache.beam.sdk.values.KV;
+import org.apache.beam.sdk.values.PCollection;
+import org.apache.beam.sdk.values.PCollectionList;
+import org.apache.beam.sdk.values.TupleTag;
+import 
org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.Iterables;
+
+public class SetFns {
+
+  /**
+   * Returns a new {@code PTransform} transform that follows SET DISTINCT 
semantics to compute the
+   * intersection with provided {@code PCollection<T>}.
+   *
+   * <p>The argument should not be modified after this is called.
+   *
+   * <p>The elements of the output {@link PCollection} will all distinct 
elements that present in
+   * both pipeline is constructed and provided {@link PCollection}.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of {@code PCollection<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   *
+   * PCollection<String> left = p.apply(Create.of("1", "2", "3", "3","4", 
"5"));
+   * PCollection<String> right = p.apply(Create.of("1", "3", "4","4", "6"));
+   *
+   * PCollection<String> results =
+   *     left.apply(SetFns.intersectDistinct(right)); // results will be 
PCollection<String> containing: "1","3","4"
+   *
+   * }</pre>
+   *
+   * @param <T> the type of the elements in the input and output {@code 
PCollection<T>}s.
+   */
+  public static <T> SetImpl<T> intersectDistinct(PCollection<T> 
rightCollection) {
+    checkNotNull(rightCollection, "rightCollection argument is null");
+    return new SetImpl<>(rightCollection, intersectDistinct());
+  }
+
+  /**
+   * Returns a {@code PTransform} that takes a {@code 
PCollectionList<PCollection<T>>} and returns a
+   * {@code PCollection<T>} containing intersection of collections done in 
order for all collections
+   * in {@code PCollectionList<T>}.
+   *
+   * <p>Returns a new {@code PTransform} transform that follows SET DISTINCT 
semantics which takes a
+   * {@code PCollectionList<PCollection<T>>} and returns a {@code 
PCollection<T>} containing
+   * intersection of collections done in order for all collections in {@code 
PCollectionList<T>}.
+   *
+   * <p>The elements of the output {@link PCollection} will have all distinct 
elements that are
+   * present in both pipeline is constructed and next {@link PCollection} in 
the list and applied to
+   * all collections in order.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of first in {@code PCollectionList<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   *
+   * PCollection<String> first = p.apply(Create.of("1", "2", "3", "3","4", 
"5"));
+   * PCollection<String> second = p.apply(Create.of("1", "3", "4","4", "6"));
+   * PCollection<String> third = p.apply(Create.of("3", "4","4"));
+   *
+   * // Following example will perform (first intersect second) intersect 
third.
+   * PCollection<String> results =
+   *     PCollectionList.of(first).and(second).and(third)
+   *     .apply(SetFns.intersectDistinct()); // results will be 
PCollection<String> containing: "3","4"
+   *
+   * }</pre>
+   *
+   * @param <T> the type of the elements in the input {@code 
PCollectionList<T>} and output {@code
+   *     PCollection<T>}s.
+   */
+  public static <T> SetImplCollections<T> intersectDistinct() {
+    SerializableBiFunction<Long, Long, Long> intersectFn =
+        (numberOfElementsinLeft, numberOfElementsinRight) ->
+            (numberOfElementsinLeft > 0 && numberOfElementsinRight > 0) ? 1L : 
0L;
+    return new SetImplCollections<>(intersectFn);
+  }
+
+  /**
+   * Returns a new {@code PTransform} transform that follows SET ALL semantics 
to compute the
+   * intersection with provided {@code PCollection<T>}.
+   *
+   * <p>The argument should not be modified after this is called.
+   *
+   * <p>The elements of the output {@link PCollection} which will follow 
INTESECT_ALL Semantics as
+   * follows: Given there are m elements on pipeline which is constructed 
{@link PCollection} (left)
+   * and n elements on in provided {@link PCollection} (right): - it will 
output MIN(m - n, 0)
+   * elements of left for all elements which are present in both left and 
right.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of {@code PCollection<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   *
+   * PCollection<String> left = p.apply(Create.of("1","1","1", "2", "3", 
"3","4", "5"));
+   * PCollection<String> right = p.apply(Create.of("1","1", "3", "4","4", 
"6"));
+   *
+   * PCollection<String> results =
+   *     left.apply(SetFns.intersectAll(right)); // results will be 
PCollection<String> containing: "1","1","3","4"
+   * }</pre>
+   *
+   * @param <T> the type of the elements in the input and output {@code 
PCollection<T>}s.
+   */
+  public static <T> SetImpl<T> intersectAll(PCollection<T> rightCollection) {
+    checkNotNull(rightCollection, "rightCollection argument is null");
+    return new SetImpl<>(rightCollection, intersectAll());
+  }
+
+  /**
+   * Returns a new {@code PTransform} transform that follows SET ALL semantics 
which takes a {@code
+   * PCollectionList<PCollection<T>>} and returns a {@code PCollection<T>} 
containing intersection
+   * all of collections done in order for all collections in {@code 
PCollectionList<T>}.
+   *
+   * <p>The elements of the output {@link PCollection} which will follow 
INTERSECT_ALL semantics.
+   * Output is calculated as follows: Given there are m elements on pipeline 
which is constructed
+   * {@link PCollection} (left) and n elements on in provided {@link 
PCollection} (right): - it will
+   * output MIN(m - n, 0) elements of left for all elements which are present 
in both left and
+   * right.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of first in {@code PCollectionList<T>}

Review comment:
       Thanks.Done

##########
File path: 
sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/SetFns.java
##########
@@ -0,0 +1,618 @@
+/*
+ * 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.beam.sdk.transforms;
+
+import static 
org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkArgument;
+import static 
org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkNotNull;
+
+import java.util.ArrayList;
+import java.util.List;
+import org.apache.beam.sdk.Pipeline;
+import org.apache.beam.sdk.coders.Coder;
+import org.apache.beam.sdk.transforms.join.CoGbkResult;
+import org.apache.beam.sdk.transforms.join.CoGroupByKey;
+import org.apache.beam.sdk.transforms.join.KeyedPCollectionTuple;
+import org.apache.beam.sdk.transforms.windowing.Trigger;
+import org.apache.beam.sdk.transforms.windowing.WindowFn;
+import org.apache.beam.sdk.values.KV;
+import org.apache.beam.sdk.values.PCollection;
+import org.apache.beam.sdk.values.PCollectionList;
+import org.apache.beam.sdk.values.TupleTag;
+import 
org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.Iterables;
+
+public class SetFns {
+
+  /**
+   * Returns a new {@code PTransform} transform that follows SET DISTINCT 
semantics to compute the
+   * intersection with provided {@code PCollection<T>}.
+   *
+   * <p>The argument should not be modified after this is called.
+   *
+   * <p>The elements of the output {@link PCollection} will all distinct 
elements that present in
+   * both pipeline is constructed and provided {@link PCollection}.
+   *
+   * <p>Note that this transform requires that the {@code Coder} of the all 
{@code PCollection<T>}
+   * to be deterministic (see {@link Coder#verifyDeterministic()}). If the 
collection {@code Coder}
+   * is not deterministic, an exception is thrown at pipeline construction 
time.
+   *
+   * <p>All inputs must have equal {@link WindowFn}s and compatible triggers 
(see {@link
+   * Trigger#isCompatible(Trigger)}).
+   *
+   * <p>By default, the output {@code PCollection<T>} encodes its elements 
using the same {@code
+   * Coder} that of {@code PCollection<T>}
+   *
+   * <pre>{@code
+   * Pipeline p = ...;
+   *
+   * PCollection<String> left = p.apply(Create.of("1", "2", "3", "3","4", 
"5"));
+   * PCollection<String> right = p.apply(Create.of("1", "3", "4","4", "6"));
+   *
+   * PCollection<String> results =
+   *     left.apply(SetFns.intersectDistinct(right)); // results will be 
PCollection<String> containing: "1","3","4"
+   *
+   * }</pre>
+   *
+   * @param <T> the type of the elements in the input and output {@code 
PCollection<T>}s.
+   */
+  public static <T> SetImpl<T> intersectDistinct(PCollection<T> 
rightCollection) {
+    checkNotNull(rightCollection, "rightCollection argument is null");
+    return new SetImpl<>(rightCollection, intersectDistinct());
+  }
+
+  /**
+   * Returns a {@code PTransform} that takes a {@code 
PCollectionList<PCollection<T>>} and returns a
+   * {@code PCollection<T>} containing intersection of collections done in 
order for all collections
+   * in {@code PCollectionList<T>}.
+   *
+   * <p>Returns a new {@code PTransform} transform that follows SET DISTINCT 
semantics which takes a
+   * {@code PCollectionList<PCollection<T>>} and returns a {@code 
PCollection<T>} containing

Review comment:
       Thanks.Done




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