[Feature](function) support function array_combinations

be/src/exprs/function/array/function_array_combinations.cpp

@@ -0,0 +1,187 @@
+// 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.
+
+#include "common/compiler_util.h"
+#include "common/status.h"
+#include "core/assert_cast.h"
+#include "core/column/column_array.h"
+#include "core/column/column_const.h"
+#include "core/data_type/data_type.h"
+#include "core/data_type/data_type_array.h"
+#include "core/data_type/data_type_decimal.h"
+#include "core/data_type/data_type_nullable.h"
+#include "core/types.h"
+#include "exprs/function/function.h"
+#include "exprs/function/function_helpers.h"
+#include "exprs/function/simple_function_factory.h"
+
+namespace doris {
+// array_combinations([1, 2, 3],2) -> [[1,2], [1,3], [2,3]]
+// array_combinations([1, NULL, 3, NULL, 5]，4) -> [[1,NULL,3,NULL], [1,NULL,3,5], [NULL,3,NULL,5]]
+
+class FunctionArrayCombinations : public IFunction {
+public:
+    static constexpr auto name = "array_combinations";
+    static FunctionPtr create() { return std::make_shared<FunctionArrayCombinations>(); }
+    bool is_variadic() const override { return false; }
+    String get_name() const override { return name; }
+
+    size_t get_number_of_arguments() const override { return 2; }
+
+    bool use_default_implementation_for_nulls() const override { return true; }
+
+    DataTypePtr get_return_type_impl(const DataTypes& arguments) const override {
+        const auto* array_type = assert_cast<const DataTypeArray*>(arguments[0].get());
+        auto elem_t = make_nullable(array_type->get_nested_type());
+        auto res = std::make_shared<DataTypeArray>(
+                make_nullable(std::make_shared<DataTypeArray>(elem_t)));
+        return res;
+    }
+
+    Status execute_impl(FunctionContext* context, Block& block, const ColumnNumbers& arguments,
+                        uint32_t result, size_t input_rows_count) const override {
+        auto array = block.get_by_position(arguments[0]).column;
+        ColumnPtr num = block.get_by_position(arguments[1]).column;
+        Int64 combination_length = num->get_int(0);
+
+        if (combination_length > MAX_COMBINATION_LENGTH || combination_length < 1) {
+            return Status::InvalidArgument(
+                    fmt::format("execute failed, function {}'s second argument must be bigger than "
+                                "0 and not bigger than 5",
+                                get_name()));
+        }
+
+        ColumnPtr res;
+        const auto* src_arr = assert_cast<const ColumnArray*>(remove_nullable(array).get());
+        const auto& offsets =
+                assert_cast<const ColumnArray::ColumnOffsets&>(src_arr->get_offsets_column());
+        Status status = vector_const(src_arr, input_rows_count, res, offsets, combination_length);
+        if (!status.ok()) {
+            return status;
+        }
+        block.replace_by_position(result, std::move(res));
+        return status;
+    }
+
+    ColumnNumbers get_arguments_that_are_always_constant() const override { return {1}; }
+
+private:
+    static const size_t MAX_COMBINATION_LENGTH = 5;
+    static const size_t MAX_COMBINATION_COUNT = 100000;
+
+    // Then combinationCount(n, k) = combinationCount(n-1, k-1) * n/k (https://en.wikipedia.org/wiki/Combination#Number_of_k-combinations)
+    // The formula is recursive. Here, instead of starting with k=combinationCount, n=arrayLength and recursing,
+    // we start with k=0 n=(arrayLength-combinationLength) and proceed "bottom up".
+    size_t _combination_count(size_t array_length, size_t combination_length) const {
+        size_t combinations = 1;
+
+        for (size_t i = 1; i <= combination_length; i++) {
+            combinations = combinations * (array_length - combination_length + i) / i;
+        }
+
+        return combinations;
+    }
+
+    ALWAYS_INLINE std::vector<size_t> _first_combination(Int64 combination_length,
+                                                         size_t length) const {
+        std::vector<size_t> comb(combination_length + 1);
+        std::iota(comb.begin(), comb.begin() + combination_length, 0);
+        comb[combination_length] = length;
+        return comb;
+    }
+
+    // Generates the next k-combination in colex order.
+    //
+    // scan from the lowest index upward and increment the first
+    // position that can be increased without breaking the strictly
+    // increasing invariant. Resetting all lower positions to their
+    // minimal values ensures the result is the smallest combination
+    // greater than the current one.
+    bool _next_combination(std::vector<size_t>& comb, Int64 combination_length) const {
+        for (size_t i = 0; i < combination_length; ++i) {
+            if (comb[i] + 1 < comb[i + 1]) {
+                ++comb[i];
+                std::iota(comb.begin(), comb.begin() + i, 0);
+                return true;
+            }
+        }
+        return false;
+    }
+
+    Status vector_const(const ColumnArray* nested_src_column_ptr, size_t input_rows_count,
+                        ColumnPtr& res, const ColumnArray::ColumnOffsets& offsets,
+                        Int64 combination_length) const {
+        const auto& src_data = nested_src_column_ptr->get_data();
+        const auto& src_offsets = offsets.get_data();
+
+        auto inner_data = src_data.clone_empty();
+        auto inner_offsets = ColumnArray::ColumnOffsets::create();
+        auto inner_arr = ColumnArray::create(std::move(inner_data), std::move(inner_offsets));
+        auto* inner = assert_cast<ColumnArray*>(inner_arr.get());
+
+        auto outer_offsets = ColumnArray::ColumnOffsets::create();
+        auto& outer_offsets_data = outer_offsets->get_data();
+        outer_offsets_data.resize(input_rows_count);
+
+        size_t prev_off = 0, outer_off = 0;
+
+        for (size_t row = 0; row < input_rows_count; ++row) {
+            size_t curr_off = src_offsets[row];
+            size_t row_len = curr_off - prev_off;
+
+            if (combination_length <= 0 || combination_length > row_len) {
+                outer_offsets_data[row] = outer_off;
+                prev_off = curr_off;
+                continue;
+            }
+
+            size_t combination_count = _combination_count(row_len, combination_length);
+            if (combination_count > MAX_COMBINATION_COUNT) {
+                return Status::InvalidArgument(
+                        fmt::format("execute failed, function {}'s total size of sub-groups "
+                                    "generated must be smaller than 100,000",
+                                    get_name()));
+            }
+            std::vector comb = _first_combination(combination_length, row_len);
+            inner->get_data().reserve(inner->get_data().size() +
+                                      combination_count * combination_length);
+            inner->get_offsets().reserve(inner->get_offsets().size() + combination_count);
+            outer_off += combination_count;
+            do {
+                for (int i = 0; i < combination_length; ++i) {
+                    size_t idx = prev_off + comb[i];
+                    inner->get_data().insert_from(src_data, idx);
+                }
+                inner->get_offsets().push_back(inner->get_data().size());
+            } while (_next_combination(comb, combination_length));
+
+            outer_offsets_data[row] = outer_off;
+            prev_off = curr_off;
+        }
+        size_t inner_size = inner_arr->size();
+        auto nullable_arr =
+                ColumnNullable::create(std::move(inner_arr), ColumnUInt8::create(inner_size, 0));
+        res = ColumnArray::create(std::move(nullable_arr), std::move(outer_offsets));
+
+        return Status::OK();
+    }
+};
+
+void register_function_array_combinations(SimpleFunctionFactory& factory) {
+    factory.register_function<FunctionArrayCombinations>();
+}
+} // namespace doris

be/src/exprs/function/array/function_array_register.cpp

@@ -57,6 +57,7 @@ void register_function_array_filter_function(SimpleFunctionFactory&);
 void register_function_array_splits(SimpleFunctionFactory&);
 void register_function_array_contains_all(SimpleFunctionFactory&);
 void register_function_array_match(SimpleFunctionFactory&);
+void register_function_array_combinations(SimpleFunctionFactory&);
 
 void register_function_array(SimpleFunctionFactory& factory) {
     register_function_array_flatten(factory);
@@ -95,6 +96,7 @@ void register_function_array(SimpleFunctionFactory& factory) {
     register_function_array_splits(factory);
     register_function_array_contains_all(factory);
     register_function_array_match(factory);
+    register_function_array_combinations(factory);
 }
 
 } // namespace doris

fe/fe-core/src/main/java/org/apache/doris/catalog/BuiltinScalarFunctions.java

@@ -40,6 +40,7 @@
 import org.apache.doris.nereids.trees.expressions.functions.scalar.Array;
 import org.apache.doris.nereids.trees.expressions.functions.scalar.ArrayApply;
 import org.apache.doris.nereids.trees.expressions.functions.scalar.ArrayAvg;
+import org.apache.doris.nereids.trees.expressions.functions.scalar.ArrayCombinations;
 import org.apache.doris.nereids.trees.expressions.functions.scalar.ArrayCompact;
 import org.apache.doris.nereids.trees.expressions.functions.scalar.ArrayConcat;
 import org.apache.doris.nereids.trees.expressions.functions.scalar.ArrayContains;
@@ -623,6 +624,7 @@ public class BuiltinScalarFunctions implements FunctionHelper {
             scalar(ArrayFirst.class, "array_first"),
             scalar(ArrayFirstIndex.class, "array_first_index"),
             scalar(ArrayFlatten.class, "array_flatten"),
+            scalar(ArrayCombinations.class, "array_combinations"),
             scalar(ArrayIntersect.class, "array_intersect"),
             scalar(ArrayJoin.class, "array_join"),
             scalar(ArrayLast.class, "array_last"),

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/ArrayCombinations.java

@@ -0,0 +1,85 @@
+// 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.doris.nereids.trees.expressions.functions.scalar;
+
+import org.apache.doris.catalog.FunctionSignature;
+import org.apache.doris.nereids.exceptions.AnalysisException;
+import org.apache.doris.nereids.trees.expressions.Expression;
+import org.apache.doris.nereids.trees.expressions.functions.ExplicitlyCastableSignature;
+import org.apache.doris.nereids.trees.expressions.functions.PropagateNullable;
+import org.apache.doris.nereids.trees.expressions.literal.IntegerLikeLiteral;
+import org.apache.doris.nereids.trees.expressions.literal.NullLiteral;
+import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor;
+import org.apache.doris.nereids.types.ArrayType;
+import org.apache.doris.nereids.types.BigIntType;
+import org.apache.doris.nereids.types.coercion.AnyDataType;
+import org.apache.doris.nereids.types.coercion.FollowToAnyDataType;
+
+import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableList;
+
+import java.util.List;
+
+/**
+ * ScalarFunction 'combinations'
+ */
+public class ArrayCombinations extends ScalarFunction
+        implements ExplicitlyCastableSignature, PropagateNullable {
+
+    public static final List<FunctionSignature> SIGNATURES = ImmutableList.of(
+            FunctionSignature.ret(ArrayType.of(ArrayType.of(new FollowToAnyDataType(0))))
+                    .args(ArrayType.of(new AnyDataType(0)), BigIntType.INSTANCE));
+
+    /**
+     * constructor with 2 arguments.
+     */
+    public ArrayCombinations(Expression arg0, Expression arg1) {
+        super("array_combinations", arg0, arg1);
+    }
+
+    @Override
+    public void checkLegalityBeforeTypeCoercion() {
+        if (!(child(1) instanceof IntegerLikeLiteral || child(1) instanceof NullLiteral)) {
+            throw new AnalysisException("Array_Combinations's second argument must be a constant literal.");
+        }
+    }
+
+    @Override
+    public void checkLegalityAfterRewrite() {
+        checkLegalityBeforeTypeCoercion();
+    }
+
+    @Override
+    public List<FunctionSignature> getSignatures() {
+        return SIGNATURES;
+    }
+
+    /**
+     * withChildren.
+     */
+    @Override
+    public ArrayCombinations withChildren(List<Expression> children) {
+        Preconditions.checkArgument(children.size() == 2);
+        return new ArrayCombinations(children.get(0), children.get(1));
+    }
+
+    @Override
+    public <R, C> R accept(ExpressionVisitor<R, C> visitor, C context) {
+        return visitor.visitArrayCombinations(this, context);
+    }
+}

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/visitor/ScalarFunctionVisitor.java

@@ -42,6 +42,7 @@
 import org.apache.doris.nereids.trees.expressions.functions.scalar.Array;
 import org.apache.doris.nereids.trees.expressions.functions.scalar.ArrayApply;
 import org.apache.doris.nereids.trees.expressions.functions.scalar.ArrayAvg;
+import org.apache.doris.nereids.trees.expressions.functions.scalar.ArrayCombinations;
 import org.apache.doris.nereids.trees.expressions.functions.scalar.ArrayCompact;
 import org.apache.doris.nereids.trees.expressions.functions.scalar.ArrayConcat;
 import org.apache.doris.nereids.trees.expressions.functions.scalar.ArrayContains;
@@ -823,6 +824,10 @@ default R visitArrayFlatten(ArrayFlatten arrayFlatten, C context) {
         return visitScalarFunction(arrayFlatten, context);
     }
 
+    default R visitArrayCombinations(ArrayCombinations arrayCombinations, C context) {
+        return visitScalarFunction(arrayCombinations, context);
+    }
+
     default R visitArrayMap(ArrayMap arrayMap, C context) {
         return visitScalarFunction(arrayMap, context);
     }

regression-test/data/nereids_function_p0/scalar_function/Array.out

@@ -16128,3 +16128,20 @@ false	false
 -- !sql --
 [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
 
+-- !sql --
+[["foo", "bar"], ["foo", "baz"], ["bar", "baz"]]
+
+-- !sql --
+[[1, 2], [1, 3], [2, 3]]
+
+-- !sql --
+[[1, 2], [1, 2], [2, 2]]
+
+-- !sql --
+[]
+
+-- !sql --
+[[null], [null]]
+
+-- !sql --
+[[[[1, 2, 3, 4, 5]], [[6, 7], [8, 9]]]]