dhruv9vats commented on a change in pull request #12162:
URL: https://github.com/apache/arrow/pull/12162#discussion_r791739035
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File path: cpp/src/arrow/compute/kernels/scalar_nested.cc
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@@ -429,6 +429,167 @@ const FunctionDoc make_struct_doc{"Wrap Arrays into a
StructArray",
{"*args"},
"MakeStructOptions"};
+struct MapArrayLookupFunctor {
+ static Result<int64_t> FindOneMapValueIndex(const Array& keys, const Scalar&
query_key,
+ const int64_t start, const
int64_t end,
+ const bool from_back = false) {
+ if (!from_back) {
+ for (int64_t idx = start; idx < end; ++idx) {
+ ARROW_ASSIGN_OR_RAISE(std::shared_ptr<Scalar> key,
keys.GetScalar(idx));
+
+ if (key->Equals(query_key)) return idx;
+ }
+ } else {
+ for (int64_t idx = end - 1; idx >= start; --idx) {
+ ARROW_ASSIGN_OR_RAISE(std::shared_ptr<Scalar> key,
keys.GetScalar(idx));
+
+ if (key->Equals(query_key)) return idx;
+ }
+ }
+ return -1;
+ }
+
+ static Status SetScalarOutput(const Array& keys, const Array& items,
KernelContext* ctx,
+ const MapArrayLookupOptions& options,
+ std::shared_ptr<Scalar>& out) {
+ const Scalar& query_key = *options.query_key;
+ if (options.occurrence == MapArrayLookupOptions::Occurrence::ALL) {
+ std::unique_ptr<ArrayBuilder> builder;
+ RETURN_NOT_OK(MakeBuilder(ctx->memory_pool(), items.type(), &builder));
+
+ bool found_at_least_one_key = false;
+ for (int64_t idx = 0; idx < keys.length(); ++idx) {
+ ARROW_ASSIGN_OR_RAISE(std::shared_ptr<Scalar> key,
keys.GetScalar(idx));
+
+ if (key->Equals(query_key)) {
+ found_at_least_one_key = true;
+ RETURN_NOT_OK(builder->AppendArraySlice(*items.data(), idx, 1));
+ }
+ }
+ if (!found_at_least_one_key) {
+ out = MakeNullScalar(list(items.type()));
+ } else {
+ ARROW_ASSIGN_OR_RAISE(auto result, builder->Finish());
+ ARROW_ASSIGN_OR_RAISE(out, MakeScalar(list(items.type()), result));
+ }
+ } else { /* occurrence == FIRST || LAST */
+ bool from_back = (options.occurrence == MapArrayLookupOptions::LAST);
+
+ ARROW_ASSIGN_OR_RAISE(
+ int64_t key_match_idx,
+ FindOneMapValueIndex(keys, query_key, 0, keys.length(), from_back));
+ if (key_match_idx != -1) {
+ ARROW_ASSIGN_OR_RAISE(out, items.GetScalar(key_match_idx));
+ } else {
+ out = MakeNullScalar(items.type());
+ }
+ }
+ return Status::OK();
+ }
+
+ static Status ExecMapArray(KernelContext* ctx, const ExecBatch& batch,
Datum* out) {
+ const auto& options = OptionsWrapper<MapArrayLookupOptions>::Get(ctx);
+
+ const MapArray map_array(batch[0].array());
+
+ std::unique_ptr<ArrayBuilder> builder;
+ if (options.occurrence == MapArrayLookupOptions::Occurrence::ALL) {
+ RETURN_NOT_OK(MakeBuilder(ctx->memory_pool(),
+ list(map_array.map_type()->item_type()),
&builder));
+ } else {
+ RETURN_NOT_OK(
+ MakeBuilder(ctx->memory_pool(), map_array.map_type()->item_type(),
&builder));
+ }
+
+ for (int64_t map_array_idx = 0; map_array_idx < map_array.length();
++map_array_idx) {
+ if (!map_array.IsValid(map_array_idx)) {
+ RETURN_NOT_OK(builder->AppendNull());
+ continue;
+ } else {
+ auto map = map_array.value_slice(map_array_idx);
+ auto keys = checked_cast<const StructArray&>(*map).field(0);
+ auto items = checked_cast<const StructArray&>(*map).field(1);
+ std::shared_ptr<Scalar> output;
+ RETURN_NOT_OK(SetScalarOutput(*keys, *items, ctx, options, output));
Review comment:
But offsets are only needed in the Array case, as MapScalar ->
StructArray -> field(0, 1) approach for the Scalar case give the
_appropriate_(corresponding just to the given map element from the MapArray)
keys/items anyways.
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