pitrou commented on a change in pull request #8894: URL: https://github.com/apache/arrow/pull/8894#discussion_r545418989
########## File path: cpp/src/arrow/dataset/expression.cc ########## @@ -0,0 +1,1177 @@ +// 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 "arrow/dataset/expression.h" + +#include <unordered_map> +#include <unordered_set> + +#include "arrow/chunked_array.h" +#include "arrow/compute/exec_internal.h" +#include "arrow/dataset/expression_internal.h" +#include "arrow/io/memory.h" +#include "arrow/ipc/reader.h" +#include "arrow/ipc/writer.h" +#include "arrow/util/key_value_metadata.h" +#include "arrow/util/logging.h" +#include "arrow/util/optional.h" +#include "arrow/util/string.h" +#include "arrow/util/value_parsing.h" + +namespace arrow { + +using internal::checked_cast; +using internal::checked_pointer_cast; + +namespace dataset { + +Expression::Expression(Call call) : impl_(std::make_shared<Impl>(std::move(call))) {} + +Expression::Expression(Datum literal) + : impl_(std::make_shared<Impl>(std::move(literal))) {} + +Expression::Expression(Parameter parameter) + : impl_(std::make_shared<Impl>(std::move(parameter))) {} + +Expression literal(Datum lit) { return Expression(std::move(lit)); } + +Expression field_ref(FieldRef ref) { + return Expression(Expression::Parameter{std::move(ref), {}}); +} + +Expression call(std::string function, std::vector<Expression> arguments, + std::shared_ptr<compute::FunctionOptions> options) { + Expression::Call call; + call.function_name = std::move(function); + call.arguments = std::move(arguments); + call.options = std::move(options); + return Expression(std::move(call)); +} + +const Datum* Expression::literal() const { return util::get_if<Datum>(impl_.get()); } + +const FieldRef* Expression::field_ref() const { + if (auto parameter = util::get_if<Parameter>(impl_.get())) { + return ¶meter->ref; + } + return nullptr; +} + +const Expression::Call* Expression::call() const { + return util::get_if<Call>(impl_.get()); +} + +ValueDescr Expression::descr() const { + if (impl_ == nullptr) return {}; + + if (auto lit = literal()) { + return lit->descr(); + } + + if (auto parameter = util::get_if<Parameter>(impl_.get())) { + return parameter->descr; + } + + return CallNotNull(*this)->descr; +} + +std::string Expression::ToString() const { + if (auto lit = literal()) { + if (lit->is_scalar()) { + switch (lit->type()->id()) { + case Type::STRING: + case Type::LARGE_STRING: + return '"' + + Escape(util::string_view(*lit->scalar_as<BaseBinaryScalar>().value)) + + '"'; + + case Type::BINARY: + case Type::FIXED_SIZE_BINARY: + case Type::LARGE_BINARY: + return '"' + lit->scalar_as<BaseBinaryScalar>().value->ToHexString() + '"'; + + default: + break; + } + return lit->scalar()->ToString(); + } + return lit->ToString(); + } + + if (auto ref = field_ref()) { + if (auto name = ref->name()) { + return *name; + } + if (auto path = ref->field_path()) { + return path->ToString(); + } + return ref->ToString(); + } + + auto call = CallNotNull(*this); + auto binary = [&](std::string op) { + return "(" + call->arguments[0].ToString() + " " + op + " " + + call->arguments[1].ToString() + ")"; + }; + + if (auto cmp = Comparison::Get(call->function_name)) { + return binary(Comparison::GetOp(*cmp)); + } + + constexpr util::string_view kleene = "_kleene"; + if (util::string_view{call->function_name}.ends_with(kleene)) { + auto op = call->function_name.substr(0, call->function_name.size() - kleene.size()); + return binary(std::move(op)); + } + + if (auto options = GetStructOptions(*call)) { + std::string out = "{"; + auto argument = call->arguments.begin(); + for (const auto& field_name : options->field_names) { + out += field_name + "=" + argument++->ToString() + ", "; + } + out.resize(out.size() - 1); + out.back() = '}'; + return out; + } + + std::string out = call->function_name + "("; + for (const auto& arg : call->arguments) { + out += arg.ToString() + ", "; + } + + if (call->options == nullptr) { + out.resize(out.size() - 1); + out.back() = ')'; + return out; + } + + if (auto options = GetSetLookupOptions(*call)) { + DCHECK_EQ(options->value_set.kind(), Datum::ARRAY); + out += "value_set=" + options->value_set.make_array()->ToString(); + if (options->skip_nulls) { + out += ", skip_nulls"; + } + return out + ")"; + } + + if (auto options = GetCastOptions(*call)) { + if (options->to_type == nullptr) { + return out + "to_type=<INVALID NOT PROVIDED>)"; + } + out += "to_type=" + options->to_type->ToString(); + if (options->allow_int_overflow) out += ", allow_int_overflow"; + if (options->allow_time_truncate) out += ", allow_time_truncate"; + if (options->allow_time_overflow) out += ", allow_time_overflow"; + if (options->allow_decimal_truncate) out += ", allow_decimal_truncate"; + if (options->allow_float_truncate) out += ", allow_float_truncate"; + if (options->allow_invalid_utf8) out += ", allow_invalid_utf8"; + return out + ")"; + } + + if (auto options = GetStrptimeOptions(*call)) { + return out + "format=" + options->format + + ", unit=" + internal::ToString(options->unit) + ")"; + } + + return out + "{NON-REPRESENTABLE OPTIONS})"; +} + +void PrintTo(const Expression& expr, std::ostream* os) { + *os << expr.ToString(); + if (expr.IsBound()) { + *os << "[bound]"; + } +} + +bool Expression::Equals(const Expression& other) const { + if (Identical(*this, other)) return true; + + if (impl_->index() != other.impl_->index()) { + return false; + } + + if (auto lit = literal()) { + return lit->Equals(*other.literal()); + } + + if (auto ref = field_ref()) { + return ref->Equals(*other.field_ref()); + } + + auto call = CallNotNull(*this); + auto other_call = CallNotNull(other); + + if (call->function_name != other_call->function_name || + call->kernel != other_call->kernel) { + return false; + } + + for (size_t i = 0; i < call->arguments.size(); ++i) { + if (!call->arguments[i].Equals(other_call->arguments[i])) { + return false; + } + } + + if (call->options == other_call->options) return true; + + if (auto options = GetSetLookupOptions(*call)) { + auto other_options = GetSetLookupOptions(*other_call); + return options->value_set == other_options->value_set && + options->skip_nulls == other_options->skip_nulls; + } + + if (auto options = GetCastOptions(*call)) { + auto other_options = GetCastOptions(*other_call); + for (auto safety_opt : { + &compute::CastOptions::allow_int_overflow, + &compute::CastOptions::allow_time_truncate, + &compute::CastOptions::allow_time_overflow, + &compute::CastOptions::allow_decimal_truncate, + &compute::CastOptions::allow_float_truncate, + &compute::CastOptions::allow_invalid_utf8, + }) { + if (options->*safety_opt != other_options->*safety_opt) return false; + } + return options->to_type->Equals(other_options->to_type); + } + + if (auto options = GetStructOptions(*call)) { + auto other_options = GetStructOptions(*other_call); + return options->field_names == other_options->field_names; + } + + if (auto options = GetStrptimeOptions(*call)) { + auto other_options = GetStrptimeOptions(*other_call); + return options->format == other_options->format && + options->unit == other_options->unit; + } + + ARROW_LOG(WARNING) << "comparing unknown FunctionOptions for function " + << call->function_name; + return false; +} + +size_t Expression::hash() const { + if (auto lit = literal()) { + if (lit->is_scalar()) { + return Scalar::Hash::hash(*lit->scalar()); + } + return 0; + } + + if (auto ref = field_ref()) { + return ref->hash(); + } + + auto call = CallNotNull(*this); + + size_t out = std::hash<std::string>{}(call->function_name); + for (const auto& arg : call->arguments) { + out ^= arg.hash(); + } + return out; +} + +bool Expression::IsBound() const { + if (descr().type == nullptr) return false; + + if (auto lit = literal()) return true; + + if (auto ref = field_ref()) return true; + + auto call = CallNotNull(*this); + + for (const Expression& arg : call->arguments) { + if (!arg.IsBound()) return false; + } + + return call->kernel != nullptr; +} + +bool Expression::IsScalarExpression() const { + if (auto lit = literal()) { + return lit->is_scalar(); + } + + // FIXME handle case where a list's item field is referenced + if (auto ref = field_ref()) return true; + + auto call = CallNotNull(*this); + + for (const Expression& arg : call->arguments) { + if (!arg.IsScalarExpression()) return false; + } + + if (call->function) { + return call->function->kind() == compute::Function::SCALAR; + } + + // this expression is not bound; make a best guess based on + // the default function registry + if (auto function = compute::GetFunctionRegistry() + ->GetFunction(call->function_name) + .ValueOr(nullptr)) { + return function->kind() == compute::Function::SCALAR; + } + + // unknown function or other error; conservatively return false + return false; +} + +bool Expression::IsNullLiteral() const { + if (auto lit = literal()) { + if (lit->null_count() == lit->length()) { + return true; + } + } + + return false; +} + +bool Expression::IsSatisfiable() const { + if (descr().type && descr().type->id() == Type::NA) { + return false; + } + + if (auto lit = literal()) { + if (lit->null_count() == lit->length()) { + return false; + } + + if (lit->is_scalar() && lit->type()->id() == Type::BOOL) { + return lit->scalar_as<BooleanScalar>().value; + } + } + + if (auto ref = field_ref()) { + return true; + } + + return true; +} + +inline bool KernelStateIsImmutable(const std::string& function) { + // XXX maybe just add Kernel::state_is_immutable or so? + + // known functions with non-null but nevertheless immutable KernelState + static std::unordered_set<std::string> names = { + "is_in", "index_in", "cast", "struct", "strptime", + }; + + return names.find(function) != names.end(); +} + +Result<std::unique_ptr<compute::KernelState>> InitKernelState( + const Expression::Call& call, compute::ExecContext* exec_context) { + if (!call.kernel->init) return nullptr; + + compute::KernelContext kernel_context(exec_context); + auto kernel_state = call.kernel->init( + &kernel_context, {call.kernel, GetDescriptors(call.arguments), call.options.get()}); + + RETURN_NOT_OK(kernel_context.status()); + return std::move(kernel_state); +} + +Status MaybeInsertCast(std::shared_ptr<DataType> to_type, Expression* expr) { + if (expr->descr().type->Equals(to_type)) { + return Status::OK(); + } + + if (auto lit = expr->literal()) { + ARROW_ASSIGN_OR_RAISE(Datum new_lit, compute::Cast(*lit, to_type)); + *expr = literal(std::move(new_lit)); + return Status::OK(); + } + + // FIXME the resulting cast Call must be bound but this is a hack + auto with_cast = call("cast", {literal(MakeNullScalar(expr->descr().type))}, + compute::CastOptions::Safe(to_type)); + + static ValueDescr ignored_descr; + ARROW_ASSIGN_OR_RAISE(with_cast, with_cast.Bind(ignored_descr)); + + auto call_with_cast = *CallNotNull(with_cast); + call_with_cast.arguments[0] = std::move(*expr); + call_with_cast.descr = ValueDescr{std::move(to_type), expr->descr().shape}; + + *expr = Expression(std::move(call_with_cast)); + return Status::OK(); +} + +Status InsertImplicitCasts(Expression::Call* call) { + DCHECK(std::all_of(call->arguments.begin(), call->arguments.end(), + [](const Expression& argument) { return argument.IsBound(); })); + + if (IsSameTypesBinary(call->function_name)) { + for (auto&& argument : call->arguments) { + if (auto value_type = GetDictionaryValueType(argument.descr().type)) { + RETURN_NOT_OK(MaybeInsertCast(std::move(value_type), &argument)); + } + } + + if (call->arguments[0].descr().shape == ValueDescr::SCALAR) { + // argument 0 is scalar so casting is cheap + return MaybeInsertCast(call->arguments[1].descr().type, &call->arguments[0]); + } + + // cast argument 1 unconditionally + return MaybeInsertCast(call->arguments[0].descr().type, &call->arguments[1]); + } + + if (auto options = GetSetLookupOptions(*call)) { + if (auto value_type = GetDictionaryValueType(call->arguments[0].descr().type)) { + // DICTIONARY input is not supported; decode it. + RETURN_NOT_OK(MaybeInsertCast(std::move(value_type), &call->arguments[0])); + } + + if (options->value_set.type()->id() == Type::DICTIONARY) { + // DICTIONARY value_set is not supported; decode it. + auto new_options = std::make_shared<compute::SetLookupOptions>(*options); + RETURN_NOT_OK(EnsureNotDictionary(&new_options->value_set)); + options = new_options.get(); + call->options = std::move(new_options); + } + + if (!options->value_set.type()->Equals(call->arguments[0].descr().type)) { + // The value_set is assumed smaller than inputs, casting it should be cheaper. + auto new_options = std::make_shared<compute::SetLookupOptions>(*options); + ARROW_ASSIGN_OR_RAISE(new_options->value_set, + compute::Cast(std::move(new_options->value_set), + call->arguments[0].descr().type)); + options = new_options.get(); + call->options = std::move(new_options); + } + + return Status::OK(); + } + + return Status::OK(); +} + +Result<Expression> Expression::Bind(ValueDescr in, + compute::ExecContext* exec_context) const { + if (exec_context == nullptr) { + compute::ExecContext exec_context; + return Bind(std::move(in), &exec_context); + } + + if (literal()) return *this; + + if (auto ref = field_ref()) { + ARROW_ASSIGN_OR_RAISE(auto field, ref->GetOneOrNone(*in.type)); + auto descr = field ? ValueDescr{field->type(), in.shape} : ValueDescr::Scalar(null()); + return Expression{Parameter{*ref, std::move(descr)}}; + } + + auto bound_call = *CallNotNull(*this); + + ARROW_ASSIGN_OR_RAISE(bound_call.function, GetFunction(bound_call, exec_context)); + + for (auto&& argument : bound_call.arguments) { + ARROW_ASSIGN_OR_RAISE(argument, argument.Bind(in, exec_context)); + } + RETURN_NOT_OK(InsertImplicitCasts(&bound_call)); + + auto descrs = GetDescriptors(bound_call.arguments); + ARROW_ASSIGN_OR_RAISE(bound_call.kernel, bound_call.function->DispatchExact(descrs)); + + compute::KernelContext kernel_context(exec_context); + ARROW_ASSIGN_OR_RAISE(bound_call.kernel_state, + InitKernelState(bound_call, exec_context)); + kernel_context.SetState(bound_call.kernel_state.get()); + + ARROW_ASSIGN_OR_RAISE( + bound_call.descr, + bound_call.kernel->signature->out_type().Resolve(&kernel_context, descrs)); + + return Expression(std::move(bound_call)); +} + +Result<Expression> Expression::Bind(const Schema& in_schema, + compute::ExecContext* exec_context) const { + return Bind(ValueDescr::Array(struct_(in_schema.fields())), exec_context); +} + +Result<Datum> ExecuteScalarExpression(const Expression& expr, const Datum& input, + compute::ExecContext* exec_context) { + if (exec_context == nullptr) { + compute::ExecContext exec_context; + return ExecuteScalarExpression(expr, input, &exec_context); + } + + if (!expr.IsBound()) { + return Status::Invalid("Cannot Execute unbound expression."); + } + + if (!expr.IsScalarExpression()) { + return Status::Invalid( + "ExecuteScalarExpression cannot Execute non-scalar expression ", expr.ToString()); + } + + if (auto lit = expr.literal()) return *lit; + + if (auto ref = expr.field_ref()) { + ARROW_ASSIGN_OR_RAISE(Datum field, GetDatumField(*ref, input)); + + if (field.descr() != expr.descr()) { + // Refernced field was present but didn't have the expected type. + // Should we just error here? For now, pay dispatch cost and just cast. + ARROW_ASSIGN_OR_RAISE( + field, compute::Cast(field, expr.descr().type, compute::CastOptions::Safe(), + exec_context)); + } + + return field; + } + + auto call = CallNotNull(expr); + + std::vector<Datum> arguments(call->arguments.size()); + for (size_t i = 0; i < arguments.size(); ++i) { + ARROW_ASSIGN_OR_RAISE( + arguments[i], ExecuteScalarExpression(call->arguments[i], input, exec_context)); + } + + auto executor = compute::detail::KernelExecutor::MakeScalar(); + + compute::KernelContext kernel_context(exec_context); + kernel_context.SetState(call->kernel_state.get()); + + auto kernel = call->kernel; + auto descrs = GetDescriptors(arguments); + auto options = call->options.get(); + RETURN_NOT_OK(executor->Init(&kernel_context, {kernel, descrs, options})); + + auto listener = std::make_shared<compute::detail::DatumAccumulator>(); + RETURN_NOT_OK(executor->Execute(arguments, listener.get())); + return executor->WrapResults(arguments, listener->values()); +} + +std::array<std::pair<const Expression&, const Expression&>, 2> +ArgumentsAndFlippedArguments(const Expression::Call& call) { + DCHECK_EQ(call.arguments.size(), 2); + return {std::pair<const Expression&, const Expression&>{call.arguments[0], + call.arguments[1]}, + std::pair<const Expression&, const Expression&>{call.arguments[1], + call.arguments[0]}}; +} + +template <typename BinOp, typename It, + typename Out = typename std::iterator_traits<It>::value_type> +util::optional<Out> FoldLeft(It begin, It end, const BinOp& bin_op) { + if (begin == end) return util::nullopt; + + Out folded = std::move(*begin++); + while (begin != end) { + folded = bin_op(std::move(folded), std::move(*begin++)); + } + return folded; +} + +util::optional<compute::NullHandling::type> GetNullHandling( + const Expression::Call& call) { + if (call.function && call.function->kind() == compute::Function::SCALAR) { + return static_cast<const compute::ScalarKernel*>(call.kernel)->null_handling; + } + return util::nullopt; +} + +bool DefinitelyNotNull(const Expression& expr) { + DCHECK(expr.IsBound()); + + if (expr.literal()) { + return !expr.IsNullLiteral(); + } + + if (expr.field_ref()) return false; + + auto call = CallNotNull(expr); + if (auto null_handling = GetNullHandling(*call)) { + if (null_handling == compute::NullHandling::OUTPUT_NOT_NULL) { + return true; + } + if (null_handling == compute::NullHandling::INTERSECTION) { + return std::all_of(call->arguments.begin(), call->arguments.end(), + DefinitelyNotNull); + } + } + + return false; +} + +std::vector<FieldRef> FieldsInExpression(const Expression& expr) { + if (auto lit = expr.literal()) return {}; + + if (auto ref = expr.field_ref()) { + return {*ref}; + } + + std::vector<FieldRef> fields; + for (const Expression& arg : CallNotNull(expr)->arguments) { + auto argument_fields = FieldsInExpression(arg); + std::move(argument_fields.begin(), argument_fields.end(), std::back_inserter(fields)); + } + return fields; +} + +Result<Expression> FoldConstants(Expression expr) { + return Modify( + std::move(expr), [](Expression expr) { return expr; }, + [](Expression expr, ...) -> Result<Expression> { + auto call = CallNotNull(expr); + if (std::all_of(call->arguments.begin(), call->arguments.end(), + [](const Expression& argument) { return argument.literal(); })) { + // all arguments are literal; we can evaluate this subexpression *now* + static const Datum ignored_input; + ARROW_ASSIGN_OR_RAISE(Datum constant, + ExecuteScalarExpression(expr, ignored_input)); + + return literal(std::move(constant)); + } + + // XXX the following should probably be in a registry of passes instead + // of inline + + if (GetNullHandling(*call) == compute::NullHandling::INTERSECTION) { + // kernels which always produce intersected validity can be resolved + // to null *now* if any of their inputs is a null literal + for (const auto& argument : call->arguments) { + if (argument.IsNullLiteral()) { + return argument; + } + } + } + + if (call->function_name == "and_kleene") { + for (auto args : ArgumentsAndFlippedArguments(*call)) { + // true and x == x + if (args.first == literal(true)) return args.second; + + // false and x == false + if (args.first == literal(false)) return args.first; + + // x and x == x + if (args.first == args.second) return args.first; + } + return expr; + } + + if (call->function_name == "or_kleene") { + for (auto args : ArgumentsAndFlippedArguments(*call)) { + // false or x == x + if (args.first == literal(false)) return args.second; + + // true or x == true + if (args.first == literal(true)) return args.first; + + // x or x == x + if (args.first == args.second) return args.first; + } + return expr; + } + + return expr; + }); +} + +inline std::vector<Expression> GuaranteeConjunctionMembers( + const Expression& guaranteed_true_predicate) { + auto guarantee = guaranteed_true_predicate.call(); + if (!guarantee || guarantee->function_name != "and_kleene") { + return {guaranteed_true_predicate}; + } + return FlattenedAssociativeChain(guaranteed_true_predicate).fringe; +} + +// Conjunction members which are represented in known_values are erased from +// conjunction_members +Status ExtractKnownFieldValuesImpl( + std::vector<Expression>* conjunction_members, + std::unordered_map<FieldRef, Datum, FieldRef::Hash>* known_values) { + auto unconsumed_end = + std::partition(conjunction_members->begin(), conjunction_members->end(), + [](const Expression& expr) { + // search for an equality conditions between a field and a literal + auto call = expr.call(); + if (!call) return true; + + if (call->function_name == "equal") { + auto ref = call->arguments[0].field_ref(); + auto lit = call->arguments[1].literal(); + return !(ref && lit); Review comment: Ok, add this requirement to the docstring perhaps? ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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