Implemented function NOW() (#1377)

* Added conversion str to int * templated function for toNumeric, add declaration to NaryExpression.h * str to num for SparqlExpression implemented + added test * Update src/engine/sparqlExpressions/StringExpressions.cpp Co-authored-by: Johannes Kalmbach <joka921@users.noreply.github.com> * Update src/engine/sparqlExpressions/StringExpressions.cpp Co-authored-by: Johannes Kalmbach <joka921@users.noreply.github.com> * Update src/engine/sparqlExpressions/StringExpressions.cpp Co-authored-by: Johannes Kalmbach <joka921@users.noreply.github.com> * Update src/engine/sparqlExpressions/StringExpressions.cpp Co-authored-by: Johannes Kalmbach <joka921@users.noreply.github.com> * using now absl::from_chars() and stripping whitespaces for string to number conv. * added new functions to processIriFuntionCall() (for string to number) * renaming to: toIntExpression and toDoubleExpression for later more general implementation * made format (clang-format-16) * Update src/parser/sparqlParser/SparqlQleverVisitor.cpp Co-authored-by: Johannes Kalmbach <joka921@users.noreply.github.com> * Update src/parser/sparqlParser/SparqlQleverVisitor.cpp Co-authored-by: Johannes Kalmbach <joka921@users.noreply.github.com> * renaming in NaryExpression.h for accordance with other function, adding correct prefix in Constants.h * added test coverage for function calls makeIntExpression and make DoubleExpression * toNumeric has now correct behavior and uses absl::from_chars() and std::from_chars() * made clang-format for NaryExpressionImpl.h * first implementation NOW() expression * fix spelling error * pass by reference * changes w.r.t. pull-request comments * last changes for #1377 --------- Co-authored-by: Johannes Kalmbach <joka921@users.noreply.github.com>
ad-freiburg · Jun 19, 2024 · 1be8381 · 1be8381
1 parent f9e730c
commit 1be8381
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diff --git a/src/engine/sparqlExpressions/NowDatetimeExpression.h b/src/engine/sparqlExpressions/NowDatetimeExpression.h
@@ -0,0 +1,38 @@
+//  Copyright 2024, University of Freiburg,
+//                  Chair of Algorithms and Data Structures
+//  Author: Hannes Baumann <baumannh@informatik.uni-freiburg.de>
+
+#include "engine/sparqlExpressions/SparqlExpression.h"
+#include "util/ChunkedForLoop.h"
+#include "util/Date.h"
+#include "util/Random.h"
+
+namespace sparqlExpression {
+
+// The expression `NOW()` is evaluated within NowDatetimeExpression.h.
+// `NowDatetimeExpression` has to be explicitly constructed from a
+// `date-formatted string`, which is for all evaluations within a Sparql
+// query the same.
+class NowDatetimeExpression : public SparqlExpression {
+ private:
+  DateOrLargeYear date_;
+
+ public:
+  explicit NowDatetimeExpression(const std::string& dateTimeFormat)
+      : date_(DateOrLargeYear::parseXsdDatetime(dateTimeFormat)) {}
+
+  std::string getCacheKey(
+      [[maybe_unused]] const VariableToColumnMap& varColMap) const override {
+    return absl::StrCat("NOW ", date_.toBits());
+  }
+
+  ExpressionResult evaluate(
+      [[maybe_unused]] EvaluationContext* context) const override {
+    return Id::makeFromDate(date_);
+  }
+
+ private:
+  std::span<SparqlExpression::Ptr> childrenImpl() override { return {}; }
+};
+
+}  // namespace sparqlExpression
diff --git a/src/parser/sparqlParser/SparqlQleverVisitor.cpp b/src/parser/sparqlParser/SparqlQleverVisitor.cpp
@@ -13,16 +13,20 @@
 #include <string>
 #include <vector>
 
+#include "absl/time/time.h"
+#include "engine/sparqlExpressions/GroupConcatExpression.h"
 #include "engine/sparqlExpressions/LangExpression.h"
+#include "engine/sparqlExpressions/LiteralExpression.h"
+#include "engine/sparqlExpressions/NowDatetimeExpression.h"
 #include "engine/sparqlExpressions/RandomExpression.h"
 #include "engine/sparqlExpressions/RegexExpression.h"
 #include "engine/sparqlExpressions/RelationalExpressions.h"
+#include "engine/sparqlExpressions/SampleExpression.h"
 #include "engine/sparqlExpressions/UuidExpressions.h"
 #include "parser/SparqlParser.h"
 #include "parser/TokenizerCtre.h"
 #include "parser/TurtleParser.h"
 #include "parser/data/Variable.h"
-#include "util/OnDestructionDontThrowDuringStackUnwinding.h"
 #include "util/StringUtils.h"
 #include "util/TransparentFunctors.h"
 #include "util/antlr/GenerateAntlrExceptionMetadata.h"
@@ -55,6 +59,12 @@ std::string Visitor::getOriginalInputForContext(
       ad_utility::getUTF8Substring(fullInput, posBeg, posEnd - posBeg + 1)};
 }
 
+// _____________________________________________________________________________
+std::string Visitor::currentTimeAsXsdString() {
+  return absl::FormatTime("%Y-%m-%dT%H:%M:%E3S%Ez", absl::Now(),
+                          absl::LocalTimeZone());
+}
+
 // ___________________________________________________________________________
 ExpressionPtr Visitor::processIriFunctionCall(
     const TripleComponent::Iri& iri, std::vector<ExpressionPtr> argList,
@@ -2001,6 +2011,9 @@ ExpressionPtr Visitor::visit([[maybe_unused]] Parser::BuiltInCallContext* ctx) {
     return createUnary(&makeDayExpression);
   } else if (functionName == "tz") {
     return createUnary(&makeTimezoneStrExpression);
+  } else if (functionName == "now") {
+    AD_CONTRACT_CHECK(argList.empty());
+    return std::make_unique<NowDatetimeExpression>(startTime_);
   } else if (functionName == "hours") {
     return createUnary(&makeHoursExpression);
   } else if (functionName == "minutes") {

diff --git a/src/parser/sparqlParser/SparqlQleverVisitor.h b/src/parser/sparqlParser/SparqlQleverVisitor.h
@@ -9,26 +9,11 @@
 #include <antlr4-runtime.h>
 
 #include "engine/sparqlExpressions/AggregateExpression.h"
-#include "engine/sparqlExpressions/GroupConcatExpression.h"
-#include "engine/sparqlExpressions/LiteralExpression.h"
 #include "engine/sparqlExpressions/NaryExpression.h"
-#include "engine/sparqlExpressions/SampleExpression.h"
-#include "engine/sparqlExpressions/SparqlExpressionPimpl.h"
-#include "parser/Alias.h"
-#include "parser/ConstructClause.h"
-#include "parser/ParsedQuery.h"
-#include "parser/RdfEscaping.h"
-#include "parser/data/BlankNode.h"
 #include "parser/data/GraphRef.h"
-#include "parser/data/Iri.h"
-#include "parser/data/SolutionModifiers.h"
-#include "parser/data/Types.h"
 #undef EOF
 #include "parser/sparqlParser/generated/SparqlAutomaticVisitor.h"
 #define EOF std::char_traits<char>::eof()
-#include "util/HashMap.h"
-#include "util/OverloadCallOperator.h"
-#include "util/StringUtils.h"
 
 template <typename T>
 class Reversed {
@@ -472,6 +457,14 @@ class SparqlQleverVisitor {
   string visit(Parser::PnameNsContext* ctx);
 
  private:
+  // Helper to assign variable `startTime_` a correctly formatted time string.
+  static std::string currentTimeAsXsdString();
+
+  // Member starTime_ is needed for the NOW expression. All calls within
+  // the query execution reference it. The underlying date time format is e.g.:
+  // 2011-01-10T14:45:13.815-05:00
+  std::string startTime_ = currentTimeAsXsdString();
+
   template <typename Visitor, typename Ctx>
   static constexpr bool voidWhenVisited =
       std::is_void_v<decltype(std::declval<Visitor&>().visit(

diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
@@ -294,6 +294,8 @@ addLinkAndDiscoverTest(ExceptionTest)
 
 addLinkAndDiscoverTestSerial(RandomExpressionTest index)
 
+addLinkAndDiscoverTestSerial(NowDatetimeExpressionTest index)
+
 addLinkAndDiscoverTestSerial(SortTest engine)
 
 addLinkAndDiscoverTestSerial(OrderByTest engine)

diff --git a/test/NowDatetimeExpressionTest.cpp b/test/NowDatetimeExpressionTest.cpp
@@ -0,0 +1,57 @@
+//  Copyright 2024, University of Freiburg,
+//                  Chair of Algorithms and Data Structures
+//  Author: Hannes Baumann <baumannh@informatik.uni-freiburg.de>
+
+#include "./SparqlExpressionTestHelpers.h"
+#include "engine/sparqlExpressions/NowDatetimeExpression.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+using namespace sparqlExpression;
+
+TEST(NowDatetimeExpression, nowExpressionEvaluate) {
+  std::string strDate = "2011-01-10T14:45:13.815-05:00";
+  TestContext testContext{};
+  auto& evaluationContext = testContext.context;
+
+  // technically the evaluation context isn't necessary.
+  evaluationContext._beginIndex = 43;
+  evaluationContext._endIndex = 1044;
+
+  // The result should hold an ID (from Date) given that NOW() should return by
+  // definition a xsd:dateTime: "2011-01-10T14:45:13.815-05:00"^^xsd:dateTime
+  auto resultAsVariant =
+      NowDatetimeExpression{strDate}.evaluate(&evaluationContext);
+  ASSERT_TRUE(std::holds_alternative<Id>(resultAsVariant));
+  const auto& resultDate = std::get<Id>(resultAsVariant);
+
+  DateOrLargeYear dateNowTest =
+      DateOrLargeYear(DateOrLargeYear::parseXsdDatetime(strDate));
+
+  ASSERT_EQ(resultDate.getDatatype(), Datatype::Date);
+  ASSERT_EQ(resultDate.getDate(), dateNowTest);
+
+  evaluationContext._isPartOfGroupBy = true;
+  auto resultAsVariant2 =
+      NowDatetimeExpression{strDate}.evaluate(&evaluationContext);
+  ASSERT_TRUE(std::holds_alternative<Id>(resultAsVariant2));
+  DateOrLargeYear singleDateNow = std::get<Id>(resultAsVariant2).getDate();
+  ASSERT_EQ(singleDateNow, dateNowTest);
+}
+
+TEST(NowDatetimeExpression, getCacheKeyNowExpression) {
+  std::string strDate1 = "2011-01-10T14:45:13.815-05:00";
+  std::string strDate2 = "2024-06-18T12:16:33.815-06:00";
+  NowDatetimeExpression dateNow1(strDate1);
+  NowDatetimeExpression dateNow2(strDate2);
+  ASSERT_TRUE(dateNow1.getUnaggregatedVariables().empty());
+  auto cacheKey1 = dateNow1.getCacheKey({});
+  ASSERT_THAT(cacheKey1, ::testing::StartsWith("NOW "));
+  ASSERT_EQ(cacheKey1, dateNow1.getCacheKey({}));
+  // Given that these use the same date-time string the key should be equal.
+  ASSERT_EQ(cacheKey1, NowDatetimeExpression{strDate1}.getCacheKey({}));
+  // Given that dateNow1 and dateNow2 are constructed from different date-time
+  // strings, it should be rather unlikely that their cache-keys are equal.
+  auto cacheKey2 = dateNow2.getCacheKey({});
+  ASSERT_NE(cacheKey1, cacheKey2);
+}
diff --git a/test/SparqlAntlrParserTest.cpp b/test/SparqlAntlrParserTest.cpp
@@ -18,6 +18,7 @@
 #include "SparqlAntlrParserTestHelpers.h"
 #include "engine/sparqlExpressions/LangExpression.h"
 #include "engine/sparqlExpressions/LiteralExpression.h"
+#include "engine/sparqlExpressions/NowDatetimeExpression.h"
 #include "engine/sparqlExpressions/RandomExpression.h"
 #include "engine/sparqlExpressions/RegexExpression.h"
 #include "engine/sparqlExpressions/UuidExpressions.h"
@@ -1385,6 +1386,7 @@ TEST(SparqlParser, builtInCall) {
   expectBuiltInCall("month(?x)", matchUnary(&makeMonthExpression));
   expectBuiltInCall("tz(?x)", matchUnary(&makeTimezoneStrExpression));
   expectBuiltInCall("day(?x)", matchUnary(&makeDayExpression));
+  expectBuiltInCall("NOW()", matchPtr<NowDatetimeExpression>());
   expectBuiltInCall("hours(?x)", matchUnary(&makeHoursExpression));
   expectBuiltInCall("minutes(?x)", matchUnary(&makeMinutesExpression));
   expectBuiltInCall("seconds(?x)", matchUnary(&makeSecondsExpression));