feat: implement shiftLeft function push down (#5495)

close #5099
pingcap · Aug 4, 2022 · e17ef39 · e17ef39
1 parent 0bafed9
commit e17ef39
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Showing 5 changed files with 313 additions and 2 deletions.
diff --git a/dbms/src/Flash/Coprocessor/DAGExpressionAnalyzerHelper.cpp b/dbms/src/Flash/Coprocessor/DAGExpressionAnalyzerHelper.cpp
@@ -450,6 +450,7 @@ DAGExpressionAnalyzerHelper::FunctionBuilderMap DAGExpressionAnalyzerHelper::fun
  {"bitOr", DAGExpressionAnalyzerHelper::buildBitwiseFunction},
  {"bitXor", DAGExpressionAnalyzerHelper::buildBitwiseFunction},
  {"bitNot", DAGExpressionAnalyzerHelper::buildBitwiseFunction},
+ {"bitShiftLeft", DAGExpressionAnalyzerHelper::buildBitwiseFunction},
  {"bitShiftRight", DAGExpressionAnalyzerHelper::buildBitwiseFunction},
  {"leftUTF8", DAGExpressionAnalyzerHelper::buildLeftUTF8Function},
  {"date_add", DAGExpressionAnalyzerHelper::buildDateAddOrSubFunction<DateAdd>},

diff --git a/dbms/src/Flash/Coprocessor/DAGUtils.cpp b/dbms/src/Flash/Coprocessor/DAGUtils.cpp
@@ -331,7 +331,7 @@ const std::unordered_map<tipb::ScalarFuncSig, String> scalar_func_map({
  {tipb::ScalarFuncSig::DecimalIsFalse, "isFalse"},
  {tipb::ScalarFuncSig::DecimalIsFalseWithNull, "isFalseWithNull"},
 
- //{tipb::ScalarFuncSig::LeftShift, "cast"},
+ {tipb::ScalarFuncSig::LeftShift, "bitShiftLeft"},
  {tipb::ScalarFuncSig::RightShift, "bitShiftRight"},
 
  //{tipb::ScalarFuncSig::BitCount, "cast"},

diff --git a/dbms/src/Functions/bitShiftLeft.cpp b/dbms/src/Functions/bitShiftLeft.cpp
@@ -29,7 +29,18 @@ struct BitShiftLeftImpl<A, B, false>
  template <typename Result = ResultType>
  static Result apply(A a, B b)
  {
- return static_cast<Result>(a) << static_cast<Result>(b);
+ // It is an undefined behavior for shift operation in c++ that the right operand is negative or greater than
+ // or equal to the number of digits of the bits in the (promoted) left operand.
+ // See https://en.cppreference.com/w/cpp/language/operator_arithmetic for details.
+ if (static_cast<Result>(b) >= std::numeric_limits<decltype(static_cast<Result>(a))>::digits)
+ {
+ return static_cast<Result>(0);
+ }
+ // Note that we do not consider the case that the right operand is negative,
+ // since other types will all be cast to uint64 before shift operation
+ // according to DAGExpressionAnalyzerHelper::buildBitwiseFunction.
+ // Therefore, we simply suppress clang-tidy checking here.
+ return static_cast<Result>(a) << static_cast<Result>(b); // NOLINT(clang-analyzer-core.UndefinedBinaryOperatorResult)
  }
  template <typename Result = ResultType>
  static Result apply(A, B, UInt8 &)