mirror of
https://github.com/ClickHouse/ClickHouse.git
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258 lines
8.6 KiB
C++
258 lines
8.6 KiB
C++
#include <Functions/FunctionFactory.h>
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#include <Functions/FunctionIfBase.h>
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#include <Columns/ColumnNullable.h>
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#include <Columns/ColumnConst.h>
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#include <Columns/ColumnsNumber.h>
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#include <Interpreters/castColumn.h>
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#include <Common/typeid_cast.h>
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#include <Common/assert_cast.h>
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#include <DataTypes/DataTypeNullable.h>
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#include <DataTypes/getLeastSupertype.h>
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namespace DB
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{
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namespace ErrorCodes
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{
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extern const int ILLEGAL_TYPE_OF_ARGUMENT;
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extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
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}
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namespace
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{
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/// Function multiIf, which generalizes the function if.
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///
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/// Syntax: multiIf(cond_1, then_1, ..., cond_N, then_N, else)
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/// where N >= 1.
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///
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/// For all 1 <= i <= N, "cond_i" has type UInt8.
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/// Types of all the branches "then_i" and "else" have a common type.
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///
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/// Additionally the arguments, conditions or branches, support nullable types
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/// and the NULL value, with a NULL condition treated as false.
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class FunctionMultiIf final : public FunctionIfBase</*null_is_false=*/true>
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{
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public:
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static constexpr auto name = "multiIf";
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static FunctionPtr create(const Context &) { return std::make_shared<FunctionMultiIf>(); }
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String getName() const override { return name; }
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bool isVariadic() const override { return true; }
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size_t getNumberOfArguments() const override { return 0; }
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bool useDefaultImplementationForNulls() const override { return false; }
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ColumnNumbers getArgumentsThatDontImplyNullableReturnType(size_t number_of_arguments) const override
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{
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ColumnNumbers args;
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for (size_t i = 0; i + 1 < number_of_arguments; i += 2)
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args.push_back(i);
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return args;
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}
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DataTypePtr getReturnTypeImpl(const DataTypes & args) const override
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{
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/// Arguments are the following: cond1, then1, cond2, then2, ... condN, thenN, else.
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auto for_conditions = [&args](auto && f)
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{
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size_t conditions_end = args.size() - 1;
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for (size_t i = 0; i < conditions_end; i += 2)
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f(args[i]);
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};
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auto for_branches = [&args](auto && f)
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{
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size_t branches_end = args.size();
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for (size_t i = 1; i < branches_end; i += 2)
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f(args[i]);
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f(args.back());
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};
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if (!(args.size() >= 3 && args.size() % 2 == 1))
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throw Exception{"Invalid number of arguments for function " + getName(),
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ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH};
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for_conditions([&](const DataTypePtr & arg)
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{
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const IDataType * nested_type;
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if (arg->isNullable())
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{
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if (arg->onlyNull())
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return;
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const DataTypeNullable & nullable_type = static_cast<const DataTypeNullable &>(*arg);
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nested_type = nullable_type.getNestedType().get();
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}
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else
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{
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nested_type = arg.get();
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}
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if (!WhichDataType(nested_type).isUInt8())
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throw Exception{"Illegal type " + arg->getName() + " of argument (condition) "
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"of function " + getName() + ". Must be UInt8.",
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ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT};
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});
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DataTypes types_of_branches;
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types_of_branches.reserve(args.size() / 2 + 1);
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for_branches([&](const DataTypePtr & arg)
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{
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types_of_branches.emplace_back(arg);
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});
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return getLeastSupertype(types_of_branches);
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}
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ColumnPtr executeImpl(const ColumnsWithTypeAndName & args, const DataTypePtr & result_type, size_t input_rows_count) const override
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{
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/** We will gather values from columns in branches to result column,
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* depending on values of conditions.
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*/
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struct Instruction
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{
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const IColumn * condition = nullptr;
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const IColumn * source = nullptr;
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bool condition_always_true = false;
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bool condition_is_nullable = false;
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bool source_is_constant = false;
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};
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std::vector<Instruction> instructions;
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instructions.reserve(args.size() / 2 + 1);
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Columns converted_columns_holder;
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converted_columns_holder.reserve(instructions.size());
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const DataTypePtr & return_type = result_type;
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for (size_t i = 0; i < args.size(); i += 2)
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{
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Instruction instruction;
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size_t source_idx = i + 1;
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bool last_else_branch = source_idx == args.size();
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if (last_else_branch)
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{
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/// The last, "else" branch can be treated as a branch with always true condition "else if (true)".
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--source_idx;
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instruction.condition_always_true = true;
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}
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else
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{
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const ColumnWithTypeAndName & cond_col = args[i];
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/// We skip branches that are always false.
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/// If we encounter a branch that is always true, we can finish.
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if (cond_col.column->onlyNull())
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continue;
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if (const auto * column_const = checkAndGetColumn<ColumnConst>(*cond_col.column))
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{
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Field value = column_const->getField();
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if (value.isNull())
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continue;
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if (value.get<UInt64>() == 0)
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continue;
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instruction.condition_always_true = true;
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}
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else
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{
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if (isColumnNullable(*cond_col.column))
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instruction.condition_is_nullable = true;
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instruction.condition = cond_col.column.get();
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}
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}
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const ColumnWithTypeAndName & source_col = args[source_idx];
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if (source_col.type->equals(*return_type))
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{
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instruction.source = source_col.column.get();
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}
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else
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{
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/// Cast all columns to result type.
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converted_columns_holder.emplace_back(castColumn(source_col, return_type));
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instruction.source = converted_columns_holder.back().get();
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}
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if (instruction.source && isColumnConst(*instruction.source))
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instruction.source_is_constant = true;
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instructions.emplace_back(std::move(instruction));
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if (instructions.back().condition_always_true)
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break;
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}
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MutableColumnPtr res = return_type->createColumn();
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/// Special case if first instruction condition is always true and source is constant
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if (instructions.size() == 1 && instructions.front().source_is_constant
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&& instructions.front().condition_always_true)
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{
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auto & instruction = instructions.front();
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res->insertFrom(assert_cast<const ColumnConst &>(*instruction.source).getDataColumn(), 0);
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return ColumnConst::create(std::move(res), instruction.source->size());
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}
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size_t rows = input_rows_count;
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for (size_t i = 0; i < rows; ++i)
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{
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for (const auto & instruction : instructions)
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{
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bool insert = false;
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if (instruction.condition_always_true)
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insert = true;
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else if (!instruction.condition_is_nullable)
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insert = assert_cast<const ColumnUInt8 &>(*instruction.condition).getData()[i];
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else
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{
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const ColumnNullable & condition_nullable = assert_cast<const ColumnNullable &>(*instruction.condition);
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const ColumnUInt8 & condition_nested = assert_cast<const ColumnUInt8 &>(condition_nullable.getNestedColumn());
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const NullMap & condition_null_map = condition_nullable.getNullMapData();
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insert = !condition_null_map[i] && condition_nested.getData()[i];
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}
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if (insert)
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{
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if (!instruction.source_is_constant)
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res->insertFrom(*instruction.source, i);
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else
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res->insertFrom(assert_cast<const ColumnConst &>(*instruction.source).getDataColumn(), 0);
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break;
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}
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}
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}
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return res;
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}
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};
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}
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void registerFunctionMultiIf(FunctionFactory & factory)
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{
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factory.registerFunction<FunctionMultiIf>();
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/// These are obsolete function names.
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factory.registerFunction<FunctionMultiIf>("caseWithoutExpr");
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factory.registerFunction<FunctionMultiIf>("caseWithoutExpression");
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}
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}
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