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Merge pull request ClickHouse#90567 from ClickHouse/backport/25.8/88441
Backport ClickHouse#88441 to 25.8: Backporting function firstNonDefault
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‎src/Functions/firstNonDefault.cpp‎

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#include <Columns/IColumn.h>
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#include <DataTypes/getLeastSupertype.h>
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#include <Functions/FunctionFactory.h>
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#include <Functions/IFunction.h>
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#include <Interpreters/castColumn.h>
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#include <Interpreters/Context_fwd.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 LOGICAL_ERROR;
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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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/// Implements the function which takes a set of arguments and
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/// returns the value of the leftmost non-falsey argument.
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/// If all arguments are falsey, returns the default value for the result type.
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/// Result type is the supertype of all arguments.
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class FunctionFirstNonDefault : public IFunction
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{
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public:
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static constexpr auto name = "firstNonDefault";
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static FunctionPtr create(ContextPtr)
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{
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return std::make_shared<FunctionFirstNonDefault>();
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}
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FunctionFirstNonDefault() = default;
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String getName() const override { return name; }
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bool useDefaultImplementationForConstants() const override { return true; }
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bool useDefaultImplementationForLowCardinalityColumns() const override { return false; }
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bool useDefaultImplementationForNulls() const override { return false; }
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bool isVariadic() const override { return true; }
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bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return false; }
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size_t getNumberOfArguments() const override { return 0; }
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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)
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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 & arguments) const override
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{
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if (arguments.empty())
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throw Exception(ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH,
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"Function {} requires at least one argument", getName());
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size_t max_args = 1024;
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if (arguments.size() > max_args)
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throw Exception(ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH,
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"Function {} requires at most {} arguments, got {}", getName(), max_args, arguments.size());
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if (arguments.size() == 1)
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return arguments[0];
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return getLeastSupertype(arguments);
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}
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ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr & result_type, size_t input_rows_count) const override
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{
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if (arguments.size() == 1)
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return arguments[0].column;
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size_t num_columns = arguments.size();
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auto result_col = result_type->createColumn();
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result_col->reserve(input_rows_count);
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/// Cast all arguments to the result type
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/// Use this columns to insert values into the result column
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std::vector<ColumnPtr> casted_columns;
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casted_columns.reserve(num_columns);
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for (const auto & arg : arguments)
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{
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auto casted_column = castColumn(arg, result_type);
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casted_column = casted_column->convertToFullColumnIfConst();
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casted_column = casted_column->convertToFullColumnIfSparse();
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if (casted_column->getDataType() != result_col->getDataType())
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{
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throw Exception(ErrorCodes::LOGICAL_ERROR,
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"All arguments must cast to the same type, got {} and {} for result type {}",
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casted_column->dumpStructure(), result_col->dumpStructure(), result_type->getName());
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}
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casted_columns.push_back(std::move(casted_column));
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}
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for (size_t row = 0; row < input_rows_count; ++row)
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{
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bool found = false;
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/// Check each argument for truthiness
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for (size_t arg_idx = 0; !found && arg_idx < num_columns; ++arg_idx)
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{
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/// A value is considered "falsey" if it's NULL or the default value for its type
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/// For example:
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/// - for numeric types, the default is 0
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/// - for strings, the default is ''
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/// - for arrays, the default is []
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if (!arguments[arg_idx].column->isDefaultAt(row))
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{
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/// Found a truthy value, insert it into the result
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result_col->insertFrom(*casted_columns[arg_idx], row);
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found = true;
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}
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}
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if (!found)
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result_col->insertDefault();
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}
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return result_col;
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}
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};
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}
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REGISTER_FUNCTION(FirstNonDefault)
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{
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FunctionDocumentation doc;
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doc.description = "Returns the first non-default value from a set of arguments";
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doc.arguments = {
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{"arg1", "The first argument to check"},
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{"arg2", "The second argument to check"},
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{"...", "Additional arguments to check"},
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};
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doc.returned_value = FunctionDocumentation::ReturnedValue{"Result type is the supertype of all arguments", {}};
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doc.examples = {
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{"integers", "SELECT firstNonDefault(0, 1, 2)", "1"},
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{"strings", "SELECT firstNonDefault('', 'hello', 'world')", "'hello'"},
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{"nulls", "SELECT firstNonDefault(NULL, 0 :: UInt8, 1 :: UInt8)", "1"},
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{"nullable zero", "SELECT firstNonDefault(NULL, 0 :: Nullable(UInt8), 1 :: Nullable(UInt8))", "0"},
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};
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doc.category = {FunctionDocumentation::Category::Null};
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doc.introduced_in = {25, 9};
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factory.registerFunction<FunctionFirstNonDefault>(doc, FunctionFactory::Case::Insensitive);
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}
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}

‎tests/queries/0_stateless/03522_function_first_non_default.reference‎

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43
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0
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0
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\N
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true
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[1,2,3]
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foo Nullable(String)
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42 UInt32
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42 Int32
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42 UInt128
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42 Int128
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42 Int16
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42 Int64
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42.5 Float64
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42 Float64
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0 Nullable(Int32)
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42 Nullable(Int32)
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0 String
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0 String
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[0] Array(Int32)
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[''] Array(String)
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42 Nullable(UInt8)
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0 Nullable(String)
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\N Nullable(Nothing)
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0 UInt8
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String
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[] Array(UInt8)
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0
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1
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2
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0 0 0 Nullable(Int32)
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0 0 0 Nullable(Int32)
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0 0 0 Nullable(Int32)
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0 2 0 Nullable(Int32)
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0 \N 0 Nullable(Int32)
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1 0 1 Nullable(Int32)
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\N 0 0 Nullable(Int32)
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\N \N \N Nullable(Int32)
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Nullable(String)
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Nullable(String)
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Nullable(String)
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Nullable(String)
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Nullable(String)
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hello hello Nullable(String)
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\N default Nullable(String)
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\N default Nullable(String)
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[] [99,100] Array(Int32)
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[] [99,100] Array(Int32)
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[] [99,100] Array(Int32)
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[] [99,100] Array(Int32)
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[] [99,100] Array(Int32)
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[] [99,100] Array(Int32)
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[] [99,100] Array(Int32)
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[1,2,3] [1,2,3] Array(Int32)
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0 0 0 Nullable(Int64)
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0 0 0 Nullable(Int64)
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0 0 0 Nullable(Int64)
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0 2 2 Nullable(Int64)
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0 \N \N Nullable(Int64)
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1 0 1 Nullable(Int64)
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\N 0 \N Nullable(Int64)
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\N \N \N Nullable(Int64)
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0 0 42 0 0
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0 0 42 0 0
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0 0 42 0 0
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0 2 42 0 0
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0 \N 42 0 0
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1 0 42 1 1
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\N 0 42 0 0
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\N \N 42 \N \N

‎tests/queries/0_stateless/03522_function_first_non_default.sql‎

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SELECT firstNonDefault(NULL, 0, 43, 256) AS result;
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SELECT firstNonDefault(NULL :: Nullable(UInt8), 0 :: Nullable(UInt8), 42 :: UInt8) AS result;
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SELECT firstNonDefault('', '0', 'hello') AS result;
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SELECT firstNonDefault(NULL::Nullable(UInt8), 0::UInt8) AS result;
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SELECT firstNonDefault(false, true) AS result;
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SELECT firstNonDefault([] :: Array(UInt8), [1, 2, 3] :: Array(UInt8)) AS result;
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SELECT firstNonDefault(NULL::Nullable(String), ''::String, 'foo') as result, toTypeName(result);
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SELECT firstNonDefault(0::UInt8, 0::UInt16, 42::UInt32) AS result, toTypeName(result);
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SELECT firstNonDefault(0::Int8, 0::Int16, 42::Int32) AS result, toTypeName(result);
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SELECT firstNonDefault(0::UInt32, 0::UInt64, 42::UInt128) AS result, toTypeName(result);
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SELECT firstNonDefault(0::Int128, 0::Int128, 42::Int128) AS result, toTypeName(result);
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SELECT firstNonDefault(0::UInt8, 0::Int8, 42::Int16) AS result, toTypeName(result);
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SELECT firstNonDefault(0::Int64, 0::Int64, 42::Int64) AS result, toTypeName(result);
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SELECT firstNonDefault(0.0::Float32, 0.0::Float64, 42.5::Float64) AS result, toTypeName(result);
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SELECT firstNonDefault(0::Float64, 0.0::Float64, 42.0::Float64) AS result, toTypeName(result);
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SELECT firstNonDefault(NULL::Nullable(Int32), 0::Nullable(Int32), 42::Nullable(Int32)) AS result, toTypeName(result);
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SELECT firstNonDefault(NULL, 0::Int32, 42::Nullable(Int32)) AS result, toTypeName(result);
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SELECT firstNonDefault(''::String, '0'::String, 'hello'::String) AS result, toTypeName(result);
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SELECT firstNonDefault(''::FixedString(5), '0'::String, 'hello'::String) AS result, toTypeName(result);
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SELECT firstNonDefault([]::Array(Int32), [0]::Array(Int32), [1, 2, 3]::Array(Int32)) AS result, toTypeName(result);
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SELECT firstNonDefault([]::Array(String), ['']::Array(String), ['hello']::Array(String)) AS result, toTypeName(result);
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SELECT firstNonDefault(NULL::Nullable(UInt8), 0::UInt8, 42::UInt8, 100::UInt8) AS result, toTypeName(result);
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SELECT firstNonDefault(NULL::Nullable(String), ''::String, '0'::String, 'hello'::String) AS result, toTypeName(result);
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SELECT firstNonDefault(NULL) AS result, toTypeName(result);
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SELECT firstNonDefault(0) AS result, toTypeName(result);
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SELECT firstNonDefault(''::String) AS result, toTypeName(result);
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SELECT firstNonDefault([]::Array(UInt8)) AS result, toTypeName(result);
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SELECT firstNonDefault(); -- { serverError NUMBER_OF_ARGUMENTS_DOESNT_MATCH }
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SELECT firstNonDefault(0, 'hello'); -- { serverError NO_COMMON_TYPE }
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SELECT firstNonDefault([]::Array(UInt8), 42); -- { serverError NO_COMMON_TYPE }
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SELECT firstNonDefault([]::Array(UInt8), 'hello'); -- { serverError NO_COMMON_TYPE }
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SELECT firstNonDefault(0::UInt64, 1::Int64); -- { serverError NO_COMMON_TYPE }
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SELECT firstNonDefault(NULL::Nullable(Array(UInt8)), []::Array(UInt8)); -- { serverError ILLEGAL_TYPE_OF_ARGUMENT }
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SELECT firstNonDefault(
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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number
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) FROM numbers(3);
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DROP TABLE IF EXISTS test_first_truthy;
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CREATE TABLE test_first_truthy
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(
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a Nullable(Int32),
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b Nullable(Int32),
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c Nullable(String),
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d Array(Int32)
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) ENGINE = Memory;
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INSERT INTO test_first_truthy VALUES
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(NULL, 0, NULL, []),
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(0, NULL, '', []),
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(NULL, NULL, NULL, []),
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(0, 0, '', []),
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(1, 0, '', []),
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(0, 2, '', []),
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(0, 0, 'hello', []),
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(0, 0, '', [1, 2, 3]);
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SELECT
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a, b,
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firstNonDefault(a, b) AS result,
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toTypeName(firstNonDefault(a, b)) AS type
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FROM test_first_truthy
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ORDER BY ALL;
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SELECT
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c,
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firstNonDefault(c, 'default'::String) AS result,
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toTypeName(firstNonDefault(c, 'default'::String)) AS type
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FROM test_first_truthy
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ORDER BY ALL;
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SELECT
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d,
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firstNonDefault(d, [99, 100]::Array(Int32)) AS result,
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toTypeName(firstNonDefault(d, [99, 100]::Array(Int32))) AS type
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FROM test_first_truthy
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ORDER BY length(result);
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SELECT
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a, b,
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firstNonDefault(a + b, a * b, a - b) AS result,
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toTypeName(firstNonDefault(a + b, a * b, a - b)) AS type
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FROM test_first_truthy
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ORDER BY ALL;
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SELECT
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a, b,
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firstNonDefault(42, a, b) AS result1,
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firstNonDefault(0, a, b) AS result2,
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firstNonDefault(NULL, a, b) AS result3
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FROM test_first_truthy
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ORDER BY ALL;
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DROP TABLE test_first_truthy;

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