ClickHouse/src/Functions/sleep.h

#pragma once
#include <unistd.h>
#include <Functions/IFunction.h>
#include <Functions/FunctionHelpers.h>
#include <Columns/ColumnConst.h>
#include <DataTypes/DataTypesNumber.h>
#include <Common/FieldVisitorConvertToNumber.h>
#include <Common/ProfileEvents.h>
#include <Common/assert_cast.h>
#include <base/sleep.h>
#include <IO/WriteHelpers.h>
#include <Interpreters/Context.h>


namespace ProfileEvents
{
extern const Event SleepFunctionCalls;
extern const Event SleepFunctionMicroseconds;
}

namespace DB
{

namespace ErrorCodes
{
    extern const int ILLEGAL_TYPE_OF_ARGUMENT;
    extern const int TOO_SLOW;
    extern const int ILLEGAL_COLUMN;
    extern const int BAD_ARGUMENTS;
}

/** sleep(seconds) - the specified number of seconds sleeps each columns.
  */

enum class FunctionSleepVariant
{
    PerBlock,
    PerRow
};

template <FunctionSleepVariant variant>
class FunctionSleep : public IFunction
{
private:
    UInt64 max_microseconds;
public:
    static constexpr auto name = variant == FunctionSleepVariant::PerBlock ? "sleep" : "sleepEachRow";
    static FunctionPtr create(ContextPtr context)
    {
        return std::make_shared<FunctionSleep<variant>>(context->getSettingsRef().function_sleep_max_microseconds_per_block);
    }

    FunctionSleep(UInt64 max_microseconds_) : max_microseconds(max_microseconds_)
    {
    }

    /// Get the name of the function.
    String getName() const override
    {
        return name;
    }

    /// Do not sleep during query analysis.
    bool isSuitableForConstantFolding() const override
    {
        return false;
    }

    size_t getNumberOfArguments() const override
    {
        return 1;
    }

    bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return true; }

    DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
    {
        WhichDataType which(arguments[0]);

        if (!which.isFloat()
            && !which.isNativeUInt())
            throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT, "Illegal type {} of argument of function {}, expected Float64",
                arguments[0]->getName(), getName());

        return std::make_shared<DataTypeUInt8>();
    }
    ColumnPtr executeImplDryRun(const ColumnsWithTypeAndName & arguments, const DataTypePtr & result_type, size_t /*input_rows_count*/) const override
    {
        return execute(arguments, result_type, true);
    }

    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr & result_type, size_t /*input_rows_count*/) const override
    {
        return execute(arguments, result_type, false);
    }

    ColumnPtr execute(const ColumnsWithTypeAndName & arguments, const DataTypePtr & result_type, bool dry_run) const
    {
        const IColumn * col = arguments[0].column.get();

        if (!isColumnConst(*col))
            throw Exception(ErrorCodes::ILLEGAL_COLUMN, "The argument of function {} must be constant.", getName());

        Float64 seconds = applyVisitor(FieldVisitorConvertToNumber<Float64>(), assert_cast<const ColumnConst &>(*col).getField());

        if (seconds < 0 || !std::isfinite(seconds))
            throw Exception(ErrorCodes::BAD_ARGUMENTS, "Cannot sleep infinite or negative amount of time (not implemented)");

        size_t size = col->size();

        /// We do not sleep if the columns is empty.
        if (size > 0)
        {
            /// When sleeping, the query cannot be cancelled. For ability to cancel query, we limit sleep time.
            if (max_microseconds && seconds * 1e6 > max_microseconds)
                throw Exception(ErrorCodes::TOO_SLOW, "The maximum sleep time is 3 seconds. Requested: {}", toString(seconds));

            if (!dry_run)
            {
                UInt64 count = (variant == FunctionSleepVariant::PerBlock ? 1 : size);
                UInt64 microseconds = static_cast<UInt64>(seconds * count * 1e6);

                if (max_microseconds && microseconds > max_microseconds)
                    throw Exception(ErrorCodes::TOO_SLOW,
                        "The maximum sleep time is 3 seconds. Requested: {} microseconds per block (of size {})",
                        microseconds, size);

                sleepForMicroseconds(microseconds);
                ProfileEvents::increment(ProfileEvents::SleepFunctionCalls, count);
                ProfileEvents::increment(ProfileEvents::SleepFunctionMicroseconds, microseconds);
            }
        }

        /// convertToFullColumn needed, because otherwise (constant expression case) function will not get called on each columns.
        return result_type->createColumnConst(size, 0u)->convertToFullColumnIfConst();
    }
};

}