ClickHouse

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#include <Processors/QueryPlan/OffsetStep.h>
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#include <Processors/OffsetTransform.h>
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#include <QueryPipeline/QueryPipelineBuilder.h>
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#include <IO/Operators.h>
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#include <Common/JSONBuilder.h>
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namespace DB
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{
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static ITransformingStep::Traits getTraits()
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{
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    return ITransformingStep::Traits
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    {
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        {
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            .returns_single_stream = false,
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            .preserves_number_of_streams = true,
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            .preserves_sorting = true,
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        },
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        {
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            .preserves_number_of_rows = false,
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        }
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    };
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}
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OffsetStep::OffsetStep(const DataStream & input_stream_, size_t offset_)
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    : ITransformingStep(input_stream_, input_stream_.header, getTraits())
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    , offset(offset_)
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{
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}
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void OffsetStep::transformPipeline(QueryPipelineBuilder & pipeline, const BuildQueryPipelineSettings &)
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{
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    auto transform = std::make_shared<OffsetTransform>(
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            pipeline.getHeader(), offset, pipeline.getNumStreams());
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    pipeline.addTransform(std::move(transform));
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}
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void OffsetStep::describeActions(FormatSettings & settings) const
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{
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    settings.out << String(settings.offset, ' ') << "Offset " << offset << '\n';
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}
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void OffsetStep::describeActions(JSONBuilder::JSONMap & map) const
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{
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    map.add("Offset", offset);
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}
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}
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