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79 lines
1.9 KiB
C++
79 lines
1.9 KiB
C++
#pragma once
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#include <DB/Core/Block.h>
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namespace DB
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{
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namespace Conditional
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{
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/// Here is provided a way to incrementally build the null map of the result column
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/// of a multiIf invokation if its type is nullable.
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class NullMapBuilder final
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{
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public:
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/// Create a dummy builder when we don't need any builder, i.e. when the result
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/// of multiIf is not nullable.
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NullMapBuilder()
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: block{empty_block}
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{
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}
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/// This constructor takes the block that contains the original data received
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/// by multiIf, i.e. they have not been processed.
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NullMapBuilder(Block & block_)
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: block{block_}, row_count{block.rows()}
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{
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}
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/// Check whether the builder is dummy or not.
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operator bool() const { return block; }
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bool operator!() const { return !block; }
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/// Initialize the builder. For the non-trivial execution paths of multiIf.
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void init(const ColumnNumbers & args);
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/// Update the null map being built at the row that has just been processed
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/// by multiIf. The parameter index indicates the index of the column being
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/// checked for nullity. For non-trivial execution paths of multiIf.
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void update(size_t index, size_t row);
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/// Build the null map. The parameter index has the same meaning as above.
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/// For the trivial execution path of multiIf.
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void build(size_t index);
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/// Accessor needed to return the fully built null map.
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ColumnPtr getNullMap() const { return null_map; }
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private:
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/// Property of a column.
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enum Property
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{
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/// Neither nullable nor null.
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IS_ORDINARY = 0,
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/// Nullable column.
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IS_NULLABLE,
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/// Null column.
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IS_NULL
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};
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private:
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Block & block;
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/// Remember for each column representing an argument whether it is
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/// nullable, null, or neither of them. This avoids us many costly
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/// calls to virtual functions.
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PaddedPODArray<Property> cols_properties;
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ColumnPtr null_map;
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size_t row_count;
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private:
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static Block empty_block;
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};
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}
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}
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