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47 lines
1.2 KiB
C++
47 lines
1.2 KiB
C++
#pragma once
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#include <set>
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#include <Core/Block.h>
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#include <Parsers/IAST_fwd.h>
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namespace DB
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{
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class Context;
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class NamesAndTypesList;
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namespace VirtualColumnUtils
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{
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/// Adds to the select query section `WITH value AS column_name`, and uses func
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/// to wrap the value (if any)
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///
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/// For example:
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/// - `WITH 9000 as _port`.
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/// - `WITH toUInt16(9000) as _port`.
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void rewriteEntityInAst(ASTPtr ast, const String & column_name, const Field & value, const String & func = "");
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/// Leave in the block only the rows that fit under the WHERE clause and the PREWHERE clause of the query.
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/// Only elements of the outer conjunction are considered, depending only on the columns present in the block.
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/// Returns true if at least one row is discarded.
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void filterBlockWithQuery(const ASTPtr & query, Block & block, const Context & context);
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/// Extract from the input stream a set of `name` column values
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template <typename T>
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std::multiset<T> extractSingleValueFromBlock(const Block & block, const String & name)
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{
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std::multiset<T> res;
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const ColumnWithTypeAndName & data = block.getByName(name);
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size_t rows = block.rows();
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for (size_t i = 0; i < rows; ++i)
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res.insert((*data.column)[i].get<T>());
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return res;
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}
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}
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}
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