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46 lines
1.4 KiB
C++
46 lines
1.4 KiB
C++
#pragma once
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#include <Parsers/IAST.h>
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namespace DB
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{
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/** Base class for AST, which can contain an alias (identifiers, literals, functions).
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*/
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class ASTWithAlias : public IAST
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{
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public:
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/// The alias, if any, or an empty string.
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String alias;
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/// If is true, getColumnName returns alias. Uses for aliases in former WITH section of SELECT query.
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/// Example: 'WITH pow(2, 2) as a SELECT pow(a, 2)' returns 'pow(a, 2)' instead of 'pow(pow(2, 2), 2)'
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bool prefer_alias_to_column_name = false;
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using IAST::IAST;
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void appendColumnName(WriteBuffer & ostr) const final;
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String getAliasOrColumnName() const override { return alias.empty() ? getColumnName() : alias; }
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String tryGetAlias() const override { return alias; }
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void setAlias(const String & to) override { alias = to; }
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/// Calls formatImplWithoutAlias, and also outputs an alias. If necessary, encloses the entire expression in brackets.
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void formatImpl(const FormatSettings & settings, FormatState & state, FormatStateStacked frame) const override final;
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virtual void formatImplWithoutAlias(const FormatSettings & settings, FormatState & state, FormatStateStacked frame) const = 0;
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protected:
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virtual void appendColumnNameImpl(WriteBuffer & ostr) const = 0;
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};
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/// helper for setting aliases and chaining result to other functions
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inline ASTPtr setAlias(ASTPtr ast, const String & alias)
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{
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ast->setAlias(alias);
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return ast;
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}
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}
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