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41 lines
933 B
C++
41 lines
933 B
C++
#pragma once
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#include <Parsers/IAST.h>
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#include <Interpreters/InDepthNodeVisitor.h>
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namespace DB
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{
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class ASTFunction;
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class ColumnsDescription;
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class ASTIdentifier;
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/* The Visitor is used to replace ALIAS by EXPRESSION when we refer to ALIAS
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* column in index definition.
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*
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* For example, if we have following create statement:
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* CREATE TABLE t
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* (
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* col UInt8,
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* col_alias ALIAS col + 1
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* INDEX idx (col_alias) TYPE minmax
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* ) ENGINE = MergeTree ORDER BY col;
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* we need call the visitor to replace `col_alias` by `col` + 1 when get index
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* description from index definition AST.
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*/
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class ReplaceAliasByExpressionMatcher
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{
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public:
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struct Data
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{
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const ColumnsDescription & columns;
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};
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static void visit(ASTPtr & ast, Data &);
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static void visit(const ASTIdentifier &, ASTPtr & ast, Data &);
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static bool needChildVisit(const ASTPtr &, const ASTPtr &) { return true; }
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};
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}
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