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31 lines
838 B
C++
31 lines
838 B
C++
#pragma once
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#include <Parsers/IAST.h>
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#include <Interpreters/InDepthNodeVisitor.h>
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#include "Interpreters/TreeRewriter.h"
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namespace DB
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{
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class ASTFunction;
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/** Optimize `uniq` into `count` over subquery.
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* Example: 'SELECT uniq(x ...) FROM (SELECT DISTINCT x ...)' to
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* Result: 'SELECT count() FROM (SELECT DISTINCT x ...)'
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*
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* Example: 'SELECT uniq(x ...) FROM (SELECT x ... GROUP BY x ...)' to
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* Result: 'SELECT count() FROM (SELECT x ... GROUP BY x ...)'
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*
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* Note that we can rewrite all uniq variants except uniqUpTo.
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*/
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class RewriteUniqToCountMatcher
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{
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public:
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struct Data {};
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static void visit(ASTPtr & ast, Data &);
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static bool needChildVisit(const ASTPtr &, const ASTPtr &) { return true; }
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};
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using RewriteUniqToCountVisitor = InDepthNodeVisitor<RewriteUniqToCountMatcher, true>;
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}
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