mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-12-11 17:02:25 +00:00
23 lines
584 B
C++
23 lines
584 B
C++
#pragma once
|
|
|
|
#include <Parsers/IAST.h>
|
|
#include <Interpreters/InDepthNodeVisitor.h>
|
|
#include "Interpreters/TreeRewriter.h"
|
|
|
|
namespace DB
|
|
{
|
|
|
|
class ASTFunction;
|
|
|
|
/// Really simple rewrite 'select countDistinct(a) from t' to 'select count(1) from (select a from t groupBy a)'
|
|
class RewriteCountDistinctFunctionMatcher
|
|
{
|
|
public:
|
|
struct Data {};
|
|
static void visit(ASTPtr & ast, Data &);
|
|
static bool needChildVisit(const ASTPtr &, const ASTPtr &) { return true; }
|
|
};
|
|
|
|
using RewriteCountDistinctFunctionVisitor = InDepthNodeVisitor<RewriteCountDistinctFunctionMatcher, true>;
|
|
}
|